Config - access Perl configuration information

- NAME
- SYNOPSIS
- DESCRIPTION
- EXAMPLE
- WARNING
- GLOSSARY

- _
- a
- b
- c
- C
- d
- e
- f
- g
- h
- i
- k
- l
- m
- M
- n
- o
- p
- P
- q
- r
- s
- t
- u
- v
- x
- z

- NOTE

# NAME

Config - access Perl configuration information

# SYNOPSIS

        use Config;
        if ($Config{'cc'} =~ /gcc/) {
            print "built by gcc\n";
        }

        use Config qw(myconfig config_sh config_vars);

        print myconfig();

        print config_sh();

        config_vars(qw(osname archname));

# DESCRIPTION

The Config module contains all the information that was available to the `Configure` program at Perl build time (over 900 values).

Shell variables from the config.sh file (written by Configure) are stored in the readonly-variable `%Config`, indexed by their names.

Values stored in config.sh as 'undef' are returned as undefined values. The perl `exists` function can be used to check if a named variable exists.

`myconfig()`
  Returns a textual summary of the major perl configuration values. See also `-V` in Switches in the perlrun manpage.

`config_sh()`
  Returns the entire perl configuration information in the form of the original config.sh shell variable assignment script.

`config_vars(@names)`
  Prints to STDOUT the values of the named configuration variable. Each is printed on a separate line in the form:

        name='value';

  Names which are unknown are output as `name='UNKNOWN';`. See also `-V:name` in Switches in the perlrun manpage.

# EXAMPLE

Here's a more sophisticated example of using %Config:

        use Config;
        use strict;

        my %sig_num;
        my @sig_name;
        unless($Config{sig_name} && $Config{sig_num}) {
            die "No sigs?";
        } else {
            my @names = split ' ', $Config{sig_name};
            @sig_num{@names} = split ' ', $Config{sig_num};
            foreach (@names) {
                $sig_name[$sig_num{$_}] ||= $_;
            }
        }

        print "signal #17 = $sig_name[17]\n";
        if ($sig_num{ALRM}) {
            print "SIGALRM is $sig_num{ALRM}\n";
        }

# WARNING

Because this information is not stored within the perl executable itself it is possible (but unlikely) that the information does not relate to the actual perl binary which is being used to access it.

The Config module is installed into the architecture and version specific library directory ($Config{installarchlib}) and it checks the perl version number when loaded.

The values stored in config.sh may be either single-quoted or double-quoted. Double-quoted strings are handy for those cases where you need to include escape sequences in the strings. To avoid runtime variable interpolation, any `$` and `@` characters are replaced by `\$` and `\@`, respectively. This isn't foolproof, of course, so don't embed `\$` or `\@` in double-quoted strings unless you're willing to deal with the consequences. (The slashes will end up escaped and the `$` or `@` will trigger variable interpolation)

# GLOSSARY

Most `Config` variables are determined by the `Configure` script on platforms supported by it (which is most UNIX platforms). Some platforms have custom-made `Config` variables, and may thus not have some of the variables described below, or may have extraneous variables specific to that particular port. See the port specific documentation in such cases.

## _

`_a`
  From Unix.U:

  This variable defines the extension used for ordinary libraries. For unix, it is .a. The . is included. Other possible values include .lib.

`_exe`
  From Unix.U:

  This variable defines the extension used for executable files. For unix it is empty. Other possible values include .exe.

`_o`
  From Unix.U:

  This variable defines the extension used for object files. For unix, it is .o. The . is included. Other possible values include .obj.

## a

`afs`
  From afs.U:

  This variable is set to `true` if `AFS` (Andrew File System) is used on the system, `false` otherwise. It is possible to override this with a hint value or command line option, but you'd better know what you are doing.

`alignbytes`
  From alignbytes.U:

  This variable holds the number of bytes required to align a double-- or a long double when applicable. Usual values are 2, 4 and 8. The default is eight, for safety.

`ansi2knr`
  From ansi2knr.U:

  This variable is set if the user needs to run ansi2knr. Currently, this is not supported, so we just abort.

`aphostname`
  From d_gethname.U:

  This variable contains the command which can be used to compute the host name. The command is fully qualified by its absolute path, to make it safe when used by a process with super-user privileges.

`api_revision`
  From patchlevel.U:

  The three variables, api_revision, api_version, and api_subversion, specify the version of the oldest perl binary compatible with the present perl. In a full version string such as 5.6.1, api_revision is the `5`. Prior to 5.5.640, the format was a floating point number, like 5.00563.

              F<perl.c>:incpush() and F<lib/lib.pm> will automatically search in

              $F<sitelib/.>. for older directories back to the limit specified
      by these api_ variables.  This is only useful if you have a
      perl library directory tree structured like the default one.
      See C<INSTALL> for how this works.  The versioned site_perl
      directory was introduced in 5.005, so that is the lowest
      possible value.  The version list appropriate for the current
      system is determined in F<inc_version_list.U>.

              C<XXX> To do:  Since compatibility can depend on compile time

              options (such as bincompat, longlong, F<etc.>) it should
      (perhaps) be set by Configure, but currently it isn't.
      Currently, we read a hard-wired value from F<patchlevel.h>.
      Perhaps what we ought to do is take the hard-wired value from
      F<patchlevel.h> but then modify it if the current Configure
      options warrant.  F<patchlevel.h> then would use an #ifdef guard.

`api_subversion`
  From patchlevel.U:

  The three variables, api_revision, api_version, and api_subversion, specify the version of the oldest perl binary compatible with the present perl. In a full version string such as 5.6.1, api_subversion is the `1`. See api_revision for full details.

`api_version`
  From patchlevel.U:

  The three variables, api_revision, api_version, and api_subversion, specify the version of the oldest perl binary compatible with the present perl. In a full version string such as 5.6.1, api_version is the `6`. See api_revision for full details. As a special case, 5.5.0 is rendered in the old-style as 5.005. (In the 5.005_0x maintenance series, this was the only versioned directory in $sitelib.)

`api_versionstring`
  From patchlevel.U:

  This variable combines api_revision, api_version, and api_subversion in a format such as 5.6.1 (or 5_6_1) suitable for use as a directory name. This is filesystem dependent.

`ar`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the ar program. After Configure runs, the value is reset to a plain `ar` and is not useful.

`archlib`
  From archlib.U:

  This variable holds the name of the directory in which the user wants to put architecture-dependent public library files for $package. It is most often a local directory such as /usr/local/lib. Programs using this variable must be prepared to deal with filename expansion.

`archlibexp`
  From archlib.U:

  This variable is the same as the archlib variable, but is filename expanded at configuration time, for convenient use.

`archname64`
  From use64bits.U:

  This variable is used for the 64-bitness part of $archname.

`archname`
  From archname.U:

  This variable is a short name to characterize the current architecture. It is used mainly to construct the default archlib.

`archobjs`
  From Unix.U:

  This variable defines any additional objects that must be linked in with the program on this architecture. On unix, it is usually empty. It is typically used to include emulations of unix calls or other facilities. For perl on OS/2, for example, this would include os2/os2.obj.

`awk`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the awk program. After Configure runs, the value is reset to a plain `awk` and is not useful.

## b

`baserev`
  From baserev.U:

  The base revision level of this package, from the .package file.

`bash`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`bin`
  From bin.U:

  This variable holds the name of the directory in which the user wants to put publicly executable images for the package in question. It is most often a local directory such as /usr/local/bin. Programs using this variable must be prepared to deal with ~name substitution.

`bincompat5005`
  From bincompat5005.U:

  This variable contains y if this version of Perl should be binary-compatible with Perl 5.005.

`binexp`
  From bin.U:

  This is the same as the bin variable, but is filename expanded at configuration time, for use in your makefiles.

`bison`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`byacc`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the byacc program. After Configure runs, the value is reset to a plain `byacc` and is not useful.

`byteorder`
  From byteorder.U:

  This variable holds the byte order. In the following, larger digits indicate more significance. The variable byteorder is either 4321 on a big-endian machine, or 1234 on a little-endian, or 87654321 on a Cray ... or 3412 with weird order !

## c

`c`
  From n.U:

  This variable contains the \c string if that is what causes the echo command to suppress newline. Otherwise it is null. Correct usage is $echo $n ``prompt for a question: $c''.

`castflags`
  From d_castneg.U:

  This variable contains a flag that precise difficulties the compiler has casting odd floating values to unsigned long: 0 = ok 1 = couldn't cast < 0 2 = couldn't cast >= 0x80000000 4 = couldn't cast in argument expression list

`cat`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the cat program. After Configure runs, the value is reset to a plain `cat` and is not useful.

`cc`
  From cc.U:

  This variable holds the name of a command to execute a C compiler which can resolve multiple global references that happen to have the same name. Usual values are `cc` and `gcc`. Fervent `ANSI` compilers may be called `c89`. `AIX` has xlc.

`cccdlflags`
  From dlsrc.U:

  This variable contains any special flags that might need to be passed with `cc -c` to compile modules to be used to create a shared library that will be used for dynamic loading. For hpux, this should be +z. It is up to the makefile to use it.

`ccdlflags`
  From dlsrc.U:

  This variable contains any special flags that might need to be passed to cc to link with a shared library for dynamic loading. It is up to the makefile to use it. For sunos 4.1, it should be empty.

`ccflags`
  From ccflags.U:

  This variable contains any additional C compiler flags desired by the user. It is up to the Makefile to use this.

`ccflags_uselargefiles`
  From uselfs.U:

  This variable contains the compiler flags needed by large file builds and added to ccflags by hints files.

`ccname`
  From Checkcc.U:

  This can set either by hints files or by Configure. If using gcc, this is gcc, and if not, usually equal to cc, unimpressive, no? Some platforms, however, make good use of this by storing the flavor of the C compiler being used here. For example if using the Sun WorkShop suite, ccname will be `workshop`.

`ccsymbols`
  From Cppsym.U:

  The variable contains the symbols defined by the C compiler alone. The symbols defined by cpp or by cc when it calls cpp are not in this list, see cppsymbols and cppccsymbols. The list is a space-separated list of symbol=value tokens.

`ccversion`
  From Checkcc.U:

  This can set either by hints files or by Configure. If using a (non-gcc) vendor cc, this variable may contain a version for the compiler.

`cf_by`
  From cf_who.U:

  Login name of the person who ran the Configure script and answered the questions. This is used to tag both config.sh and config_h.SH.

`cf_email`
  From cf_email.U:

  Electronic mail address of the person who ran Configure. This can be used by units that require the user's e-mail, like MailList.U.

`cf_time`
  From cf_who.U:

  Holds the output of the `date` command when the configuration file was produced. This is used to tag both config.sh and config_h.SH.

`charsize`
  From charsize.U:

  This variable contains the value of the `CHARSIZE` symbol, which indicates to the C program how many bytes there are in a character.

`chgrp`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`chmod`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`chown`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`clocktype`
  From d_times.U:

  This variable holds the type returned by times(). It can be long, or clock_t on `BSD` sites (in which case <sys/types.h> should be included).

`comm`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the comm program. After Configure runs, the value is reset to a plain `comm` and is not useful.

`compress`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

## C

`CONFIGDOTSH`
  From Oldsyms.U:

  This is set to `true` in config.sh so that a shell script sourcing config.sh can tell if it has been sourced already.

`contains`
  From contains.U:

  This variable holds the command to do a grep with a proper return status. On most sane systems it is simply `grep`. On insane systems it is a grep followed by a cat followed by a test. This variable is primarily for the use of other Configure units.

`cp`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the cp program. After Configure runs, the value is reset to a plain `cp` and is not useful.

`cpio`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`cpp`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the cpp program. After Configure runs, the value is reset to a plain `cpp` and is not useful.

`cpp_stuff`
  From cpp_stuff.U:

  This variable contains an identification of the catenation mechanism used by the C preprocessor.

`cppccsymbols`
  From Cppsym.U:

  The variable contains the symbols defined by the C compiler when it calls cpp. The symbols defined by the cc alone or cpp alone are not in this list, see ccsymbols and cppsymbols. The list is a space-separated list of symbol=value tokens.

`cppflags`
  From ccflags.U:

  This variable holds the flags that will be passed to the C pre- processor. It is up to the Makefile to use it.

`cpplast`
  From cppstdin.U:

  This variable has the same functionality as cppminus, only it applies to cpprun and not cppstdin.

`cppminus`
  From cppstdin.U:

  This variable contains the second part of the string which will invoke the C preprocessor on the standard input and produce to standard output. This variable will have the value `-` if cppstdin needs a minus to specify standard input, otherwise the value is ``''.

`cpprun`
  From cppstdin.U:

  This variable contains the command which will invoke a C preprocessor on standard input and put the output to stdout. It is guaranteed not to be a wrapper and may be a null string if no preprocessor can be made directly available. This preprocessor might be different from the one used by the C compiler. Don't forget to append cpplast after the preprocessor options.

`cppstdin`
  From cppstdin.U:

  This variable contains the command which will invoke the C preprocessor on standard input and put the output to stdout. It is primarily used by other Configure units that ask about preprocessor symbols.

`cppsymbols`
  From Cppsym.U:

  The variable contains the symbols defined by the C preprocessor alone. The symbols defined by cc or by cc when it calls cpp are not in this list, see ccsymbols and cppccsymbols. The list is a space-separated list of symbol=value tokens.

`crosscompile`
  From crosscompile.U:

  This variable conditionally defines the `CROSSCOMPILE` symbol which signifies that the build process is be a cross-compilation. This is normally set by hints files or from Configure command line.

`cryptlib`
  From d_crypt.U:

  This variable holds -lcrypt or the path to a libcrypt.a archive if the `crypt()` function is not defined in the standard C library. It is up to the Makefile to use this.

`csh`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the csh program. After Configure runs, the value is reset to a plain `csh` and is not useful.

## d

`d__fwalk`
  From d__fwalk.U:

  This variable conditionally defines `HAS__FWALK` if `_fwalk()` is available to apply a function to all the file handles.

`d_access`
  From d_access.U:

  This variable conditionally defines `HAS_ACCESS` if the `access()` system call is available to check for access permissions using real IDs.

`d_accessx`
  From d_accessx.U:

  This variable conditionally defines the `HAS_ACCESSX` symbol, which indicates to the C program that the `accessx()` routine is available.

`d_alarm`
  From d_alarm.U:

  This variable conditionally defines the `HAS_ALARM` symbol, which indicates to the C program that the `alarm()` routine is available.

`d_archlib`
  From archlib.U:

  This variable conditionally defines `ARCHLIB` to hold the pathname of architecture-dependent library files for $package. If $archlib is the same as $privlib, then this is set to undef.

`d_atolf`
  From atolf.U:

  This variable conditionally defines the `HAS_ATOLF` symbol, which indicates to the C program that the `atolf()` routine is available.

`d_atoll`
  From atoll.U:

  This variable conditionally defines the `HAS_ATOLL` symbol, which indicates to the C program that the `atoll()` routine is available.

`d_attribut`
  From d_attribut.U:

  This variable conditionally defines `HASATTRIBUTE`, which indicates the C compiler can check for function attributes, such as printf formats.

`d_bcmp`
  From d_bcmp.U:

  This variable conditionally defines the `HAS_BCMP` symbol if the `bcmp()` routine is available to compare strings.

`d_bcopy`
  From d_bcopy.U:

  This variable conditionally defines the `HAS_BCOPY` symbol if the `bcopy()` routine is available to copy strings.

`d_bincompat5005`
  From bincompat5005.U:

  This variable conditionally defines BINCOMPAT5005 so that embed.h can take special action if this version of Perl should be binary-compatible with Perl 5.005. This is impossible for builds that use features like threads and multiplicity it is always $undef for those versions.

`d_bsd`
  From Guess.U:

  This symbol conditionally defines the symbol `BSD` when running on a `BSD` system.

`d_bsdgetpgrp`
  From d_getpgrp.U:

  This variable conditionally defines `USE_BSD_GETPGRP` if getpgrp needs one arguments whereas `USG` one needs none.

`d_bsdsetpgrp`
  From d_setpgrp.U:

  This variable conditionally defines `USE_BSD_SETPGRP` if setpgrp needs two arguments whereas `USG` one needs none. See also d_setpgid for a `POSIX` interface.

`d_bzero`
  From d_bzero.U:

  This variable conditionally defines the `HAS_BZERO` symbol if the `bzero()` routine is available to set memory to 0.

`d_casti32`
  From d_casti32.U:

  This variable conditionally defines CASTI32, which indicates whether the C compiler can cast large floats to 32-bit ints.

`d_castneg`
  From d_castneg.U:

  This variable conditionally defines `CASTNEG`, which indicates wether the C compiler can cast negative float to unsigned.

`d_charvspr`
  From d_vprintf.U:

  This variable conditionally defines `CHARVSPRINTF` if this system has vsprintf returning type (char*). The trend seems to be to declare it as ``int vsprintf()''.

`d_chown`
  From d_chown.U:

  This variable conditionally defines the `HAS_CHOWN` symbol, which indicates to the C program that the `chown()` routine is available.

`d_chroot`
  From d_chroot.U:

  This variable conditionally defines the `HAS_CHROOT` symbol, which indicates to the C program that the `chroot()` routine is available.

`d_chsize`
  From d_chsize.U:

  This variable conditionally defines the `CHSIZE` symbol, which indicates to the C program that the `chsize()` routine is available to truncate files. You might need a -lx to get this routine.

`d_closedir`
  From d_closedir.U:

  This variable conditionally defines `HAS_CLOSEDIR` if `closedir()` is available.

`d_const`
  From d_const.U:

  This variable conditionally defines the `HASCONST` symbol, which indicates to the C program that this C compiler knows about the const type.

`d_crypt`
  From d_crypt.U:

  This variable conditionally defines the `CRYPT` symbol, which indicates to the C program that the `crypt()` routine is available to encrypt passwords and the like.

`d_csh`
  From d_csh.U:

  This variable conditionally defines the `CSH` symbol, which indicates to the C program that the C-shell exists.

`d_cuserid`
  From d_cuserid.U:

  This variable conditionally defines the `HAS_CUSERID` symbol, which indicates to the C program that the `cuserid()` routine is available to get character login names.

`d_dbl_dig`
  From d_dbl_dig.U:

  This variable conditionally defines d_dbl_dig if this system's header files provide `DBL_DIG`, which is the number of significant digits in a double precision number.

`d_difftime`
  From d_difftime.U:

  This variable conditionally defines the `HAS_DIFFTIME` symbol, which indicates to the C program that the `difftime()` routine is available.

`d_dirnamlen`
  From i_dirent.U:

  This variable conditionally defines `DIRNAMLEN`, which indicates to the C program that the length of directory entry names is provided by a d_namelen field.

`d_dlerror`
  From d_dlerror.U:

  This variable conditionally defines the `HAS_DLERROR` symbol, which indicates to the C program that the `dlerror()` routine is available.

`d_dlopen`
  From d_dlopen.U:

  This variable conditionally defines the `HAS_DLOPEN` symbol, which indicates to the C program that the `dlopen()` routine is available.

`d_dlsymun`
  From d_dlsymun.U:

  This variable conditionally defines `DLSYM_NEEDS_UNDERSCORE`, which indicates that we need to prepend an underscore to the symbol name before calling dlsym().

`d_dosuid`
  From d_dosuid.U:

  This variable conditionally defines the symbol `DOSUID`, which tells the C program that it should insert setuid emulation code on hosts which have setuid #! scripts disabled.

`d_drand48proto`
  From d_drand48proto.U:

  This variable conditionally defines the HAS_DRAND48_PROTO symbol, which indicates to the C program that the system provides a prototype for the `drand48()` function. Otherwise, it is up to the program to supply one.

`d_dup2`
  From d_dup2.U:

  This variable conditionally defines HAS_DUP2 if `dup2()` is available to duplicate file descriptors.

`d_eaccess`
  From d_eaccess.U:

  This variable conditionally defines the `HAS_EACCESS` symbol, which indicates to the C program that the `eaccess()` routine is available.

`d_endgrent`
  From d_endgrent.U:

  This variable conditionally defines the `HAS_ENDGRENT` symbol, which indicates to the C program that the `endgrent()` routine is available for sequential access of the group database.

`d_endhent`
  From d_endhent.U:

  This variable conditionally defines `HAS_ENDHOSTENT` if `endhostent()` is available to close whatever was being used for host queries.

`d_endnent`
  From d_endnent.U:

  This variable conditionally defines `HAS_ENDNETENT` if `endnetent()` is available to close whatever was being used for network queries.

`d_endpent`
  From d_endpent.U:

  This variable conditionally defines `HAS_ENDPROTOENT` if `endprotoent()` is available to close whatever was being used for protocol queries.

`d_endpwent`
  From d_endpwent.U:

  This variable conditionally defines the `HAS_ENDPWENT` symbol, which indicates to the C program that the `endpwent()` routine is available for sequential access of the passwd database.

`d_endsent`
  From d_endsent.U:

  This variable conditionally defines `HAS_ENDSERVENT` if `endservent()` is available to close whatever was being used for service queries.

`d_eofnblk`
  From nblock_io.U:

  This variable conditionally defines `EOF_NONBLOCK` if `EOF` can be seen when reading from a non-blocking I/O source.

`d_eunice`
  From Guess.U:

  This variable conditionally defines the symbols `EUNICE` and `VAX`, which alerts the C program that it must deal with ideosyncracies of `VMS`.

`d_fchmod`
  From d_fchmod.U:

  This variable conditionally defines the `HAS_FCHMOD` symbol, which indicates to the C program that the `fchmod()` routine is available to change mode of opened files.

`d_fchown`
  From d_fchown.U:

  This variable conditionally defines the `HAS_FCHOWN` symbol, which indicates to the C program that the `fchown()` routine is available to change ownership of opened files.

`d_fcntl`
  From d_fcntl.U:

  This variable conditionally defines the `HAS_FCNTL` symbol, and indicates whether the `fcntl()` function exists

`d_fcntl_can_lock`
  From d_fcntl_can_lock.U:

  This variable conditionally defines the `FCNTL_CAN_LOCK` symbol and indicates whether file locking with `fcntl()` works.

`d_fd_macros`
  From d_fd_set.U:

  This variable contains the eventual value of the `HAS_FD_MACROS` symbol, which indicates if your C compiler knows about the macros which manipulate an fd_set.

`d_fd_set`
  From d_fd_set.U:

  This variable contains the eventual value of the `HAS_FD_SET` symbol, which indicates if your C compiler knows about the fd_set typedef.

`d_fds_bits`
  From d_fd_set.U:

  This variable contains the eventual value of the `HAS_FDS_BITS` symbol, which indicates if your fd_set typedef contains the fds_bits member. If you have an fd_set typedef, but the dweebs who installed it did a half-fast job and neglected to provide the macros to manipulate an fd_set, `HAS_FDS_BITS` will let us know how to fix the gaffe.

`d_fgetpos`
  From d_fgetpos.U:

  This variable conditionally defines `HAS_FGETPOS` if `fgetpos()` is available to get the file position indicator.

`d_flexfnam`
  From d_flexfnam.U:

  This variable conditionally defines the `FLEXFILENAMES` symbol, which indicates that the system supports filenames longer than 14 characters.

`d_flock`
  From d_flock.U:

  This variable conditionally defines `HAS_FLOCK` if `flock()` is available to do file locking.

`d_fork`
  From d_fork.U:

  This variable conditionally defines the `HAS_FORK` symbol, which indicates to the C program that the `fork()` routine is available.

`d_fpathconf`
  From d_pathconf.U:

  This variable conditionally defines the `HAS_FPATHCONF` symbol, which indicates to the C program that the `pathconf()` routine is available to determine file-system related limits and options associated with a given open file descriptor.

`d_fpos64_t`
  From d_fpos64_t.U:

  This symbol will be defined if the C compiler supports fpos64_t.

`d_frexpl`
  From d_frexpl.U:

  This variable conditionally defines the `HAS_FREXPL` symbol, which indicates to the C program that the `frexpl()` routine is available.

`d_fs_data_s`
  From d_fs_data_s.U:

  This variable conditionally defines the `HAS_STRUCT_FS_DATA` symbol, which indicates that the struct fs_data is supported.

`d_fseeko`
  From d_fseeko.U:

  This variable conditionally defines the `HAS_FSEEKO` symbol, which indicates to the C program that the `fseeko()` routine is available.

`d_fsetpos`
  From d_fsetpos.U:

  This variable conditionally defines `HAS_FSETPOS` if `fsetpos()` is available to set the file position indicator.

`d_fstatfs`
  From d_fstatfs.U:

  This variable conditionally defines the `HAS_FSTATFS` symbol, which indicates to the C program that the `fstatfs()` routine is available.

`d_fstatvfs`
  From d_statvfs.U:

  This variable conditionally defines the `HAS_FSTATVFS` symbol, which indicates to the C program that the `fstatvfs()` routine is available.

`d_fsync`
  From d_fsync.U:

  This variable conditionally defines the `HAS_FSYNC` symbol, which indicates to the C program that the `fsync()` routine is available.

`d_ftello`
  From d_ftello.U:

  This variable conditionally defines the `HAS_FTELLO` symbol, which indicates to the C program that the `ftello()` routine is available.

`d_ftime`
  From d_ftime.U:

  This variable conditionally defines the `HAS_FTIME` symbol, which indicates that the `ftime()` routine exists. The `ftime()` routine is basically a sub-second accuracy clock.

`d_Gconvert`
  From d_gconvert.U:

  This variable holds what Gconvert is defined as to convert floating point numbers into strings. It could be `gconvert` or a more `complex` macro emulating gconvert with `gcvt()` or sprintf. Possible values are: d_Gconvert=`gconvert((x),(n),(t),(b))` d_Gconvert=`gcvt((x),(n),(b))` d_Gconvert=`sprintf((b),%.*g,(n),(x))`

`d_getcwd`
  From d_getcwd.U:

  This variable conditionally defines the `HAS_GETCWD` symbol, which indicates to the C program that the `getcwd()` routine is available to get the current working directory.

`d_getespwnam`
  From d_getespwnam.U:

  This variable conditionally defines `HAS_GETESPWNAM` if `getespwnam()` is available to retrieve enchanced (shadow) password entries by name.

`d_getfsstat`
  From d_getfsstat.U:

  This variable conditionally defines the `HAS_GETFSSTAT` symbol, which indicates to the C program that the `getfsstat()` routine is available.

`d_getgrent`
  From d_getgrent.U:

  This variable conditionally defines the `HAS_GETGRENT` symbol, which indicates to the C program that the `getgrent()` routine is available for sequential access of the group database.

`d_getgrps`
  From d_getgrps.U:

  This variable conditionally defines the `HAS_GETGROUPS` symbol, which indicates to the C program that the `getgroups()` routine is available to get the list of process groups.

`d_gethbyaddr`
  From d_gethbyad.U:

  This variable conditionally defines the `HAS_GETHOSTBYADDR` symbol, which indicates to the C program that the `gethostbyaddr()` routine is available to look up hosts by their `IP` addresses.

`d_gethbyname`
  From d_gethbynm.U:

  This variable conditionally defines the `HAS_GETHOSTBYNAME` symbol, which indicates to the C program that the `gethostbyname()` routine is available to look up host names in some data base or other.

`d_gethent`
  From d_gethent.U:

  This variable conditionally defines `HAS_GETHOSTENT` if `gethostent()` is available to look up host names in some data base or another.

`d_gethname`
  From d_gethname.U:

  This variable conditionally defines the `HAS_GETHOSTNAME` symbol, which indicates to the C program that the `gethostname()` routine may be used to derive the host name.

`d_gethostprotos`
  From d_gethostprotos.U:

  This variable conditionally defines the `HAS_GETHOST_PROTOS` symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various gethost*() functions. See also netdbtype.U for probing for various netdb types.

`d_getlogin`
  From d_getlogin.U:

  This variable conditionally defines the `HAS_GETLOGIN` symbol, which indicates to the C program that the `getlogin()` routine is available to get the login name.

`d_getmnt`
  From d_getmnt.U:

  This variable conditionally defines the `HAS_GETMNT` symbol, which indicates to the C program that the `getmnt()` routine is available to retrieve one or more mount info blocks by filename.

`d_getmntent`
  From d_getmntent.U:

  This variable conditionally defines the `HAS_GETMNTENT` symbol, which indicates to the C program that the `getmntent()` routine is available to iterate through mounted files to get their mount info.

`d_getnbyaddr`
  From d_getnbyad.U:

  This variable conditionally defines the `HAS_GETNETBYADDR` symbol, which indicates to the C program that the `getnetbyaddr()` routine is available to look up networks by their `IP` addresses.

`d_getnbyname`
  From d_getnbynm.U:

  This variable conditionally defines the `HAS_GETNETBYNAME` symbol, which indicates to the C program that the `getnetbyname()` routine is available to look up networks by their names.

`d_getnent`
  From d_getnent.U:

  This variable conditionally defines `HAS_GETNETENT` if `getnetent()` is available to look up network names in some data base or another.

`d_getnetprotos`
  From d_getnetprotos.U:

  This variable conditionally defines the `HAS_GETNET_PROTOS` symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various getnet*() functions. See also netdbtype.U for probing for various netdb types.

`d_getpagsz`
  From d_getpagsz.U:

  This variable conditionally defines `HAS_GETPAGESIZE` if `getpagesize()` is available to get the system page size.

`d_getpbyname`
  From d_getprotby.U:

  This variable conditionally defines the `HAS_GETPROTOBYNAME` symbol, which indicates to the C program that the `getprotobyname()` routine is available to look up protocols by their name.

`d_getpbynumber`
  From d_getprotby.U:

  This variable conditionally defines the `HAS_GETPROTOBYNUMBER` symbol, which indicates to the C program that the `getprotobynumber()` routine is available to look up protocols by their number.

`d_getpent`
  From d_getpent.U:

  This variable conditionally defines `HAS_GETPROTOENT` if `getprotoent()` is available to look up protocols in some data base or another.

`d_getpgid`
  From d_getpgid.U:

  This variable conditionally defines the `HAS_GETPGID` symbol, which indicates to the C program that the `getpgid(pid)` function is available to get the process group id.

`d_getpgrp2`
  From d_getpgrp2.U:

  This variable conditionally defines the HAS_GETPGRP2 symbol, which indicates to the C program that the `getpgrp2()` (as in DG/`UX`) routine is available to get the current process group.

`d_getpgrp`
  From d_getpgrp.U:

  This variable conditionally defines `HAS_GETPGRP` if `getpgrp()` is available to get the current process group.

`d_getppid`
  From d_getppid.U:

  This variable conditionally defines the `HAS_GETPPID` symbol, which indicates to the C program that the `getppid()` routine is available to get the parent process `ID`.

`d_getprior`
  From d_getprior.U:

  This variable conditionally defines `HAS_GETPRIORITY` if `getpriority()` is available to get a process's priority.

`d_getprotoprotos`
  From d_getprotoprotos.U:

  This variable conditionally defines the `HAS_GETPROTO_PROTOS` symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various getproto*() functions. See also netdbtype.U for probing for various netdb types.

`d_getprpwnam`
  From d_getprpwnam.U:

  This variable conditionally defines `HAS_GETPRPWNAM` if `getprpwnam()` is available to retrieve protected (shadow) password entries by name.

`d_getpwent`
  From d_getpwent.U:

  This variable conditionally defines the `HAS_GETPWENT` symbol, which indicates to the C program that the `getpwent()` routine is available for sequential access of the passwd database.

`d_getsbyname`
  From d_getsrvby.U:

  This variable conditionally defines the `HAS_GETSERVBYNAME` symbol, which indicates to the C program that the `getservbyname()` routine is available to look up services by their name.

`d_getsbyport`
  From d_getsrvby.U:

  This variable conditionally defines the `HAS_GETSERVBYPORT` symbol, which indicates to the C program that the `getservbyport()` routine is available to look up services by their port.

`d_getsent`
  From d_getsent.U:

  This variable conditionally defines `HAS_GETSERVENT` if `getservent()` is available to look up network services in some data base or another.

`d_getservprotos`
  From d_getservprotos.U:

  This variable conditionally defines the `HAS_GETSERV_PROTOS` symbol, which indicates to the C program that <netdb.h> supplies prototypes for the various getserv*() functions. See also netdbtype.U for probing for various netdb types.

`d_getspnam`
  From d_getspnam.U:

  This variable conditionally defines `HAS_GETSPNAM` if `getspnam()` is available to retrieve SysV shadow password entries by name.

`d_gettimeod`
  From d_ftime.U:

  This variable conditionally defines the `HAS_GETTIMEOFDAY` symbol, which indicates that the `gettimeofday()` system call exists (to obtain a sub-second accuracy clock). You should probably include <sys/resource.h>.

`d_gnulibc`
  From d_gnulibc.U:

  Defined if we're dealing with the `GNU` C Library.

`d_grpasswd`
  From i_grp.U:

  This variable conditionally defines `GRPASSWD`, which indicates that struct group in <grp.h> contains gr_passwd.

`d_hasmntopt`
  From d_hasmntopt.U:

  This variable conditionally defines the `HAS_HASMNTOPT` symbol, which indicates to the C program that the `hasmntopt()` routine is available to query the mount options of file systems.

`d_htonl`
  From d_htonl.U:

  This variable conditionally defines `HAS_HTONL` if `htonl()` and its friends are available to do network order byte swapping.

`d_iconv`
  From d_iconv.U:

  This variable conditionally defines the `HAS_ICONV` symbol, which indicates to the C program that the `iconv()` routine is available.

`d_index`
  From d_strchr.U:

  This variable conditionally defines `HAS_INDEX` if `index()` and `rindex()` are available for string searching.

`d_inetaton`
  From d_inetaton.U:

  This variable conditionally defines the `HAS_INET_ATON` symbol, which indicates to the C program that the `inet_aton()` function is available to parse `IP` address `dotted-quad` strings.

`d_int64_t`
  From d_int64_t.U:

  This symbol will be defined if the C compiler supports int64_t.

`d_isascii`
  From d_isascii.U:

  This variable conditionally defines the `HAS_ISASCII` constant, which indicates to the C program that `isascii()` is available.

`d_isnan`
  From d_isnan.U:

  This variable conditionally defines the `HAS_ISNAN` symbol, which indicates to the C program that the `isnan()` routine is available.

`d_isnanl`
  From d_isnanl.U:

  This variable conditionally defines the `HAS_ISNANL` symbol, which indicates to the C program that the `isnanl()` routine is available.

`d_killpg`
  From d_killpg.U:

  This variable conditionally defines the `HAS_KILLPG` symbol, which indicates to the C program that the `killpg()` routine is available to kill process groups.

`d_lchown`
  From d_lchown.U:

  This variable conditionally defines the `HAS_LCHOWN` symbol, which indicates to the C program that the `lchown()` routine is available to operate on a symbolic link (instead of following the link).

`d_ldbl_dig`
  From d_ldbl_dig.U:

  This variable conditionally defines d_ldbl_dig if this system's header files provide `LDBL_DIG`, which is the number of significant digits in a long double precision number.

`d_link`
  From d_link.U:

  This variable conditionally defines `HAS_LINK` if `link()` is available to create hard links.

`d_locconv`
  From d_locconv.U:

  This variable conditionally defines `HAS_LOCALECONV` if `localeconv()` is available for numeric and monetary formatting conventions.

`d_lockf`
  From d_lockf.U:

  This variable conditionally defines `HAS_LOCKF` if `lockf()` is available to do file locking.

`d_longdbl`
  From d_longdbl.U:

  This variable conditionally defines `HAS_LONG_DOUBLE` if the long double type is supported.

`d_longlong`
  From d_longlong.U:

  This variable conditionally defines `HAS_LONG_LONG` if the long long type is supported.

`d_lseekproto`
  From d_lseekproto.U:

  This variable conditionally defines the `HAS_LSEEK_PROTO` symbol, which indicates to the C program that the system provides a prototype for the `lseek()` function. Otherwise, it is up to the program to supply one.

`d_lstat`
  From d_lstat.U:

  This variable conditionally defines `HAS_LSTAT` if `lstat()` is available to do file stats on symbolic links.

`d_madvise`
  From d_madvise.U:

  This variable conditionally defines `HAS_MADVISE` if `madvise()` is available to map a file into memory.

`d_mblen`
  From d_mblen.U:

  This variable conditionally defines the `HAS_MBLEN` symbol, which indicates to the C program that the `mblen()` routine is available to find the number of bytes in a multibye character.

`d_mbstowcs`
  From d_mbstowcs.U:

  This variable conditionally defines the `HAS_MBSTOWCS` symbol, which indicates to the C program that the `mbstowcs()` routine is available to convert a multibyte string into a wide character string.

`d_mbtowc`
  From d_mbtowc.U:

  This variable conditionally defines the `HAS_MBTOWC` symbol, which indicates to the C program that the `mbtowc()` routine is available to convert multibyte to a wide character.

`d_memchr`
  From d_memchr.U:

  This variable conditionally defines the `HAS_MEMCHR` symbol, which indicates to the C program that the `memchr()` routine is available to locate characters within a C string.

`d_memcmp`
  From d_memcmp.U:

  This variable conditionally defines the `HAS_MEMCMP` symbol, which indicates to the C program that the `memcmp()` routine is available to compare blocks of memory.

`d_memcpy`
  From d_memcpy.U:

  This variable conditionally defines the `HAS_MEMCPY` symbol, which indicates to the C program that the `memcpy()` routine is available to copy blocks of memory.

`d_memmove`
  From d_memmove.U:

  This variable conditionally defines the `HAS_MEMMOVE` symbol, which indicates to the C program that the `memmove()` routine is available to copy potentatially overlapping blocks of memory.

`d_memset`
  From d_memset.U:

  This variable conditionally defines the `HAS_MEMSET` symbol, which indicates to the C program that the `memset()` routine is available to set blocks of memory.

`d_mkdir`
  From d_mkdir.U:

  This variable conditionally defines the `HAS_MKDIR` symbol, which indicates to the C program that the `mkdir()` routine is available to create directories..

`d_mkdtemp`
  From d_mkdtemp.U:

  This variable conditionally defines the `HAS_MKDTEMP` symbol, which indicates to the C program that the `mkdtemp()` routine is available to exclusively create a uniquely named temporary directory.

`d_mkfifo`
  From d_mkfifo.U:

  This variable conditionally defines the `HAS_MKFIFO` symbol, which indicates to the C program that the `mkfifo()` routine is available.

`d_mkstemp`
  From d_mkstemp.U:

  This variable conditionally defines the `HAS_MKSTEMP` symbol, which indicates to the C program that the `mkstemp()` routine is available to exclusively create and open a uniquely named temporary file.

`d_mkstemps`
  From d_mkstemps.U:

  This variable conditionally defines the `HAS_MKSTEMPS` symbol, which indicates to the C program that the `mkstemps()` routine is available to exclusively create and open a uniquely named (with a suffix) temporary file.

`d_mktime`
  From d_mktime.U:

  This variable conditionally defines the `HAS_MKTIME` symbol, which indicates to the C program that the `mktime()` routine is available.

`d_mmap`
  From d_mmap.U:

  This variable conditionally defines `HAS_MMAP` if `mmap()` is available to map a file into memory.

`d_modfl`
  From d_modfl.U:

  This variable conditionally defines the `HAS_MODFL` symbol, which indicates to the C program that the `modfl()` routine is available.

`d_mprotect`
  From d_mprotect.U:

  This variable conditionally defines `HAS_MPROTECT` if `mprotect()` is available to modify the access protection of a memory mapped file.

`d_msg`
  From d_msg.U:

  This variable conditionally defines the `HAS_MSG` symbol, which indicates that the entire msg*(2) library is present.

`d_msg_ctrunc`
  From d_socket.U:

  This variable conditionally defines the `HAS_MSG_CTRUNC` symbol, which indicates that the `MSG_CTRUNC` is available. #ifdef is not enough because it may be an enum, glibc has been known to do this.

`d_msg_dontroute`
  From d_socket.U:

  This variable conditionally defines the `HAS_MSG_DONTROUTE` symbol, which indicates that the `MSG_DONTROUTE` is available. #ifdef is not enough because it may be an enum, glibc has been known to do this.

`d_msg_oob`
  From d_socket.U:

  This variable conditionally defines the `HAS_MSG_OOB` symbol, which indicates that the `MSG_OOB` is available. #ifdef is not enough because it may be an enum, glibc has been known to do this.

`d_msg_peek`
  From d_socket.U:

  This variable conditionally defines the `HAS_MSG_PEEK` symbol, which indicates that the `MSG_PEEK` is available. #ifdef is not enough because it may be an enum, glibc has been known to do this.

`d_msg_proxy`
  From d_socket.U:

  This variable conditionally defines the `HAS_MSG_PROXY` symbol, which indicates that the `MSG_PROXY` is available. #ifdef is not enough because it may be an enum, glibc has been known to do this.

`d_msgctl`
  From d_msgctl.U:

  This variable conditionally defines the `HAS_MSGCTL` symbol, which indicates to the C program that the `msgctl()` routine is available.

`d_msgget`
  From d_msgget.U:

  This variable conditionally defines the `HAS_MSGGET` symbol, which indicates to the C program that the `msgget()` routine is available.

`d_msgrcv`
  From d_msgrcv.U:

  This variable conditionally defines the `HAS_MSGRCV` symbol, which indicates to the C program that the `msgrcv()` routine is available.

`d_msgsnd`
  From d_msgsnd.U:

  This variable conditionally defines the `HAS_MSGSND` symbol, which indicates to the C program that the `msgsnd()` routine is available.

`d_msync`
  From d_msync.U:

  This variable conditionally defines `HAS_MSYNC` if `msync()` is available to synchronize a mapped file.

`d_munmap`
  From d_munmap.U:

  This variable conditionally defines `HAS_MUNMAP` if `munmap()` is available to unmap a region mapped by mmap().

`d_mymalloc`
  From mallocsrc.U:

  This variable conditionally defines `MYMALLOC` in case other parts of the source want to take special action if `MYMALLOC` is used. This may include different sorts of profiling or error detection.

`d_nice`
  From d_nice.U:

  This variable conditionally defines the `HAS_NICE` symbol, which indicates to the C program that the `nice()` routine is available.

`d_nv_preserves_uv`
  From perlxv.U:

  This variable indicates whether a variable of type nvtype can preserve all the bits a variable of type uvtype.

`d_nv_preserves_uv_bits`
  From perlxv.U:

  This variable indicates how many of bits type uvtype a variable nvtype can preserve.

`d_off64_t`
  From d_off64_t.U:

  This symbol will be defined if the C compiler supports off64_t.

`d_old_pthread_create_joinable`
  From d_pthrattrj.U:

  This variable conditionally defines pthread_create_joinable. undef if pthread.h defines `PTHREAD_CREATE_JOINABLE`.

`d_oldpthreads`
  From usethreads.U:

  This variable conditionally defines the `OLD_PTHREADS_API` symbol, and indicates that Perl should be built to use the old draft `POSIX` threads `API`. This is only potentially meaningful if usethreads is set.

`d_oldsock`
  From d_socket.U:

  This variable conditionally defines the `OLDSOCKET` symbol, which indicates that the `BSD` socket interface is based on 4.1c and not 4.2.

`d_open3`
  From d_open3.U:

  This variable conditionally defines the HAS_OPEN3 manifest constant, which indicates to the C program that the 3 argument version of the `open(2)` function is available.

`d_pathconf`
  From d_pathconf.U:

  This variable conditionally defines the `HAS_PATHCONF` symbol, which indicates to the C program that the `pathconf()` routine is available to determine file-system related limits and options associated with a given filename.

`d_pause`
  From d_pause.U:

  This variable conditionally defines the `HAS_PAUSE` symbol, which indicates to the C program that the `pause()` routine is available to suspend a process until a signal is received.

`d_perl_otherlibdirs`
  From otherlibdirs.U:

  This variable conditionally defines `PERL_OTHERLIBDIRS`, which contains a colon-separated set of paths for the perl binary to include in @`INC`. See also otherlibdirs.

`d_phostname`
  From d_gethname.U:

  This variable conditionally defines the `HAS_PHOSTNAME` symbol, which contains the shell command which, when fed to popen(), may be used to derive the host name.

`d_pipe`
  From d_pipe.U:

  This variable conditionally defines the `HAS_PIPE` symbol, which indicates to the C program that the `pipe()` routine is available to create an inter-process channel.

`d_poll`
  From d_poll.U:

  This variable conditionally defines the `HAS_POLL` symbol, which indicates to the C program that the `poll()` routine is available to poll active file descriptors.

`d_portable`
  From d_portable.U:

  This variable conditionally defines the `PORTABLE` symbol, which indicates to the C program that it should not assume that it is running on the machine it was compiled on.

`d_PRId64`
  From quadfio.U:

  This variable conditionally defines the PERL_PRId64 symbol, which indiciates that stdio has a symbol to print 64-bit decimal numbers.

`d_PRIeldbl`
  From longdblfio.U:

  This variable conditionally defines the PERL_PRIfldbl symbol, which indiciates that stdio has a symbol to print long doubles.

`d_PRIEUldbl`
  From longdblfio.U:

  This variable conditionally defines the PERL_PRIfldbl symbol, which indiciates that stdio has a symbol to print long doubles. The `U` in the name is to separate this from d_PRIeldbl so that even case-blind systems can see the difference.

`d_PRIfldbl`
  From longdblfio.U:

  This variable conditionally defines the PERL_PRIfldbl symbol, which indiciates that stdio has a symbol to print long doubles.

`d_PRIFUldbl`
  From longdblfio.U:

  This variable conditionally defines the PERL_PRIfldbl symbol, which indiciates that stdio has a symbol to print long doubles. The `U` in the name is to separate this from d_PRIfldbl so that even case-blind systems can see the difference.

`d_PRIgldbl`
  From longdblfio.U:

  This variable conditionally defines the PERL_PRIfldbl symbol, which indiciates that stdio has a symbol to print long doubles.

`d_PRIGUldbl`
  From longdblfio.U:

  This variable conditionally defines the PERL_PRIfldbl symbol, which indiciates that stdio has a symbol to print long doubles. The `U` in the name is to separate this from d_PRIgldbl so that even case-blind systems can see the difference.

`d_PRIi64`
  From quadfio.U:

  This variable conditionally defines the PERL_PRIi64 symbol, which indiciates that stdio has a symbol to print 64-bit decimal numbers.

`d_PRIo64`
  From quadfio.U:

  This variable conditionally defines the PERL_PRIo64 symbol, which indiciates that stdio has a symbol to print 64-bit octal numbers.

`d_PRIu64`
  From quadfio.U:

  This variable conditionally defines the PERL_PRIu64 symbol, which indiciates that stdio has a symbol to print 64-bit unsigned decimal numbers.

`d_PRIx64`
  From quadfio.U:

  This variable conditionally defines the PERL_PRIx64 symbol, which indiciates that stdio has a symbol to print 64-bit hexadecimal numbers.

`d_PRIXU64`
  From quadfio.U:

  This variable conditionally defines the PERL_PRIXU64 symbol, which indiciates that stdio has a symbol to print 64-bit hExADECimAl numbers. The `U` in the name is to separate this from d_PRIx64 so that even case-blind systems can see the difference.

`d_pthread_atfork`
  From d_pthread_atfork.U:

  This variable conditionally defines the `HAS_PTHREAD_ATFORK` symbol, which indicates to the C program that the `pthread_atfork()` routine is available.

`d_pthread_yield`
  From d_pthread_y.U:

  This variable conditionally defines the `HAS_PTHREAD_YIELD` symbol if the pthread_yield routine is available to yield the execution of the current thread.

`d_pwage`
  From i_pwd.U:

  This variable conditionally defines `PWAGE`, which indicates that struct passwd contains pw_age.

`d_pwchange`
  From i_pwd.U:

  This variable conditionally defines `PWCHANGE`, which indicates that struct passwd contains pw_change.

`d_pwclass`
  From i_pwd.U:

  This variable conditionally defines `PWCLASS`, which indicates that struct passwd contains pw_class.

`d_pwcomment`
  From i_pwd.U:

  This variable conditionally defines `PWCOMMENT`, which indicates that struct passwd contains pw_comment.

`d_pwexpire`
  From i_pwd.U:

  This variable conditionally defines `PWEXPIRE`, which indicates that struct passwd contains pw_expire.

`d_pwgecos`
  From i_pwd.U:

  This variable conditionally defines `PWGECOS`, which indicates that struct passwd contains pw_gecos.

`d_pwpasswd`
  From i_pwd.U:

  This variable conditionally defines `PWPASSWD`, which indicates that struct passwd contains pw_passwd.

`d_pwquota`
  From i_pwd.U:

  This variable conditionally defines `PWQUOTA`, which indicates that struct passwd contains pw_quota.

`d_qgcvt`
  From d_qgcvt.U:

  This variable conditionally defines the `HAS_QGCVT` symbol, which indicates to the C program that the `qgcvt()` routine is available.

`d_quad`
  From quadtype.U:

  This variable, if defined, tells that there's a 64-bit integer type, quadtype.

`d_readdir`
  From d_readdir.U:

  This variable conditionally defines `HAS_READDIR` if `readdir()` is available to read directory entries.

`d_readlink`
  From d_readlink.U:

  This variable conditionally defines the `HAS_READLINK` symbol, which indicates to the C program that the `readlink()` routine is available to read the value of a symbolic link.

`d_rename`
  From d_rename.U:

  This variable conditionally defines the `HAS_RENAME` symbol, which indicates to the C program that the `rename()` routine is available to rename files.

`d_rewinddir`
  From d_readdir.U:

  This variable conditionally defines `HAS_REWINDDIR` if `rewinddir()` is available.

`d_rmdir`
  From d_rmdir.U:

  This variable conditionally defines `HAS_RMDIR` if `rmdir()` is available to remove directories.

`d_safebcpy`
  From d_safebcpy.U:

  This variable conditionally defines the `HAS_SAFE_BCOPY` symbol if the `bcopy()` routine can do overlapping copies.

`d_safemcpy`
  From d_safemcpy.U:

  This variable conditionally defines the `HAS_SAFE_MEMCPY` symbol if the `memcpy()` routine can do overlapping copies.

`d_sanemcmp`
  From d_sanemcmp.U:

  This variable conditionally defines the `HAS_SANE_MEMCMP` symbol if the `memcpy()` routine is available and can be used to compare relative magnitudes of chars with their high bits set.

`d_sbrkproto`
  From d_sbrkproto.U:

  This variable conditionally defines the `HAS_SBRK_PROTO` symbol, which indicates to the C program that the system provides a prototype for the `sbrk()` function. Otherwise, it is up to the program to supply one.

`d_sched_yield`
  From d_pthread_y.U:

  This variable conditionally defines the `HAS_SCHED_YIELD` symbol if the sched_yield routine is available to yield the execution of the current thread.

`d_scm_rights`
  From d_socket.U:

  This variable conditionally defines the `HAS_SCM_RIGHTS` symbol, which indicates that the `SCM_RIGHTS` is available. #ifdef is not enough because it may be an enum, glibc has been known to do this.

`d_SCNfldbl`
  From longdblfio.U:

  This variable conditionally defines the PERL_PRIfldbl symbol, which indiciates that stdio has a symbol to scan long doubles.

`d_seekdir`
  From d_readdir.U:

  This variable conditionally defines `HAS_SEEKDIR` if `seekdir()` is available.

`d_select`
  From d_select.U:

  This variable conditionally defines `HAS_SELECT` if `select()` is available to select active file descriptors. A <sys/time.h> inclusion may be necessary for the timeout field.

`d_sem`
  From d_sem.U:

  This variable conditionally defines the `HAS_SEM` symbol, which indicates that the entire sem*(2) library is present.

`d_semctl`
  From d_semctl.U:

  This variable conditionally defines the `HAS_SEMCTL` symbol, which indicates to the C program that the `semctl()` routine is available.

`d_semctl_semid_ds`
  From d_union_semun.U:

  This variable conditionally defines `USE_SEMCTL_SEMID_DS`, which indicates that struct semid_ds * is to be used for semctl `IPC_STAT`.

`d_semctl_semun`
  From d_union_semun.U:

  This variable conditionally defines `USE_SEMCTL_SEMUN`, which indicates that union semun is to be used for semctl `IPC_STAT`.

`d_semget`
  From d_semget.U:

  This variable conditionally defines the `HAS_SEMGET` symbol, which indicates to the C program that the `semget()` routine is available.

`d_semop`
  From d_semop.U:

  This variable conditionally defines the `HAS_SEMOP` symbol, which indicates to the C program that the `semop()` routine is available.

`d_setegid`
  From d_setegid.U:

  This variable conditionally defines the `HAS_SETEGID` symbol, which indicates to the C program that the `setegid()` routine is available to change the effective gid of the current program.

`d_seteuid`
  From d_seteuid.U:

  This variable conditionally defines the `HAS_SETEUID` symbol, which indicates to the C program that the `seteuid()` routine is available to change the effective uid of the current program.

`d_setgrent`
  From d_setgrent.U:

  This variable conditionally defines the `HAS_SETGRENT` symbol, which indicates to the C program that the `setgrent()` routine is available for initializing sequential access to the group database.

`d_setgrps`
  From d_setgrps.U:

  This variable conditionally defines the `HAS_SETGROUPS` symbol, which indicates to the C program that the `setgroups()` routine is available to set the list of process groups.

`d_sethent`
  From d_sethent.U:

  This variable conditionally defines `HAS_SETHOSTENT` if `sethostent()` is available.

`d_setlinebuf`
  From d_setlnbuf.U:

  This variable conditionally defines the `HAS_SETLINEBUF` symbol, which indicates to the C program that the `setlinebuf()` routine is available to change stderr or stdout from block-buffered or unbuffered to a line-buffered mode.

`d_setlocale`
  From d_setlocale.U:

  This variable conditionally defines `HAS_SETLOCALE` if `setlocale()` is available to handle locale-specific ctype implementations.

`d_setnent`
  From d_setnent.U:

  This variable conditionally defines `HAS_SETNETENT` if `setnetent()` is available.

`d_setpent`
  From d_setpent.U:

  This variable conditionally defines `HAS_SETPROTOENT` if `setprotoent()` is available.

`d_setpgid`
  From d_setpgid.U:

  This variable conditionally defines the `HAS_SETPGID` symbol if the setpgid(pid, gpid) function is available to set process group `ID`.

`d_setpgrp2`
  From d_setpgrp2.U:

  This variable conditionally defines the HAS_SETPGRP2 symbol, which indicates to the C program that the `setpgrp2()` (as in DG/`UX`) routine is available to set the current process group.

`d_setpgrp`
  From d_setpgrp.U:

  This variable conditionally defines `HAS_SETPGRP` if `setpgrp()` is available to set the current process group.

`d_setprior`
  From d_setprior.U:

  This variable conditionally defines `HAS_SETPRIORITY` if `setpriority()` is available to set a process's priority.

`d_setproctitle`
  From d_setproctitle.U:

  This variable conditionally defines the `HAS_SETPROCTITLE` symbol, which indicates to the C program that the `setproctitle()` routine is available.

`d_setpwent`
  From d_setpwent.U:

  This variable conditionally defines the `HAS_SETPWENT` symbol, which indicates to the C program that the `setpwent()` routine is available for initializing sequential access to the passwd database.

`d_setregid`
  From d_setregid.U:

  This variable conditionally defines `HAS_SETREGID` if `setregid()` is available to change the real and effective gid of the current process.

`d_setresgid`
  From d_setregid.U:

  This variable conditionally defines `HAS_SETRESGID` if `setresgid()` is available to change the real, effective and saved gid of the current process.

`d_setresuid`
  From d_setreuid.U:

  This variable conditionally defines `HAS_SETREUID` if `setresuid()` is available to change the real, effective and saved uid of the current process.

`d_setreuid`
  From d_setreuid.U:

  This variable conditionally defines `HAS_SETREUID` if `setreuid()` is available to change the real and effective uid of the current process.

`d_setrgid`
  From d_setrgid.U:

  This variable conditionally defines the `HAS_SETRGID` symbol, which indicates to the C program that the `setrgid()` routine is available to change the real gid of the current program.

`d_setruid`
  From d_setruid.U:

  This variable conditionally defines the `HAS_SETRUID` symbol, which indicates to the C program that the `setruid()` routine is available to change the real uid of the current program.

`d_setsent`
  From d_setsent.U:

  This variable conditionally defines `HAS_SETSERVENT` if `setservent()` is available.

`d_setsid`
  From d_setsid.U:

  This variable conditionally defines `HAS_SETSID` if `setsid()` is available to set the process group `ID`.

`d_setvbuf`
  From d_setvbuf.U:

  This variable conditionally defines the `HAS_SETVBUF` symbol, which indicates to the C program that the `setvbuf()` routine is available to change buffering on an open stdio stream.

`d_sfio`
  From d_sfio.U:

  This variable conditionally defines the `USE_SFIO` symbol, and indicates whether sfio is available (and should be used).

`d_shm`
  From d_shm.U:

  This variable conditionally defines the `HAS_SHM` symbol, which indicates that the entire shm*(2) library is present.

`d_shmat`
  From d_shmat.U:

  This variable conditionally defines the `HAS_SHMAT` symbol, which indicates to the C program that the `shmat()` routine is available.

`d_shmatprototype`
  From d_shmat.U:

  This variable conditionally defines the `HAS_SHMAT_PROTOTYPE` symbol, which indicates that sys/shm.h has a prototype for shmat.

`d_shmctl`
  From d_shmctl.U:

  This variable conditionally defines the `HAS_SHMCTL` symbol, which indicates to the C program that the `shmctl()` routine is available.

`d_shmdt`
  From d_shmdt.U:

  This variable conditionally defines the `HAS_SHMDT` symbol, which indicates to the C program that the `shmdt()` routine is available.

`d_shmget`
  From d_shmget.U:

  This variable conditionally defines the `HAS_SHMGET` symbol, which indicates to the C program that the `shmget()` routine is available.

`d_sigaction`
  From d_sigaction.U:

  This variable conditionally defines the `HAS_SIGACTION` symbol, which indicates that the Vr4 `sigaction()` routine is available.

`d_sigprocmask`
  From d_sigprocmask.U:

  This variable conditionally defines `HAS_SIGPROCMASK` if `sigprocmask()` is available to examine or change the signal mask of the calling process.

`d_sigsetjmp`
  From d_sigsetjmp.U:

  This variable conditionally defines the `HAS_SIGSETJMP` symbol, which indicates that the `sigsetjmp()` routine is available to call `setjmp()` and optionally save the process's signal mask.

`d_socket`
  From d_socket.U:

  This variable conditionally defines `HAS_SOCKET`, which indicates that the `BSD` socket interface is supported.

`d_socklen_t`
  From d_socklen_t.U:

  This symbol will be defined if the C compiler supports socklen_t.

`d_sockpair`
  From d_socket.U:

  This variable conditionally defines the `HAS_SOCKETPAIR` symbol, which indicates that the `BSD` `socketpair()` is supported.

`d_socks5_init`
  From d_socks5_init.U:

  This variable conditionally defines the HAS_SOCKS5_INIT symbol, which indicates to the C program that the `socks5_init()` routine is available.

`d_sqrtl`
  From d_sqrtl.U:

  This variable conditionally defines the `HAS_SQRTL` symbol, which indicates to the C program that the `sqrtl()` routine is available.

`d_statblks`
  From d_statblks.U:

  This variable conditionally defines `USE_STAT_BLOCKS` if this system has a stat structure declaring st_blksize and st_blocks.

`d_statfs_f_flags`
  From d_statfs_f_flags.U:

  This variable conditionally defines the `HAS_STRUCT_STATFS_F_FLAGS` symbol, which indicates to struct statfs from has f_flags member. This kind of struct statfs is coming from sys/mount.h (`BSD`), not from sys/statfs.h (`SYSV`).

`d_statfs_s`
  From d_statfs_s.U:

  This variable conditionally defines the `HAS_STRUCT_STATFS` symbol, which indicates that the struct statfs is supported.

`d_statvfs`
  From d_statvfs.U:

  This variable conditionally defines the `HAS_STATVFS` symbol, which indicates to the C program that the `statvfs()` routine is available.

`d_stdio_cnt_lval`
  From d_stdstdio.U:

  This variable conditionally defines `STDIO_CNT_LVALUE` if the `FILE_cnt` macro can be used as an lvalue.

`d_stdio_ptr_lval`
  From d_stdstdio.U:

  This variable conditionally defines `STDIO_PTR_LVALUE` if the `FILE_ptr` macro can be used as an lvalue.

`d_stdio_ptr_lval_nochange_cnt`
  From d_stdstdio.U:

  This symbol is defined if using the `FILE_ptr` macro as an lvalue to increase the pointer by n leaves `File_cnt(fp)` unchanged.

`d_stdio_ptr_lval_sets_cnt`
  From d_stdstdio.U:

  This symbol is defined if using the `FILE_ptr` macro as an lvalue to increase the pointer by n has the side effect of decreasing the value of `File_cnt(fp)` by n.

`d_stdio_stream_array`
  From stdio_streams.U:

  This variable tells whether there is an array holding the stdio streams.

`d_stdiobase`
  From d_stdstdio.U:

  This variable conditionally defines `USE_STDIO_BASE` if this system has a `FILE` structure declaring a usable _base field (or equivalent) in stdio.h.

`d_stdstdio`
  From d_stdstdio.U:

  This variable conditionally defines `USE_STDIO_PTR` if this system has a `FILE` structure declaring usable _ptr and _cnt fields (or equivalent) in stdio.h.

`d_strchr`
  From d_strchr.U:

  This variable conditionally defines `HAS_STRCHR` if `strchr()` and `strrchr()` are available for string searching.

`d_strcoll`
  From d_strcoll.U:

  This variable conditionally defines `HAS_STRCOLL` if `strcoll()` is available to compare strings using collating information.

`d_strctcpy`
  From d_strctcpy.U:

  This variable conditionally defines the `USE_STRUCT_COPY` symbol, which indicates to the C program that this C compiler knows how to copy structures.

`d_strerrm`
  From d_strerror.U:

  This variable holds what Strerrr is defined as to translate an error code condition into an error message string. It could be `strerror` or a more `complex` macro emulating strrror with sys_errlist[], or the `unknown` string when both strerror and sys_errlist are missing.

`d_strerror`
  From d_strerror.U:

  This variable conditionally defines `HAS_STRERROR` if `strerror()` is available to translate error numbers to strings.

`d_strtod`
  From d_strtod.U:

  This variable conditionally defines the `HAS_STRTOD` symbol, which indicates to the C program that the `strtod()` routine is available to provide better numeric string conversion than atof().

`d_strtol`
  From d_strtol.U:

  This variable conditionally defines the `HAS_STRTOL` symbol, which indicates to the C program that the `strtol()` routine is available to provide better numeric string conversion than `atoi()` and friends.

`d_strtold`
  From d_strtold.U:

  This variable conditionally defines the `HAS_STRTOLD` symbol, which indicates to the C program that the `strtold()` routine is available.

`d_strtoll`
  From d_strtoll.U:

  This variable conditionally defines the `HAS_STRTOLL` symbol, which indicates to the C program that the `strtoll()` routine is available.

`d_strtoq`
  From d_strtoq.U:

  This variable conditionally defines the `HAS_STRTOQ` symbol, which indicates to the C program that the `strtoq()` routine is available.

`d_strtoul`
  From d_strtoul.U:

  This variable conditionally defines the `HAS_STRTOUL` symbol, which indicates to the C program that the `strtoul()` routine is available to provide conversion of strings to unsigned long.

`d_strtoull`
  From d_strtoull.U:

  This variable conditionally defines the `HAS_STRTOULL` symbol, which indicates to the C program that the `strtoull()` routine is available.

`d_strtouq`
  From d_strtouq.U:

  This variable conditionally defines the `HAS_STRTOUQ` symbol, which indicates to the C program that the `strtouq()` routine is available.

`d_strxfrm`
  From d_strxfrm.U:

  This variable conditionally defines `HAS_STRXFRM` if `strxfrm()` is available to transform strings.

`d_suidsafe`
  From d_dosuid.U:

  This variable conditionally defines `SETUID_SCRIPTS_ARE_SECURE_NOW` if setuid scripts can be secure. This test looks in /dev/fd/.

`d_symlink`
  From d_symlink.U:

  This variable conditionally defines the `HAS_SYMLINK` symbol, which indicates to the C program that the `symlink()` routine is available to create symbolic links.

`d_syscall`
  From d_syscall.U:

  This variable conditionally defines `HAS_SYSCALL` if `syscall()` is available call arbitrary system calls.

`d_sysconf`
  From d_sysconf.U:

  This variable conditionally defines the `HAS_SYSCONF` symbol, which indicates to the C program that the `sysconf()` routine is available to determine system related limits and options.

`d_sysernlst`
  From d_strerror.U:

  This variable conditionally defines `HAS_SYS_ERRNOLIST` if sys_errnolist[] is available to translate error numbers to the symbolic name.

`d_syserrlst`
  From d_strerror.U:

  This variable conditionally defines `HAS_SYS_ERRLIST` if sys_errlist[] is available to translate error numbers to strings.

`d_system`
  From d_system.U:

  This variable conditionally defines `HAS_SYSTEM` if `system()` is available to issue a shell command.

`d_tcgetpgrp`
  From d_tcgtpgrp.U:

  This variable conditionally defines the `HAS_TCGETPGRP` symbol, which indicates to the C program that the `tcgetpgrp()` routine is available. to get foreground process group `ID`.

`d_tcsetpgrp`
  From d_tcstpgrp.U:

  This variable conditionally defines the `HAS_TCSETPGRP` symbol, which indicates to the C program that the `tcsetpgrp()` routine is available to set foreground process group `ID`.

`d_telldir`
  From d_readdir.U:

  This variable conditionally defines `HAS_TELLDIR` if `telldir()` is available.

`d_telldirproto`
  From d_telldirproto.U:

  This variable conditionally defines the `HAS_TELLDIR_PROTO` symbol, which indicates to the C program that the system provides a prototype for the `telldir()` function. Otherwise, it is up to the program to supply one.

`d_time`
  From d_time.U:

  This variable conditionally defines the `HAS_TIME` symbol, which indicates that the `time()` routine exists. The `time()` routine is normaly provided on `UNIX` systems.

`d_times`
  From d_times.U:

  This variable conditionally defines the `HAS_TIMES` symbol, which indicates that the `times()` routine exists. The `times()` routine is normaly provided on `UNIX` systems. You may have to include <sys/times.h>.

`d_truncate`
  From d_truncate.U:

  This variable conditionally defines `HAS_TRUNCATE` if `truncate()` is available to truncate files.

`d_tzname`
  From d_tzname.U:

  This variable conditionally defines `HAS_TZNAME` if tzname[] is available to access timezone names.

`d_umask`
  From d_umask.U:

  This variable conditionally defines the `HAS_UMASK` symbol, which indicates to the C program that the `umask()` routine is available. to set and get the value of the file creation mask.

`d_uname`
  From d_gethname.U:

  This variable conditionally defines the `HAS_UNAME` symbol, which indicates to the C program that the `uname()` routine may be used to derive the host name.

`d_union_semun`
  From d_union_semun.U:

  This variable conditionally defines `HAS_UNION_SEMUN` if the union semun is defined by including <sys/sem.h>.

`d_ustat`
  From d_ustat.U:

  This variable conditionally defines `HAS_USTAT` if `ustat()` is available to query file system statistics by dev_t.

`d_vendorarch`
  From vendorarch.U:

  This variable conditionally defined `PERL_VENDORARCH`.

`d_vendorbin`
  From vendorbin.U:

  This variable conditionally defines `PERL_VENDORBIN`.

`d_vendorlib`
  From vendorlib.U:

  This variable conditionally defines `PERL_VENDORLIB`.

`d_vfork`
  From d_vfork.U:

  This variable conditionally defines the `HAS_VFORK` symbol, which indicates the `vfork()` routine is available.

`d_void_closedir`
  From d_closedir.U:

  This variable conditionally defines `VOID_CLOSEDIR` if `closedir()` does not return a value.

`d_voidsig`
  From d_voidsig.U:

  This variable conditionally defines `VOIDSIG` if this system declares ``void (*signal(...))()'' in signal.h. The old way was to declare it as ``int (*signal(...))()''.

`d_voidtty`
  From i_sysioctl.U:

  This variable conditionally defines `USE_IOCNOTTY` to indicate that the `ioctl()` call with `TIOCNOTTY` should be used to void tty association. Otherwise (on `USG` probably), it is enough to close the standard file decriptors and do a setpgrp().

`d_volatile`
  From d_volatile.U:

  This variable conditionally defines the `HASVOLATILE` symbol, which indicates to the C program that this C compiler knows about the volatile declaration.

`d_vprintf`
  From d_vprintf.U:

  This variable conditionally defines the `HAS_VPRINTF` symbol, which indicates to the C program that the `vprintf()` routine is available to printf with a pointer to an argument list.

`d_wait4`
  From d_wait4.U:

  This variable conditionally defines the HAS_WAIT4 symbol, which indicates the `wait4()` routine is available.

`d_waitpid`
  From d_waitpid.U:

  This variable conditionally defines `HAS_WAITPID` if `waitpid()` is available to wait for child process.

`d_wcstombs`
  From d_wcstombs.U:

  This variable conditionally defines the `HAS_WCSTOMBS` symbol, which indicates to the C program that the `wcstombs()` routine is available to convert wide character strings to multibyte strings.

`d_wctomb`
  From d_wctomb.U:

  This variable conditionally defines the `HAS_WCTOMB` symbol, which indicates to the C program that the `wctomb()` routine is available to convert a wide character to a multibyte.

`d_xenix`
  From Guess.U:

  This variable conditionally defines the symbol `XENIX`, which alerts the C program that it runs under Xenix.

`date`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the date program. After Configure runs, the value is reset to a plain `date` and is not useful.

`db_hashtype`
  From i_db.U:

  This variable contains the type of the hash structure element in the <db.h> header file. In older versions of `DB`, it was int, while in newer ones it is u_int32_t.

`db_prefixtype`
  From i_db.U:

  This variable contains the type of the prefix structure element in the <db.h> header file. In older versions of `DB`, it was int, while in newer ones it is size_t.

`defvoidused`
  From voidflags.U:

  This variable contains the default value of the `VOIDUSED` symbol (15).

`direntrytype`
  From i_dirent.U:

  This symbol is set to `struct direct` or `struct dirent` depending on whether dirent is available or not. You should use this pseudo type to portably declare your directory entries.

`dlext`
  From dlext.U:

  This variable contains the extension that is to be used for the dynamically loaded modules that perl generaties.

`dlsrc`
  From dlsrc.U:

  This variable contains the name of the dynamic loading file that will be used with the package.

`doublesize`
  From doublesize.U:

  This variable contains the value of the `DOUBLESIZE` symbol, which indicates to the C program how many bytes there are in a double.

`drand01`
  From randfunc.U:

  Indicates the macro to be used to generate normalized random numbers. Uses randfunc, often divided by (double) (((unsigned long) 1 << randbits)) in order to normalize the result. In C programs, the macro `Drand01` is mapped to drand01.

`dynamic_ext`
  From Extensions.U:

  This variable holds a list of `XS` extension files we want to link dynamically into the package. It is used by Makefile.

## e

`eagain`
  From nblock_io.U:

  This variable bears the symbolic errno code set by `read()` when no data is present on the file and non-blocking I/O was enabled (otherwise, `read()` blocks naturally).

`ebcdic`
  From ebcdic.U:

  This variable conditionally defines `EBCDIC` if this system uses `EBCDIC` encoding. Among other things, this means that the character ranges are not contiguous. See trnl.U

`echo`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the echo program. After Configure runs, the value is reset to a plain `echo` and is not useful.

`egrep`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the egrep program. After Configure runs, the value is reset to a plain `egrep` and is not useful.

`emacs`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`eunicefix`
  From Init.U:

  When running under Eunice this variable contains a command which will convert a shell script to the proper form of text file for it to be executable by the shell. On other systems it is a no-op.

`exe_ext`
  From Unix.U:

  This is an old synonym for _exe.

`expr`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the expr program. After Configure runs, the value is reset to a plain `expr` and is not useful.

`extensions`
  From Extensions.U:

  This variable holds a list of all extension files (both `XS` and non-xs linked into the package. It is propagated to Config.pm and is typically used to test whether a particular extesion is available.

## f

`fflushall`
  From fflushall.U:

  This symbol, if defined, tells that to flush all pending stdio output one must loop through all the stdio file handles stored in an array and fflush them. Note that if fflushNULL is defined, fflushall will not even be probed for and will be left undefined.

`fflushNULL`
  From fflushall.U:

  This symbol, if defined, tells that fflush(`NULL`) does flush all pending stdio output.

`find`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`firstmakefile`
  From Unix.U:

  This variable defines the first file searched by make. On unix, it is makefile (then Makefile). On case-insensitive systems, it might be something else. This is only used to deal with convoluted make depend tricks.

`flex`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`fpossize`
  From fpossize.U:

  This variable contains the size of a fpostype in bytes.

`fpostype`
  From fpostype.U:

  This variable defines Fpos_t to be something like fpos_t, long, uint, or whatever type is used to declare file positions in libc.

`freetype`
  From mallocsrc.U:

  This variable contains the return type of free(). It is usually void, but occasionally int.

`full_ar`
  From Loc_ar.U:

  This variable contains the full pathname to `ar`, whether or not the user has specified `portability`. This is only used in the Makefile.SH.

`full_csh`
  From d_csh.U:

  This variable contains the full pathname to `csh`, whether or not the user has specified `portability`. This is only used in the compiled C program, and we assume that all systems which can share this executable will have the same full pathname to csh.

`full_sed`
  From Loc_sed.U:

  This variable contains the full pathname to `sed`, whether or not the user has specified `portability`. This is only used in the compiled C program, and we assume that all systems which can share this executable will have the same full pathname to sed.

## g

`gccosandvers`
  From gccvers.U:

  If `GNU` cc (gcc) is used, this variable the operating system and version used to compile the gcc. It is set to '' if not gcc, or if nothing useful can be parsed as the os version.

`gccversion`
  From gccvers.U:

  If `GNU` cc (gcc) is used, this variable holds `1` or `2` to indicate whether the compiler is version 1 or 2. This is used in setting some of the default cflags. It is set to '' if not gcc.

`gidformat`
  From gidf.U:

  This variable contains the format string used for printing a Gid_t.

`gidsign`
  From gidsign.U:

  This variable contains the signedness of a gidtype. 1 for unsigned, -1 for signed.

`gidsize`
  From gidsize.U:

  This variable contains the size of a gidtype in bytes.

`gidtype`
  From gidtype.U:

  This variable defines Gid_t to be something like gid_t, int, ushort, or whatever type is used to declare the return type of getgid(). Typically, it is the type of group ids in the kernel.

`glibpth`
  From libpth.U:

  This variable holds the general path (space-separated) used to find libraries. It may contain directories that do not exist on this platform, libpth is the cleaned-up version.

`grep`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the grep program. After Configure runs, the value is reset to a plain `grep` and is not useful.

`groupcat`
  From nis.U:

  This variable contains a command that produces the text of the /etc/group file. This is normally ``cat /etc/group'', but can be ``ypcat group'' when `NIS` is used. On some systems, such as os390, there may be no equivalent command, in which case this variable is unset.

`groupstype`
  From groupstype.U:

  This variable defines Groups_t to be something like gid_t, int, ushort, or whatever type is used for the second argument to `getgroups()` and setgroups(). Usually, this is the same as gidtype (gid_t), but sometimes it isn't.

`gzip`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the gzip program. After Configure runs, the value is reset to a plain `gzip` and is not useful.

## h

`h_fcntl`
  From h_fcntl.U:

  This is variable gets set in various places to tell i_fcntl that <fcntl.h> should be included.

`h_sysfile`
  From h_sysfile.U:

  This is variable gets set in various places to tell i_sys_file that <sys/file.h> should be included.

`hint`
  From Oldconfig.U:

  Gives the type of hints used for previous answers. May be one of `default`, `recommended` or `previous`.

`hostcat`
  From nis.U:

  This variable contains a command that produces the text of the /etc/hosts file. This is normally ``cat /etc/hosts'', but can be ``ypcat hosts'' when `NIS` is used. On some systems, such as os390, there may be no equivalent command, in which case this variable is unset.

## i

`i16size`
  From perlxv.U:

  This variable is the size of an I16 in bytes.

`i16type`
  From perlxv.U:

  This variable contains the C type used for Perl's I16.

`i32size`
  From perlxv.U:

  This variable is the size of an I32 in bytes.

`i32type`
  From perlxv.U:

  This variable contains the C type used for Perl's I32.

`i64size`
  From perlxv.U:

  This variable is the size of an I64 in bytes.

`i64type`
  From perlxv.U:

  This variable contains the C type used for Perl's I64.

`i8size`
  From perlxv.U:

  This variable is the size of an I8 in bytes.

`i8type`
  From perlxv.U:

  This variable contains the C type used for Perl's I8.

`i_arpainet`
  From i_arpainet.U:

  This variable conditionally defines the `I_ARPA_INET` symbol, and indicates whether a C program should include <arpa/inet.h>.

`i_bsdioctl`
  From i_sysioctl.U:

  This variable conditionally defines the `I_SYS_BSDIOCTL` symbol, which indicates to the C program that <sys/bsdioctl.h> exists and should be included.

`i_db`
  From i_db.U:

  This variable conditionally defines the `I_DB` symbol, and indicates whether a C program may include Berkeley's `DB` include file <db.h>.

`i_dbm`
  From i_dbm.U:

  This variable conditionally defines the `I_DBM` symbol, which indicates to the C program that <dbm.h> exists and should be included.

`i_dirent`
  From i_dirent.U:

  This variable conditionally defines `I_DIRENT`, which indicates to the C program that it should include <dirent.h>.

`i_dld`
  From i_dld.U:

  This variable conditionally defines the `I_DLD` symbol, which indicates to the C program that <dld.h> (`GNU` dynamic loading) exists and should be included.

`i_dlfcn`
  From i_dlfcn.U:

  This variable conditionally defines the `I_DLFCN` symbol, which indicates to the C program that <dlfcn.h> exists and should be included.

`i_fcntl`
  From i_fcntl.U:

  This variable controls the value of `I_FCNTL` (which tells the C program to include <fcntl.h>).

`i_float`
  From i_float.U:

  This variable conditionally defines the `I_FLOAT` symbol, and indicates whether a C program may include <float.h> to get symbols like `DBL_MAX` or `DBL_MIN`, i.e. machine dependent floating point values.

`i_gdbm`
  From i_gdbm.U:

  This variable conditionally defines the `I_GDBM` symbol, which indicates to the C program that <gdbm.h> exists and should be included.

`i_grp`
  From i_grp.U:

  This variable conditionally defines the `I_GRP` symbol, and indicates whether a C program should include <grp.h>.

`i_iconv`
  From i_iconv.U:

  This variable conditionally defines the `I_ICONV` symbol, and indicates whether a C program should include <iconv.h>.

`i_ieeefp`
  From i_ieeefp.U:

  This variable conditionally defines the `I_IEEEFP` symbol, and indicates whether a C program should include <ieeefp.h>.

`i_inttypes`
  From i_inttypes.U:

  This variable conditionally defines the `I_INTTYPES` symbol, and indicates whether a C program should include <inttypes.h>.

`i_libutil`
  From i_libutil.U:

  This variable conditionally defines the `I_LIBUTIL` symbol, and indicates whether a C program should include <libutil.h>.

`i_limits`
  From i_limits.U:

  This variable conditionally defines the `I_LIMITS` symbol, and indicates whether a C program may include <limits.h> to get symbols like `WORD_BIT` and friends.

`i_locale`
  From i_locale.U:

  This variable conditionally defines the `I_LOCALE` symbol, and indicates whether a C program should include <locale.h>.

`i_machcthr`
  From i_machcthr.U:

  This variable conditionally defines the `I_MACH_CTHREADS` symbol, and indicates whether a C program should include <mach/cthreads.h>.

`i_malloc`
  From i_malloc.U:

  This variable conditionally defines the `I_MALLOC` symbol, and indicates whether a C program should include <malloc.h>.

`i_math`
  From i_math.U:

  This variable conditionally defines the `I_MATH` symbol, and indicates whether a C program may include <math.h>.

`i_memory`
  From i_memory.U:

  This variable conditionally defines the `I_MEMORY` symbol, and indicates whether a C program should include <memory.h>.

`i_mntent`
  From i_mntent.U:

  This variable conditionally defines the `I_MNTENT` symbol, and indicates whether a C program should include <mntent.h>.

`i_ndbm`
  From i_ndbm.U:

  This variable conditionally defines the `I_NDBM` symbol, which indicates to the C program that <ndbm.h> exists and should be included.

`i_netdb`
  From i_netdb.U:

  This variable conditionally defines the `I_NETDB` symbol, and indicates whether a C program should include <netdb.h>.

`i_neterrno`
  From i_neterrno.U:

  This variable conditionally defines the `I_NET_ERRNO` symbol, which indicates to the C program that <net/errno.h> exists and should be included.

`i_netinettcp`
  From i_netinettcp.U:

  This variable conditionally defines the `I_NETINET_TCP` symbol, and indicates whether a C program should include <netinet/tcp.h>.

`i_niin`
  From i_niin.U:

  This variable conditionally defines `I_NETINET_IN`, which indicates to the C program that it should include <netinet/in.h>. Otherwise, you may try <sys/in.h>.

`i_poll`
  From i_poll.U:

  This variable conditionally defines the `I_POLL` symbol, and indicates whether a C program should include <poll.h>.

`i_prot`
  From i_prot.U:

  This variable conditionally defines the `I_PROT` symbol, and indicates whether a C program should include <prot.h>.

`i_pthread`
  From i_pthread.U:

  This variable conditionally defines the `I_PTHREAD` symbol, and indicates whether a C program should include <pthread.h>.

`i_pwd`
  From i_pwd.U:

  This variable conditionally defines `I_PWD`, which indicates to the C program that it should include <pwd.h>.

`i_rpcsvcdbm`
  From i_dbm.U:

  This variable conditionally defines the `I_RPCSVC_DBM` symbol, which indicates to the C program that <rpcsvc/dbm.h> exists and should be included. Some System V systems might need this instead of <dbm.h>.

`i_sfio`
  From i_sfio.U:

  This variable conditionally defines the `I_SFIO` symbol, and indicates whether a C program should include <sfio.h>.

`i_sgtty`
  From i_termio.U:

  This variable conditionally defines the `I_SGTTY` symbol, which indicates to the C program that it should include <sgtty.h> rather than <termio.h>.

`i_shadow`
  From i_shadow.U:

  This variable conditionally defines the `I_SHADOW` symbol, and indicates whether a C program should include <shadow.h>.

`i_socks`
  From i_socks.U:

  This variable conditionally defines the `I_SOCKS` symbol, and indicates whether a C program should include <socks.h>.

`i_stdarg`
  From i_varhdr.U:

  This variable conditionally defines the `I_STDARG` symbol, which indicates to the C program that <stdarg.h> exists and should be included.

`i_stddef`
  From i_stddef.U:

  This variable conditionally defines the `I_STDDEF` symbol, which indicates to the C program that <stddef.h> exists and should be included.

`i_stdlib`
  From i_stdlib.U:

  This variable conditionally defines the `I_STDLIB` symbol, which indicates to the C program that <stdlib.h> exists and should be included.

`i_string`
  From i_string.U:

  This variable conditionally defines the `I_STRING` symbol, which indicates that <string.h> should be included rather than <strings.h>.

`i_sunmath`
  From i_sunmath.U:

  This variable conditionally defines the `I_SUNMATH` symbol, and indicates whether a C program should include <sunmath.h>.

`i_sysaccess`
  From i_sysaccess.U:

  This variable conditionally defines the `I_SYS_ACCESS` symbol, and indicates whether a C program should include <sys/access.h>.

`i_sysdir`
  From i_sysdir.U:

  This variable conditionally defines the `I_SYS_DIR` symbol, and indicates whether a C program should include <sys/dir.h>.

`i_sysfile`
  From i_sysfile.U:

  This variable conditionally defines the `I_SYS_FILE` symbol, and indicates whether a C program should include <sys/file.h> to get `R_OK` and friends.

`i_sysfilio`
  From i_sysioctl.U:

  This variable conditionally defines the `I_SYS_FILIO` symbol, which indicates to the C program that <sys/filio.h> exists and should be included in preference to <sys/ioctl.h>.

`i_sysin`
  From i_niin.U:

  This variable conditionally defines `I_SYS_IN`, which indicates to the C program that it should include <sys/in.h> instead of <netinet/in.h>.

`i_sysioctl`
  From i_sysioctl.U:

  This variable conditionally defines the `I_SYS_IOCTL` symbol, which indicates to the C program that <sys/ioctl.h> exists and should be included.

`i_syslog`
  From i_syslog.U:

  This variable conditionally defines the `I_SYSLOG` symbol, and indicates whether a C program should include <syslog.h>.

`i_sysmman`
  From i_sysmman.U:

  This variable conditionally defines the `I_SYS_MMAN` symbol, and indicates whether a C program should include <sys/mman.h>.

`i_sysmode`
  From i_sysmode.U:

  This variable conditionally defines the `I_SYSMODE` symbol, and indicates whether a C program should include <sys/mode.h>.

`i_sysmount`
  From i_sysmount.U:

  This variable conditionally defines the `I_SYSMOUNT` symbol, and indicates whether a C program should include <sys/mount.h>.

`i_sysndir`
  From i_sysndir.U:

  This variable conditionally defines the `I_SYS_NDIR` symbol, and indicates whether a C program should include <sys/ndir.h>.

`i_sysparam`
  From i_sysparam.U:

  This variable conditionally defines the `I_SYS_PARAM` symbol, and indicates whether a C program should include <sys/param.h>.

`i_sysresrc`
  From i_sysresrc.U:

  This variable conditionally defines the `I_SYS_RESOURCE` symbol, and indicates whether a C program should include <sys/resource.h>.

`i_syssecrt`
  From i_syssecrt.U:

  This variable conditionally defines the `I_SYS_SECURITY` symbol, and indicates whether a C program should include <sys/security.h>.

`i_sysselct`
  From i_sysselct.U:

  This variable conditionally defines `I_SYS_SELECT`, which indicates to the C program that it should include <sys/select.h> in order to get the definition of struct timeval.

`i_syssockio`
  From i_sysioctl.U:

  This variable conditionally defines `I_SYS_SOCKIO` to indicate to the C program that socket ioctl codes may be found in <sys/sockio.h> instead of <sys/ioctl.h>.

`i_sysstat`
  From i_sysstat.U:

  This variable conditionally defines the `I_SYS_STAT` symbol, and indicates whether a C program should include <sys/stat.h>.

`i_sysstatfs`
  From i_sysstatfs.U:

  This variable conditionally defines the `I_SYSSTATFS` symbol, and indicates whether a C program should include <sys/statfs.h>.

`i_sysstatvfs`
  From i_sysstatvfs.U:

  This variable conditionally defines the `I_SYSSTATVFS` symbol, and indicates whether a C program should include <sys/statvfs.h>.

`i_systime`
  From i_time.U:

  This variable conditionally defines `I_SYS_TIME`, which indicates to the C program that it should include <sys/time.h>.

`i_systimek`
  From i_time.U:

  This variable conditionally defines `I_SYS_TIME_KERNEL`, which indicates to the C program that it should include <sys/time.h> with `KERNEL` defined.

`i_systimes`
  From i_systimes.U:

  This variable conditionally defines the `I_SYS_TIMES` symbol, and indicates whether a C program should include <sys/times.h>.

`i_systypes`
  From i_systypes.U:

  This variable conditionally defines the `I_SYS_TYPES` symbol, and indicates whether a C program should include <sys/types.h>.

`i_sysuio`
  From i_sysuio.U:

  This variable conditionally defines the `I_SYSUIO` symbol, and indicates whether a C program should include <sys/uio.h>.

`i_sysun`
  From i_sysun.U:

  This variable conditionally defines `I_SYS_UN`, which indicates to the C program that it should include <sys/un.h> to get `UNIX` domain socket definitions.

`i_sysutsname`
  From i_sysutsname.U:

  This variable conditionally defines the `I_SYSUTSNAME` symbol, and indicates whether a C program should include <sys/utsname.h>.

`i_sysvfs`
  From i_sysvfs.U:

  This variable conditionally defines the `I_SYSVFS` symbol, and indicates whether a C program should include <sys/vfs.h>.

`i_syswait`
  From i_syswait.U:

  This variable conditionally defines `I_SYS_WAIT`, which indicates to the C program that it should include <sys/wait.h>.

`i_termio`
  From i_termio.U:

  This variable conditionally defines the `I_TERMIO` symbol, which indicates to the C program that it should include <termio.h> rather than <sgtty.h>.

`i_termios`
  From i_termio.U:

  This variable conditionally defines the `I_TERMIOS` symbol, which indicates to the C program that the `POSIX` <termios.h> file is to be included.

`i_time`
  From i_time.U:

  This variable conditionally defines `I_TIME`, which indicates to the C program that it should include <time.h>.

`i_unistd`
  From i_unistd.U:

  This variable conditionally defines the `I_UNISTD` symbol, and indicates whether a C program should include <unistd.h>.

`i_ustat`
  From i_ustat.U:

  This variable conditionally defines the `I_USTAT` symbol, and indicates whether a C program should include <ustat.h>.

`i_utime`
  From i_utime.U:

  This variable conditionally defines the `I_UTIME` symbol, and indicates whether a C program should include <utime.h>.

`i_values`
  From i_values.U:

  This variable conditionally defines the `I_VALUES` symbol, and indicates whether a C program may include <values.h> to get symbols like `MAXLONG` and friends.

`i_varargs`
  From i_varhdr.U:

  This variable conditionally defines `I_VARARGS`, which indicates to the C program that it should include <varargs.h>.

`i_varhdr`
  From i_varhdr.U:

  Contains the name of the header to be included to get va_dcl definition. Typically one of varargs.h or stdarg.h.

`i_vfork`
  From i_vfork.U:

  This variable conditionally defines the `I_VFORK` symbol, and indicates whether a C program should include vfork.h.

`ignore_versioned_solibs`
  From libs.U:

  This variable should be non-empty if non-versioned shared libraries (libfoo.so.x.y) are to be ignored (because they cannot be linked against).

`inc_version_list`
  From inc_version_list.U:

  This variable specifies the list of subdirectories in over which perl.c:incpush() and lib/lib.pm will automatically search when adding directories to @`INC`. The elements in the list are separated by spaces. This is only useful if you have a perl library directory tree structured like the default one. See `INSTALL` for how this works. The versioned site_perl directory was introduced in 5.005, so that is the lowest possible value.

`inc_version_list_init`
  From inc_version_list.U:

  This variable holds the same list as inc_version_list, but each item is enclosed in double quotes and separated by commas, suitable for use in the `PERL_INC_VERSION_LIST` initialization.

`incpath`
  From usrinc.U:

  This variable must preceed the normal include path to get hte right one, as in $incpath/usr/include or $incpath/usr/lib. Value can be ``'' or /bsd43 on mips.

`inews`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`installarchlib`
  From archlib.U:

  This variable is really the same as archlibexp but may differ on those systems using `AFS`. For extra portability, only this variable should be used in makefiles.

`installbin`
  From bin.U:

  This variable is the same as binexp unless `AFS` is running in which case the user is explicitely prompted for it. This variable should always be used in your makefiles for maximum portability.

`installman1dir`
  From man1dir.U:

  This variable is really the same as man1direxp, unless you are using `AFS` in which case it points to the read/write location whereas man1direxp only points to the read-only access location. For extra portability, you should only use this variable within your makefiles.

`installman3dir`
  From man3dir.U:

  This variable is really the same as man3direxp, unless you are using `AFS` in which case it points to the read/write location whereas man3direxp only points to the read-only access location. For extra portability, you should only use this variable within your makefiles.

`installprefix`
  From installprefix.U:

  This variable holds the name of the directory below which ``make install'' will install the package. For most users, this is the same as prefix. However, it is useful for installing the software into a different (usually temporary) location after which it can be bundled up and moved somehow to the final location specified by prefix.

`installprefixexp`
  From installprefix.U:

  This variable holds the full absolute path of installprefix with all ~-expansion done.

`installprivlib`
  From privlib.U:

  This variable is really the same as privlibexp but may differ on those systems using `AFS`. For extra portability, only this variable should be used in makefiles.

`installscript`
  From scriptdir.U:

  This variable is usually the same as scriptdirexp, unless you are on a system running `AFS`, in which case they may differ slightly. You should always use this variable within your makefiles for portability.

`installsitearch`
  From sitearch.U:

  This variable is really the same as sitearchexp but may differ on those systems using `AFS`. For extra portability, only this variable should be used in makefiles.

`installsitebin`
  From sitebin.U:

  This variable is usually the same as sitebinexp, unless you are on a system running `AFS`, in which case they may differ slightly. You should always use this variable within your makefiles for portability.

`installsitelib`
  From sitelib.U:

  This variable is really the same as sitelibexp but may differ on those systems using `AFS`. For extra portability, only this variable should be used in makefiles.

`installstyle`
  From installstyle.U:

  This variable describes the `style` of the perl installation. This is intended to be useful for tools that need to manipulate entire perl distributions. Perl itself doesn't use this to find its libraries -- the library directories are stored directly in Config.pm. Currently, there are only two styles: `lib` and lib/perl5. The default library locations (e.g. privlib, sitelib) are either $prefix/lib or $prefix/lib/perl5. The former is useful if $prefix is a directory dedicated to perl (e.g. /opt/perl), while the latter is useful if $prefix is shared by many packages, e.g. if $prefix=/usr/local.

              This may later be extended to include other information, so

              be careful with pattern-matching on the results.

              For compatibility with F<perl5.005> and earlier, the default

              setting is based on whether or not $prefix contains the string
      C<perl>.

`installusrbinperl`
  From instubperl.U:

  This variable tells whether Perl should be installed also as /usr/bin/perl in addition to $installbin/perl

`installvendorarch`
  From vendorarch.U:

  This variable is really the same as vendorarchexp but may differ on those systems using `AFS`. For extra portability, only this variable should be used in makefiles.

`installvendorbin`
  From vendorbin.U:

  This variable is really the same as vendorbinexp but may differ on those systems using `AFS`. For extra portability, only this variable should be used in makefiles.

`installvendorlib`
  From vendorlib.U:

  This variable is really the same as vendorlibexp but may differ on those systems using `AFS`. For extra portability, only this variable should be used in makefiles.

`intsize`
  From intsize.U:

  This variable contains the value of the `INTSIZE` symbol, which indicates to the C program how many bytes there are in an int.

`issymlink`
  From issymlink.U:

  This variable holds the test command to test for a symbolic link (if they are supported). Typical values include `test -h` and `test -L`.

`ivdformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `IV` as a signed decimal integer.

`ivsize`
  From perlxv.U:

  This variable is the size of an `IV` in bytes.

`ivtype`
  From perlxv.U:

  This variable contains the C type used for Perl's `IV`.

## k

`known_extensions`
  From Extensions.U:

  This variable holds a list of all `XS` extensions included in the package.

`ksh`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

## l

`ld`
  From dlsrc.U:

  This variable indicates the program to be used to link libraries for dynamic loading. On some systems, it is `ld`. On `ELF` systems, it should be $cc. Mostly, we'll try to respect the hint file setting.

`lddlflags`
  From dlsrc.U:

  This variable contains any special flags that might need to be passed to $ld to create a shared library suitable for dynamic loading. It is up to the makefile to use it. For hpux, it should be `-b`. For sunos 4.1, it is empty.

`ldflags`
  From ccflags.U:

  This variable contains any additional C loader flags desired by the user. It is up to the Makefile to use this.

`ldflags_uselargefiles`
  From uselfs.U:

  This variable contains the loader flags needed by large file builds and added to ldflags by hints files.

`ldlibpthname`
  From libperl.U:

  This variable holds the name of the shared library search path, often `LD_LIBRARY_PATH`. To get an empty string, the hints file must set this to `none`.

`less`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the less program. After Configure runs, the value is reset to a plain `less` and is not useful.

`lib_ext`
  From Unix.U:

  This is an old synonym for _a.

`libc`
  From libc.U:

  This variable contains the location of the C library.

`libperl`
  From libperl.U:

  The perl executable is obtained by linking perlmain.c with libperl, any static extensions (usually just DynaLoader), and any other libraries needed on this system. libperl is usually libperl.a, but can also be libperl.so.xxx if the user wishes to build a perl executable with a shared library.

`libpth`
  From libpth.U:

  This variable holds the general path (space-separated) used to find libraries. It is intended to be used by other units.

`libs`
  From libs.U:

  This variable holds the additional libraries we want to use. It is up to the Makefile to deal with it.

`libsdirs`
  From libs.U:

  This variable holds the directory names aka dirnames of the libraries we found and accepted, duplicates are removed.

`libsfiles`
  From libs.U:

  This variable holds the filenames aka basenames of the libraries we found and accepted.

`libsfound`
  From libs.U:

  This variable holds the full pathnames of the libraries we found and accepted.

`libspath`
  From libs.U:

  This variable holds the directory names probed for libraries.

`libswanted`
  From Myinit.U:

  This variable holds a list of all the libraries we want to search. The order is chosen to pick up the c library ahead of ucb or bsd libraries for SVR4.

`libswanted_uselargefiles`
  From uselfs.U:

  This variable contains the libraries needed by large file builds and added to ldflags by hints files. It is a space separated list of the library names without the `lib` prefix or any suffix, just like libswanted..

`line`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`lint`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`lkflags`
  From ccflags.U:

  This variable contains any additional C partial linker flags desired by the user. It is up to the Makefile to use this.

`ln`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the ln program. After Configure runs, the value is reset to a plain `ln` and is not useful.

`lns`
  From lns.U:

  This variable holds the name of the command to make symbolic links (if they are supported). It can be used in the Makefile. It is either `ln -s` or `ln`

`locincpth`
  From ccflags.U:

  This variable contains a list of additional directories to be searched by the compiler. The appropriate `-I` directives will be added to ccflags. This is intended to simplify setting local directories from the Configure command line. It's not much, but it parallels the loclibpth stuff in libpth.U.

`loclibpth`
  From libpth.U:

  This variable holds the paths (space-separated) used to find local libraries. It is prepended to libpth, and is intended to be easily set from the command line.

`longdblsize`
  From d_longdbl.U:

  This variable contains the value of the `LONG_DOUBLESIZE` symbol, which indicates to the C program how many bytes there are in a long double, if this system supports long doubles.

`longlongsize`
  From d_longlong.U:

  This variable contains the value of the `LONGLONGSIZE` symbol, which indicates to the C program how many bytes there are in a long long, if this system supports long long.

`longsize`
  From intsize.U:

  This variable contains the value of the `LONGSIZE` symbol, which indicates to the C program how many bytes there are in a long.

`lp`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`lpr`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`ls`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the ls program. After Configure runs, the value is reset to a plain `ls` and is not useful.

`lseeksize`
  From lseektype.U:

  This variable defines lseektype to be something like off_t, long, or whatever type is used to declare lseek offset's type in the kernel (which also appears to be lseek's return type).

`lseektype`
  From lseektype.U:

  This variable defines lseektype to be something like off_t, long, or whatever type is used to declare lseek offset's type in the kernel (which also appears to be lseek's return type).

## m

`mail`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`mailx`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`make`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the make program. After Configure runs, the value is reset to a plain `make` and is not useful.

`make_set_make`
  From make.U:

  Some versions of `make` set the variable `MAKE`. Others do not. This variable contains the string to be included in Makefile.SH so that `MAKE` is set if needed, and not if not needed. Possible values are: make_set_make=`#` # If your make program handles this for you, make_set_make=`MAKE=$make` # if it doesn't. I used a comment character so that we can distinguish a `set` value (from a previous config.sh or Configure `-D` option) from an uncomputed value.

`mallocobj`
  From mallocsrc.U:

  This variable contains the name of the malloc.o that this package generates, if that malloc.o is preferred over the system malloc. Otherwise the value is null. This variable is intended for generating Makefiles. See mallocsrc.

`mallocsrc`
  From mallocsrc.U:

  This variable contains the name of the malloc.c that comes with the package, if that malloc.c is preferred over the system malloc. Otherwise the value is null. This variable is intended for generating Makefiles.

`malloctype`
  From mallocsrc.U:

  This variable contains the kind of ptr returned by malloc and realloc.

`man1dir`
  From man1dir.U:

  This variable contains the name of the directory in which manual source pages are to be put. It is the responsibility of the Makefile.SH to get the value of this into the proper command. You must be prepared to do the ~name expansion yourself.

`man1direxp`
  From man1dir.U:

  This variable is the same as the man1dir variable, but is filename expanded at configuration time, for convenient use in makefiles.

`man1ext`
  From man1dir.U:

  This variable contains the extension that the manual page should have: one of `n`, `l`, or `1`. The Makefile must supply the .. See man1dir.

`man3dir`
  From man3dir.U:

  This variable contains the name of the directory in which manual source pages are to be put. It is the responsibility of the Makefile.SH to get the value of this into the proper command. You must be prepared to do the ~name expansion yourself.

`man3direxp`
  From man3dir.U:

  This variable is the same as the man3dir variable, but is filename expanded at configuration time, for convenient use in makefiles.

`man3ext`
  From man3dir.U:

  This variable contains the extension that the manual page should have: one of `n`, `l`, or `3`. The Makefile must supply the .. See man3dir.

## M

`Mcc`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the Mcc program. After Configure runs, the value is reset to a plain `Mcc` and is not useful.

`mips_type`
  From usrinc.U:

  This variable holds the environment type for the mips system. Possible values are ``BSD 4.3'' and ``System V''.

`mkdir`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the mkdir program. After Configure runs, the value is reset to a plain `mkdir` and is not useful.

`mmaptype`
  From d_mmap.U:

  This symbol contains the type of pointer returned by `mmap()` (and simultaneously the type of the first argument). It can be `void *` or `caddr_t`.

`modetype`
  From modetype.U:

  This variable defines modetype to be something like mode_t, int, unsigned short, or whatever type is used to declare file modes for system calls.

`more`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the more program. After Configure runs, the value is reset to a plain `more` and is not useful.

`multiarch`
  From multiarch.U:

  This variable conditionally defines the `MULTIARCH` symbol which signifies the presence of multiplatform files. This is normally set by hints files.

`mv`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`myarchname`
  From archname.U:

  This variable holds the architecture name computed by Configure in a previous run. It is not intended to be perused by any user and should never be set in a hint file.

`mydomain`
  From myhostname.U:

  This variable contains the eventual value of the `MYDOMAIN` symbol, which is the domain of the host the program is going to run on. The domain must be appended to myhostname to form a complete host name. The dot comes with mydomain, and need not be supplied by the program.

`myhostname`
  From myhostname.U:

  This variable contains the eventual value of the `MYHOSTNAME` symbol, which is the name of the host the program is going to run on. The domain is not kept with hostname, but must be gotten from mydomain. The dot comes with mydomain, and need not be supplied by the program.

`myuname`
  From Oldconfig.U:

  The output of `uname -a` if available, otherwise the hostname. On Xenix, pseudo variables assignments in the output are stripped, thank you. The whole thing is then lower-cased.

## n

`n`
  From n.U:

  This variable contains the `-n` flag if that is what causes the echo command to suppress newline. Otherwise it is null. Correct usage is $echo $n ``prompt for a question: $c''.

`need_va_copy`
  From need_va_copy.U:

  This symbol, if defined, indicates that the system stores the variable argument list datatype, va_list, in a format that cannot be copied by simple assignment, so that some other means must be used when copying is required. As such systems vary in their provision (or non-provision) of copying mechanisms, handy.h defines a platform- `independent` macro, Perl_va_copy(src, dst), to do the job.

`netdb_hlen_type`
  From netdbtype.U:

  This variable holds the type used for the 2nd argument to gethostbyaddr(). Usually, this is int or size_t or unsigned. This is only useful if you have gethostbyaddr(), naturally.

`netdb_host_type`
  From netdbtype.U:

  This variable holds the type used for the 1st argument to gethostbyaddr(). Usually, this is char * or void *, possibly with or without a const prefix. This is only useful if you have gethostbyaddr(), naturally.

`netdb_name_type`
  From netdbtype.U:

  This variable holds the type used for the argument to gethostbyname(). Usually, this is char * or const char *. This is only useful if you have gethostbyname(), naturally.

`netdb_net_type`
  From netdbtype.U:

  This variable holds the type used for the 1st argument to getnetbyaddr(). Usually, this is int or long. This is only useful if you have getnetbyaddr(), naturally.

`nm`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the nm program. After Configure runs, the value is reset to a plain `nm` and is not useful.

`nm_opt`
  From usenm.U:

  This variable holds the options that may be necessary for nm.

`nm_so_opt`
  From usenm.U:

  This variable holds the options that may be necessary for nm to work on a shared library but that can not be used on an archive library. Currently, this is only used by Linux, where nm --dynamic is *required* to get symbols from an `ELF` library which has been stripped, but nm --dynamic is *fatal* on an archive library. Maybe Linux should just always set usenm=false.

`nonxs_ext`
  From Extensions.U:

  This variable holds a list of all non-xs extensions included in the package. All of them will be built.

`nroff`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the nroff program. After Configure runs, the value is reset to a plain `nroff` and is not useful.

`nveformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `NV` using %e-ish floating point format.

`nvEUformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `NV` using %E-ish floating point format.

`nvfformat`
  From perlxvf.U:

  This variable confains the format string used for printing a Perl `NV` using %f-ish floating point format.

`nvFUformat`
  From perlxvf.U:

  This variable confains the format string used for printing a Perl `NV` using %F-ish floating point format.

`nvgformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `NV` using %g-ish floating point format.

`nvGUformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `NV` using %G-ish floating point format.

`nvsize`
  From perlxv.U:

  This variable is the size of an `NV` in bytes.

`nvtype`
  From perlxv.U:

  This variable contains the C type used for Perl's `NV`.

## o

`o_nonblock`
  From nblock_io.U:

  This variable bears the symbol value to be used during `open()` or `fcntl()` to turn on non-blocking I/O for a file descriptor. If you wish to switch between blocking and non-blocking, you may try ioctl(`FIOSNBIO`) instead, but that is only supported by some devices.

`obj_ext`
  From Unix.U:

  This is an old synonym for _o.

`old_pthread_create_joinable`
  From d_pthrattrj.U:

  This variable defines the constant to use for creating joinable (aka undetached) pthreads. Unused if pthread.h defines `PTHREAD_CREATE_JOINABLE`. If used, possible values are `PTHREAD_CREATE_UNDETACHED` and `__UNDETACHED`.

`optimize`
  From ccflags.U:

  This variable contains any optimizer/debugger flag that should be used. It is up to the Makefile to use it.

`orderlib`
  From orderlib.U:

  This variable is `true` if the components of libraries must be ordered (with `lorder $* | tsort`) before placing them in an archive. Set to `false` if ranlib or ar can generate random libraries.

`osname`
  From Oldconfig.U:

  This variable contains the operating system name (e.g. sunos, solaris, hpux, etc.). It can be useful later on for setting defaults. Any spaces are replaced with underscores. It is set to a null string if we can't figure it out.

`osvers`
  From Oldconfig.U:

  This variable contains the operating system version (e.g. 4.1.3, 5.2, etc.). It is primarily used for helping select an appropriate hints file, but might be useful elsewhere for setting defaults. It is set to '' if we can't figure it out. We try to be flexible about how much of the version number to keep, e.g. if 4.1.1, 4.1.2, and 4.1.3 are essentially the same for this package, hints files might just be os_4.0 or os_4.1, etc., not keeping separate files for each little release.

`otherlibdirs`
  From otherlibdirs.U:

  This variable contains a colon-separated set of paths for the perl binary to search for additional library files or modules. These directories will be tacked to the end of @`INC`. Perl will automatically search below each path for version- and architecture-specific directories. See inc_version_list for more details. A value of `` means `none` and is used to preserve this value for the next run through Configure.

## p

`package`
  From package.U:

  This variable contains the name of the package being constructed. It is primarily intended for the use of later Configure units.

`pager`
  From pager.U:

  This variable contains the name of the preferred pager on the system. Usual values are (the full pathnames of) more, less, pg, or cat.

`passcat`
  From nis.U:

  This variable contains a command that produces the text of the /etc/passwd file. This is normally ``cat /etc/passwd'', but can be ``ypcat passwd'' when `NIS` is used. On some systems, such as os390, there may be no equivalent command, in which case this variable is unset.

`patchlevel`
  From patchlevel.U:

  The patchlevel level of this package. The value of patchlevel comes from the patchlevel.h file. In a version number such as 5.6.1, this is the `6`. In patchlevel.h, this is referred to as `PERL_VERSION`.

`path_sep`
  From Unix.U:

  This is an old synonym for p_ in Head.U, the character used to separate elements in the command shell search `PATH`.

`perl5`
  From perl5.U:

  This variable contains the full path (if any) to a previously installed perl5.005 or later suitable for running the script to determine inc_version_list.

`perl`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

## P

`PERL_REVISION`
  From Oldsyms.U:

  In a Perl version number such as 5.6.2, this is the 5. This value is manually set in patchlevel.h

`PERL_SUBVERSION`
  From Oldsyms.U:

  In a Perl version number such as 5.6.2, this is the 2. Values greater than 50 represent potentially unstable development subversions. This value is manually set in patchlevel.h

`PERL_VERSION`
  From Oldsyms.U:

  In a Perl version number such as 5.6.2, this is the 6. This value is manually set in patchlevel.h

`perladmin`
  From perladmin.U:

  Electronic mail address of the perl5 administrator.

`perllibs`
  From End.U:

  The list of libraries needed by Perl only (any libraries needed by extensions only will by dropped, if using dynamic loading).

`perlpath`
  From perlpath.U:

  This variable contains the eventual value of the `PERLPATH` symbol, which contains the name of the perl interpreter to be used in shell scripts and in the ``eval `exec`'' idiom.

`pg`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the pg program. After Configure runs, the value is reset to a plain `pg` and is not useful.

`phostname`
  From myhostname.U:

  This variable contains the eventual value of the `PHOSTNAME` symbol, which is a command that can be fed to `popen()` to get the host name. The program should probably not presume that the domain is or isn't there already.

`pidtype`
  From pidtype.U:

  This variable defines `PIDTYPE` to be something like pid_t, int, ushort, or whatever type is used to declare process ids in the kernel.

`plibpth`
  From libpth.U:

  Holds the private path used by Configure to find out the libraries. Its value is prepend to libpth. This variable takes care of special machines, like the mips. Usually, it should be empty.

`pm_apiversion`
  From xs_apiversion.U:

  This variable contains the version of the oldest perl compatible with the present perl. (That is, pure perl modules written for $pm_apiversion will still work for the current version). perl.c:incpush() and lib/lib.pm will automatically search in $sitelib for older directories across major versions back to pm_apiversion. This is only useful if you have a perl library directory tree structured like the default one. The versioned site_perl library was introduced in 5.005, so that's the default setting for this variable. It's hard to imagine it changing before Perl6. It is included here for symmetry with xs_apiveprsion -- the searching algorithms will (presumably) be similar. See the `INSTALL` file for how this works.

`pmake`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`pr`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`prefix`
  From prefix.U:

  This variable holds the name of the directory below which the user will install the package. Usually, this is /usr/local, and executables go in /usr/local/bin, library stuff in /usr/local/lib, man pages in /usr/local/man, etc. It is only used to set defaults for things in bin.U, mansrc.U, privlib.U, or scriptdir.U.

`prefixexp`
  From prefix.U:

  This variable holds the full absolute path of the directory below which the user will install the package. Derived from prefix.

`privlib`
  From privlib.U:

  This variable contains the eventual value of the `PRIVLIB` symbol, which is the name of the private library for this package. It may have a ~ on the front. It is up to the makefile to eventually create this directory while performing installation (with ~ substitution).

`privlibexp`
  From privlib.U:

  This variable is the ~name expanded version of privlib, so that you may use it directly in Makefiles or shell scripts.

`prototype`
  From prototype.U:

  This variable holds the eventual value of `CAN_PROTOTYPE`, which indicates the C compiler can handle funciton prototypes.

`ptrsize`
  From ptrsize.U:

  This variable contains the value of the `PTRSIZE` symbol, which indicates to the C program how many bytes there are in a pointer.

## q

`quadkind`
  From quadtype.U:

  This variable, if defined, encodes the type of a quad: 1 = int, 2 = long, 3 = long long, 4 = int64_t.

`quadtype`
  From quadtype.U:

  This variable defines Quad_t to be something like long, int, long long, int64_t, or whatever type is used for 64-bit integers.

## r

`randbits`
  From randfunc.U:

  Indicates how many bits are produced by the function used to generate normalized random numbers.

`randfunc`
  From randfunc.U:

  Indicates the name of the random number function to use. Values include drand48, random, and rand. In C programs, the `Drand01` macro is defined to generate uniformly distributed random numbers over the range [0., 1.[ (see drand01 and nrand).

`randseedtype`
  From randfunc.U:

  Indicates the type of the argument of the seedfunc.

`ranlib`
  From orderlib.U:

  This variable is set to the pathname of the ranlib program, if it is needed to generate random libraries. Set to `:` if ar can generate random libraries or if random libraries are not supported

`rd_nodata`
  From nblock_io.U:

  This variable holds the return code from `read()` when no data is present. It should be -1, but some systems return 0 when `O_NDELAY` is used, which is a shame because you cannot make the difference between no data and an EOF.. Sigh!

`revision`
  From patchlevel.U:

  The value of revision comes from the patchlevel.h file. In a version number such as 5.6.1, this is the `5`. In patchlevel.h, this is referred to as `PERL_REVISION`.

`rm`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the rm program. After Configure runs, the value is reset to a plain `rm` and is not useful.

`rmail`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`runnm`
  From usenm.U:

  This variable contains `true` or `false` depending whether the nm extraction should be performed or not, according to the value of usenm and the flags on the Configure command line.

## s

`sched_yield`
  From d_pthread_y.U:

  This variable defines the way to yield the execution of the current thread.

`scriptdir`
  From scriptdir.U:

  This variable holds the name of the directory in which the user wants to put publicly scripts for the package in question. It is either the same directory as for binaries, or a special one that can be mounted across different architectures, like /usr/share. Programs must be prepared to deal with ~name expansion.

`scriptdirexp`
  From scriptdir.U:

  This variable is the same as scriptdir, but is filename expanded at configuration time, for programs not wanting to bother with it.

`sed`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the sed program. After Configure runs, the value is reset to a plain `sed` and is not useful.

`seedfunc`
  From randfunc.U:

  Indicates the random number generating seed function. Values include srand48, srandom, and srand.

`selectminbits`
  From selectminbits.U:

  This variable holds the minimum number of bits operated by select. That is, if you do select(n, ...), how many bits at least will be cleared in the masks if some activity is detected. Usually this is either n or 32*ceil(n/32), especially many little-endians do the latter. This is only useful if you have select(), naturally.

`selecttype`
  From selecttype.U:

  This variable holds the type used for the 2nd, 3rd, and 4th arguments to select. Usually, this is `fd_set *`, if `HAS_FD_SET` is defined, and `int *` otherwise. This is only useful if you have select(), naturally.

`sendmail`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`sh`
  From sh.U:

  This variable contains the full pathname of the shell used on this system to execute Bourne shell scripts. Usually, this will be /bin/sh, though it's possible that some systems will have /bin/ksh, /bin/pdksh, /bin/ash, /bin/bash, or even something such as D:/bin/sh.exe. This unit comes before Options.U, so you can't set sh with a `-D` option, though you can override this (and startsh) with `-O -Dsh=/bin/whatever -Dstartsh=whatever`

`shar`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`sharpbang`
  From spitshell.U:

  This variable contains the string #! if this system supports that construct.

`shmattype`
  From d_shmat.U:

  This symbol contains the type of pointer returned by shmat(). It can be `void *` or `char *`.

`shortsize`
  From intsize.U:

  This variable contains the value of the `SHORTSIZE` symbol which indicates to the C program how many bytes there are in a short.

`shrpenv`
  From libperl.U:

  If the user builds a shared libperl.so, then we need to tell the `perl` executable where it will be able to find the installed libperl.so. One way to do this on some systems is to set the environment variable `LD_RUN_PATH` to the directory that will be the final location of the shared libperl.so. The makefile can use this with something like $shrpenv $(`CC`) -o perl perlmain.o $libperl $libs Typical values are shrpenv=``env `LD_RUN_PATH`=$archlibexp/`CORE`'' or shrpenv='' See the main perl Makefile.SH for actual working usage. Alternatively, we might be able to use a command line option such as -R $archlibexp/`CORE` (Solaris, NetBSD) or -Wl,-rpath $archlibexp/`CORE` (Linux).

`shsharp`
  From spitshell.U:

  This variable tells further Configure units whether your sh can handle # comments.

`sig_count`
  From sig_name.U:

  This variable holds a number larger than the largest valid signal number. This is usually the same as the `NSIG` macro.

`sig_name`
  From sig_name.U:

  This variable holds the signal names, space separated. The leading `SIG` in signal name is removed. A `ZERO` is prepended to the list. This is currently not used.

`sig_name_init`
  From sig_name.U:

  This variable holds the signal names, enclosed in double quotes and separated by commas, suitable for use in the `SIG_NAME` definition below. A `ZERO` is prepended to the list, and the list is terminated with a plain 0. The leading `SIG` in signal names is removed. See sig_num.

`sig_num`
  From sig_name.U:

  This variable holds the signal numbers, space separated. A `ZERO` is prepended to the list (corresponding to the fake `SIGZERO`), and the list is terminated with a 0. Those numbers correspond to the value of the signal listed in the same place within the sig_name list.

`sig_num_init`
  From sig_name.U:

  This variable holds the signal numbers, enclosed in double quotes and separated by commas, suitable for use in the `SIG_NUM` definition below. A `ZERO` is prepended to the list, and the list is terminated with a plain 0.

`sig_size`
  From sig_name.U:

  This variable contains the number of elements of the sig_name and sig_num arrays, excluding the final `NULL` entry.

`signal_t`
  From d_voidsig.U:

  This variable holds the type of the signal handler (void or int).

`sitearch`
  From sitearch.U:

  This variable contains the eventual value of the `SITEARCH` symbol, which is the name of the private library for this package. It may have a ~ on the front. It is up to the makefile to eventually create this directory while performing installation (with ~ substitution). The standard distribution will put nothing in this directory. After perl has been installed, users may install their own local architecture-dependent modules in this directory with MakeMaker Makefile.PL or equivalent. See `INSTALL` for details.

`sitearchexp`
  From sitearch.U:

  This variable is the ~name expanded version of sitearch, so that you may use it directly in Makefiles or shell scripts.

`sitebin`
  From sitebin.U:

  This variable holds the name of the directory in which the user wants to put add-on publicly executable files for the package in question. It is most often a local directory such as /usr/local/bin. Programs using this variable must be prepared to deal with ~name substitution. The standard distribution will put nothing in this directory. After perl has been installed, users may install their own local executables in this directory with MakeMaker Makefile.PL or equivalent. See `INSTALL` for details.

`sitebinexp`
  From sitebin.U:

  This is the same as the sitebin variable, but is filename expanded at configuration time, for use in your makefiles.

`sitelib`
  From sitelib.U:

  This variable contains the eventual value of the `SITELIB` symbol, which is the name of the private library for this package. It may have a ~ on the front. It is up to the makefile to eventually create this directory while performing installation (with ~ substitution). The standard distribution will put nothing in this directory. After perl has been installed, users may install their own local architecture-independent modules in this directory with MakeMaker Makefile.PL or equivalent. See `INSTALL` for details.

`sitelib_stem`
  From sitelib.U:

  This variable is $sitelibexp with any trailing version-specific component removed. The elements in inc_version_list (inc_version_list.U) can be tacked onto this variable to generate a list of directories to search.

`sitelibexp`
  From sitelib.U:

  This variable is the ~name expanded version of sitelib, so that you may use it directly in Makefiles or shell scripts.

`siteprefix`
  From siteprefix.U:

  This variable holds the full absolute path of the directory below which the user will install add-on packages. See `INSTALL` for usage and examples.

`siteprefixexp`
  From siteprefix.U:

  This variable holds the full absolute path of the directory below which the user will install add-on packages. Derived from siteprefix.

`sizesize`
  From sizesize.U:

  This variable contains the size of a sizetype in bytes.

`sizetype`
  From sizetype.U:

  This variable defines sizetype to be something like size_t, unsigned long, or whatever type is used to declare length parameters for string functions.

`sleep`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`smail`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`so`
  From so.U:

  This variable holds the extension used to identify shared libraries (also known as shared objects) on the system. Usually set to `so`.

`sockethdr`
  From d_socket.U:

  This variable has any cpp `-I` flags needed for socket support.

`socketlib`
  From d_socket.U:

  This variable has the names of any libraries needed for socket support.

`socksizetype`
  From socksizetype.U:

  This variable holds the type used for the size argument for various socket calls like accept. Usual values include socklen_t, size_t, and int.

`sort`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the sort program. After Configure runs, the value is reset to a plain `sort` and is not useful.

`spackage`
  From package.U:

  This variable contains the name of the package being constructed, with the first letter uppercased, i.e. suitable for starting sentences.

`spitshell`
  From spitshell.U:

  This variable contains the command necessary to spit out a runnable shell on this system. It is either cat or a grep `-v` for # comments.

`sPRId64`
  From quadfio.U:

  This variable, if defined, contains the string used by stdio to format 64-bit decimal numbers (format `d`) for output.

`sPRIeldbl`
  From longdblfio.U:

  This variable, if defined, contains the string used by stdio to format long doubles (format `e`) for output.

`sPRIEUldbl`
  From longdblfio.U:

  This variable, if defined, contains the string used by stdio to format long doubles (format `E`) for output. The `U` in the name is to separate this from sPRIeldbl so that even case-blind systems can see the difference.

`sPRIfldbl`
  From longdblfio.U:

  This variable, if defined, contains the string used by stdio to format long doubles (format `f`) for output.

`sPRIFUldbl`
  From longdblfio.U:

  This variable, if defined, contains the string used by stdio to format long doubles (format `F`) for output. The `U` in the name is to separate this from sPRIfldbl so that even case-blind systems can see the difference.

`sPRIgldbl`
  From longdblfio.U:

  This variable, if defined, contains the string used by stdio to format long doubles (format `g`) for output.

`sPRIGUldbl`
  From longdblfio.U:

  This variable, if defined, contains the string used by stdio to format long doubles (format `G`) for output. The `U` in the name is to separate this from sPRIgldbl so that even case-blind systems can see the difference.

`sPRIi64`
  From quadfio.U:

  This variable, if defined, contains the string used by stdio to format 64-bit decimal numbers (format `i`) for output.

`sPRIo64`
  From quadfio.U:

  This variable, if defined, contains the string used by stdio to format 64-bit octal numbers (format `o`) for output.

`sPRIu64`
  From quadfio.U:

  This variable, if defined, contains the string used by stdio to format 64-bit unsigned decimal numbers (format `u`) for output.

`sPRIx64`
  From quadfio.U:

  This variable, if defined, contains the string used by stdio to format 64-bit hexadecimal numbers (format `x`) for output.

`sPRIXU64`
  From quadfio.U:

  This variable, if defined, contains the string used by stdio to format 64-bit hExADECimAl numbers (format `X`) for output. The `U` in the name is to separate this from sPRIx64 so that even case-blind systems can see the difference.

`src`
  From src.U:

  This variable holds the path to the package source. It is up to the Makefile to use this variable and set `VPATH` accordingly to find the sources remotely.

`sSCNfldbl`
  From longdblfio.U:

  This variable, if defined, contains the string used by stdio to format long doubles (format `f`) for input.

`ssizetype`
  From ssizetype.U:

  This variable defines ssizetype to be something like ssize_t, long or int. It is used by functions that return a count of bytes or an error condition. It must be a signed type. We will pick a type such that `sizeof(SSize_t)` == sizeof(Size_t).

`startperl`
  From startperl.U:

  This variable contains the string to put on the front of a perl script to make sure (hopefully) that it runs with perl and not some shell. Of course, that leading line must be followed by the classical perl idiom: eval 'exec perl -S $0 ${1+`$@`}' if $running_under_some_shell; to guarantee perl startup should the shell execute the script. Note that this magic incatation is not understood by csh.

`startsh`
  From startsh.U:

  This variable contains the string to put on the front of a shell script to make sure (hopefully) that it runs with sh and not some other shell.

`static_ext`
  From Extensions.U:

  This variable holds a list of `XS` extension files we want to link statically into the package. It is used by Makefile.

`stdchar`
  From stdchar.U:

  This variable conditionally defines `STDCHAR` to be the type of char used in stdio.h. It has the values ``unsigned char'' or `char`.

`stdio_base`
  From d_stdstdio.U:

  This variable defines how, given a `FILE` pointer, fp, to access the _base field (or equivalent) of stdio.h's `FILE` structure. This will be used to define the macro FILE_base(fp).

`stdio_bufsiz`
  From d_stdstdio.U:

  This variable defines how, given a `FILE` pointer, fp, to determine the number of bytes store in the I/O buffer pointer to by the _base field (or equivalent) of stdio.h's `FILE` structure. This will be used to define the macro FILE_bufsiz(fp).

`stdio_cnt`
  From d_stdstdio.U:

  This variable defines how, given a `FILE` pointer, fp, to access the _cnt field (or equivalent) of stdio.h's `FILE` structure. This will be used to define the macro FILE_cnt(fp).

`stdio_filbuf`
  From d_stdstdio.U:

  This variable defines how, given a `FILE` pointer, fp, to tell stdio to refill it's internal buffers (?). This will be used to define the macro FILE_filbuf(fp).

`stdio_ptr`
  From d_stdstdio.U:

  This variable defines how, given a `FILE` pointer, fp, to access the _ptr field (or equivalent) of stdio.h's `FILE` structure. This will be used to define the macro FILE_ptr(fp).

`stdio_stream_array`
  From stdio_streams.U:

  This variable tells the name of the array holding the stdio streams. Usual values include _iob, __iob, and __sF.

`strings`
  From i_string.U:

  This variable holds the full path of the string header that will be used. Typically /usr/include/string.h or /usr/include/strings.h.

`submit`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`subversion`
  From patchlevel.U:

  The subversion level of this package. The value of subversion comes from the patchlevel.h file. In a version number such as 5.6.1, this is the `1`. In patchlevel.h, this is referred to as `PERL_SUBVERSION`. This is unique to perl.

`sysman`
  From sysman.U:

  This variable holds the place where the manual is located on this system. It is not the place where the user wants to put his manual pages. Rather it is the place where Configure may look to find manual for unix commands (section 1 of the manual usually). See mansrc.

## t

`tail`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`tar`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`tbl`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`tee`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`test`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the test program. After Configure runs, the value is reset to a plain `test` and is not useful.

`timeincl`
  From i_time.U:

  This variable holds the full path of the included time header(s).

`timetype`
  From d_time.U:

  This variable holds the type returned by time(). It can be long, or time_t on `BSD` sites (in which case <sys/types.h> should be included). Anyway, the type Time_t should be used.

`touch`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the touch program. After Configure runs, the value is reset to a plain `touch` and is not useful.

`tr`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the tr program. After Configure runs, the value is reset to a plain `tr` and is not useful.

`trnl`
  From trnl.U:

  This variable contains the value to be passed to the `tr(1)` command to transliterate a newline. Typical values are `\012` and `\n`. This is needed for `EBCDIC` systems where newline is not necessarily `\012`.

`troff`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

## u

`u16size`
  From perlxv.U:

  This variable is the size of an U16 in bytes.

`u16type`
  From perlxv.U:

  This variable contains the C type used for Perl's U16.

`u32size`
  From perlxv.U:

  This variable is the size of an U32 in bytes.

`u32type`
  From perlxv.U:

  This variable contains the C type used for Perl's U32.

`u64size`
  From perlxv.U:

  This variable is the size of an U64 in bytes.

`u64type`
  From perlxv.U:

  This variable contains the C type used for Perl's U64.

`u8size`
  From perlxv.U:

  This variable is the size of an U8 in bytes.

`u8type`
  From perlxv.U:

  This variable contains the C type used for Perl's U8.

`uidformat`
  From uidf.U:

  This variable contains the format string used for printing a Uid_t.

`uidsign`
  From uidsign.U:

  This variable contains the signedness of a uidtype. 1 for unsigned, -1 for signed.

`uidsize`
  From uidsize.U:

  This variable contains the size of a uidtype in bytes.

`uidtype`
  From uidtype.U:

  This variable defines Uid_t to be something like uid_t, int, ushort, or whatever type is used to declare user ids in the kernel.

`uname`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the uname program. After Configure runs, the value is reset to a plain `uname` and is not useful.

`uniq`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the uniq program. After Configure runs, the value is reset to a plain `uniq` and is not useful.

`uquadtype`
  From quadtype.U:

  This variable defines Uquad_t to be something like unsigned long, unsigned int, unsigned long long, uint64_t, or whatever type is used for 64-bit integers.

`use5005threads`
  From usethreads.U:

  This variable conditionally defines the USE_5005THREADS symbol, and indicates that Perl should be built to use the 5.005-based threading implementation.

`use64bitall`
  From use64bits.U:

  This variable conditionally defines the USE_64_BIT_ALL symbol, and indicates that 64-bit integer types should be used when available. The maximal possible 64-bitness is employed: LP64 or ILP64, meaning that you will be able to use more than 2 gigabytes of memory. This mode is even more binary incompatible than USE_64_BIT_INT. You may not be able to run the resulting executable in a 32-bit `CPU` at all or you may need at least to reboot your `OS` to 64-bit mode.

`use64bitint`
  From use64bits.U:

  This variable conditionally defines the USE_64_BIT_INT symbol, and indicates that 64-bit integer types should be used when available. The minimal possible 64-bitness is employed, just enough to get 64-bit integers into Perl. This may mean using for example ``long longs'', while your memory may still be limited to 2 gigabytes.

`usedl`
  From dlsrc.U:

  This variable indicates if the system supports dynamic loading of some sort. See also dlsrc and dlobj.

`useithreads`
  From usethreads.U:

  This variable conditionally defines the `USE_ITHREADS` symbol, and indicates that Perl should be built to use the interpreter-based threading implementation.

`uselargefiles`
  From uselfs.U:

  This variable conditionally defines the `USE_LARGE_FILES` symbol, and indicates that large file interfaces should be used when available.

`uselongdouble`
  From uselongdbl.U:

  This variable conditionally defines the `USE_LONG_DOUBLE` symbol, and indicates that long doubles should be used when available.

`usemorebits`
  From usemorebits.U:

  This variable conditionally defines the `USE_MORE_BITS` symbol, and indicates that explicit 64-bit interfaces and long doubles should be used when available.

`usemultiplicity`
  From usemultiplicity.U:

  This variable conditionally defines the `MULTIPLICITY` symbol, and indicates that Perl should be built to use multiplicity.

`usemymalloc`
  From mallocsrc.U:

  This variable contains y if the malloc that comes with this package is desired over the system's version of malloc. People often include special versions of malloc for effiency, but such versions are often less portable. See also mallocsrc and mallocobj. If this is `y`, then -lmalloc is removed from $libs.

`usenm`
  From usenm.U:

  This variable contains `true` or `false` depending whether the nm extraction is wanted or not.

`useopcode`
  From Extensions.U:

  This variable holds either `true` or `false` to indicate whether the Opcode extension should be used. The sole use for this currently is to allow an easy mechanism for users to skip the Opcode extension from the Configure command line.

`useperlio`
  From useperlio.U:

  This variable conditionally defines the `USE_PERLIO` symbol, and indicates that the PerlIO abstraction should be used throughout.

`useposix`
  From Extensions.U:

  This variable holds either `true` or `false` to indicate whether the `POSIX` extension should be used. The sole use for this currently is to allow an easy mechanism for hints files to indicate that `POSIX` will not compile on a particular system.

`usesfio`
  From d_sfio.U:

  This variable is set to true when the user agrees to use sfio. It is set to false when sfio is not available or when the user explicitely requests not to use sfio. It is here primarily so that command-line settings can override the auto-detection of d_sfio without running into a ``WHOA THERE''.

`useshrplib`
  From libperl.U:

  This variable is set to `yes` if the user wishes to build a shared libperl, and `no` otherwise.

`usesocks`
  From usesocks.U:

  This variable conditionally defines the `USE_SOCKS` symbol, and indicates that Perl should be built to use `SOCKS`.

`usethreads`
  From usethreads.U:

  This variable conditionally defines the `USE_THREADS` symbol, and indicates that Perl should be built to use threads.

`usevendorprefix`
  From vendorprefix.U:

  This variable tells whether the vendorprefix and consequently other vendor* paths are in use.

`usevfork`
  From d_vfork.U:

  This variable is set to true when the user accepts to use vfork. It is set to false when no vfork is available or when the user explicitely requests not to use vfork.

`usrinc`
  From usrinc.U:

  This variable holds the path of the include files, which is usually /usr/include. It is mainly used by other Configure units.

`uuname`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`uvoformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `UV` as an unsigned octal integer.

`uvsize`
  From perlxv.U:

  This variable is the size of a `UV` in bytes.

`uvtype`
  From perlxv.U:

  This variable contains the C type used for Perl's `UV`.

`uvuformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `UV` as an unsigned decimal integer.

`uvxformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `UV` as an unsigned hexadecimal integer in lowercase abcdef.

`uvXUformat`
  From perlxvf.U:

  This variable contains the format string used for printing a Perl `UV` as an unsigned hexadecimal integer in uppercase `ABCDEF`.

## v

`vendorarch`
  From vendorarch.U:

  This variable contains the value of the `PERL_VENDORARCH` symbol. It may have a ~ on the front. The standard distribution will put nothing in this directory. Vendors who distribute perl may wish to place their own architecture-dependent modules and extensions in this directory with MakeMaker Makefile.PL `INSTALLDIRS`=vendor or equivalent. See `INSTALL` for details.

`vendorarchexp`
  From vendorarch.U:

  This variable is the ~name expanded version of vendorarch, so that you may use it directly in Makefiles or shell scripts.

`vendorbin`
  From vendorbin.U:

  This variable contains the eventual value of the `VENDORBIN` symbol. It may have a ~ on the front. The standard distribution will put nothing in this directory. Vendors who distribute perl may wish to place additional binaries in this directory with MakeMaker Makefile.PL `INSTALLDIRS`=vendor or equivalent. See `INSTALL` for details.

`vendorbinexp`
  From vendorbin.U:

  This variable is the ~name expanded version of vendorbin, so that you may use it directly in Makefiles or shell scripts.

`vendorlib`
  From vendorlib.U:

  This variable contains the eventual value of the `VENDORLIB` symbol, which is the name of the private library for this package. The standard distribution will put nothing in this directory. Vendors who distribute perl may wish to place their own modules in this directory with MakeMaker Makefile.PL `INSTALLDIRS`=vendor or equivalent. See `INSTALL` for details.

`vendorlib_stem`
  From vendorlib.U:

  This variable is $vendorlibexp with any trailing version-specific component removed. The elements in inc_version_list (inc_version_list.U) can be tacked onto this variable to generate a list of directories to search.

`vendorlibexp`
  From vendorlib.U:

  This variable is the ~name expanded version of vendorlib, so that you may use it directly in Makefiles or shell scripts.

`vendorprefix`
  From vendorprefix.U:

  This variable holds the full absolute path of the directory below which the vendor will install add-on packages. See `INSTALL` for usage and examples.

`vendorprefixexp`
  From vendorprefix.U:

  This variable holds the full absolute path of the directory below which the vendor will install add-on packages. Derived from vendorprefix.

`version`
  From patchlevel.U:

  The full version number of this package, such as 5.6.1 (or 5_6_1). This combines revision, patchlevel, and subversion to get the full version number, including any possible subversions. This is suitable for use as a directory name, and hence is filesystem dependent.

`versiononly`
  From versiononly.U:

  If set, this symbol indicates that only the version-specific components of a perl installation should be installed. This may be useful for making a test installation of a new version without disturbing the existing installation. Setting versiononly is equivalent to setting installperl's -v option. In particular, the non-versioned scripts and programs such as a2p, c2ph, h2xs, pod2*, and perldoc are not installed (see `INSTALL` for a more complete list). Nor are the man pages installed. Usually, this is undef.

`vi`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`voidflags`
  From voidflags.U:

  This variable contains the eventual value of the `VOIDFLAGS` symbol, which indicates how much support of the void type is given by this compiler. See `VOIDFLAGS` for more info.

## x

`xlibpth`
  From libpth.U:

  This variable holds extra path (space-separated) used to find libraries on this platform, for example `CPU`-specific libraries (on multi-`CPU` platforms) may be listed here.

`xs_apiversion`
  From xs_apiversion.U:

  This variable contains the version of the oldest perl binary compatible with the present perl. perl.c:incpush() and lib/lib.pm will automatically search in $sitearch for older directories across major versions back to xs_apiversion. This is only useful if you have a perl library directory tree structured like the default one. See `INSTALL` for how this works. The versioned site_perl directory was introduced in 5.005, so that is the lowest possible value. Since this can depend on compile time options (such as bincompat) it is set by Configure. Other non-default sources of potential incompatibility, such as multiplicity, threads, debugging, 64bits, sfio, etc., are not checked for currently, though in principle we could go snooping around in old Config.pm files.

## z

`zcat`
  From Loc.U:

  This variable is defined but not used by Configure. The value is a plain '' and is not useful.

`zip`
  From Loc.U:

  This variable is used internally by Configure to determine the full pathname (if any) of the zip program. After Configure runs, the value is reset to a plain `zip` and is not useful.

# NOTE

This module contains a good example of how to use tie to implement a cache and an example of how to make a tied variable readonly to those outside of it.

Config - access Perl configuration information