Config - access Perl configuration information
use Config;
if ($Config{'cc'} =~ /gcc/) {
print "built by gcc\n";
}
use Config qw(myconfig config_sh config_vars);
print myconfig();
print config_sh();
config_vars(qw(osname archname));
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The Config module contains all the information that was available to the Configure
program at Perl build time (over 900 values).
Shell variables from the config.sh file (written by Configure) are stored in the
readonly-variable %Config, indexed by their names.
Values stored in config.sh as 'undef' are returned as undefined values. The perl exists
function can be used to check if a named variable exists.
- myconfig()
- Returns a textual summary of the major perl configuration values. See also
-V
in perlrun/Switches.
- config_sh()
- Returns the entire perl configuration information in the form of the original config.sh
shell variable assignment script.
- config_vars(@names)
-
Prints to STDOUT the values of the named configuration variable. Each is printed on a
separate line in the form:
Names which are unknown are output as name='UNKNOWN';. See also -V:name
in perlrun/Switches.
Here's a more sophisticated example of using %Config:
use Config;
use strict;
my %sig_num;
my @sig_name;
unless($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 $sig_num{ALRM}\n";
}
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Because this information is not stored within the perl executable itself it is possible
(but unlikely) that the information does not relate to the actual perl binary which is being
used to access it.
The Config module is installed into the architecture and version specific library directory
($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)
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 library files. 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. DJGPP,
Cygwin and OS/2 use .exe. Stratus VOS uses .pm. On
operating systems which do not require a specific extension for executable files, this
variable is empty.
_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.
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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