Perl Modules /Config.pm

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 Config - access Perl configuration information

 Config - access Perl configuration information

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 perlrun/Switches.

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 perlrun/Switches.

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, Mcc, cc -M, and gcc.

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.

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.

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_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_clos