MAN page from Old RedHat 5.X perl-5.004-4.i386.rpm

Config

Section: Perl Programmers Reference Guide (3)
Updated: perl 5.004, patch 04
Index

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 tothe Configure program at Perl build time (over 900 values).

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

Values stored in config.sh as `undef' are returned as undefinedvalues. The perl exists function can be used to check if anamed variable exists.

myconfig()

Returns a textual summary of the major perl configuration values.See also -V in the Switches entry in the perlrun manpage.

config_sh()

Returns the entire perl configuration information in the form of theoriginal config.sh shell variable assignment script.

config_vars(@names)

Prints to STDOUT the values of the named configuration variable. Each isprinted on a separate line in the form:

  name='value';

Names which are unknown are output as name='UNKNOWN';.See also -V:name in the Switches entry 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 executableitself it is possible (but unlikely) that the information does notrelate to the actual perl binary which is being used to access it.

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

NOTE

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

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