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Config(3)                                                            Config(3)



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 the Switches entry 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 the Switches entry in the perlrun manpage.

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

         use Config;
         use strict;





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Config(3)                                                            Config(3)



         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.

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.
























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