Config - access Perl configuration information
use Config; if ($Config{'cc'} =~ /gcc/) { print "built by gcc\n"; }
use Config qw(myconfig config_sh config_vars);
print myconfig();
print config_sh();
config_vars(qw(osname archname));
The Config module contains all the information that was available to the Configure
program at Perl build time (over 900 values).
Shell variables from the config.sh file (written by Configure) are stored in the readonly-variable %Config
, indexed by their names.
Values stored in config.sh as 'undef' are returned as undefined values. The perl exists function can be used to check if a named variable exists.
-V
in Switches.
name='value';
Names which are unknown are output as name='UNKNOWN';
. See also -V:name
in Switches.
Here's a more sophisticated example of using %Config:
use Config; use strict;
my %sig_num; my @sig_name; unless($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 $sig_num{ALRM}\n"; }
Because this information is not stored within the perl executable itself it is possible (but unlikely) that the information does not relate to the actual perl binary which is being used to access it.
The Config module is installed into the architecture and version specific library directory ($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.
ENDOFTAIL
open(GLOS,
``<$glossary'') or die ``Can't open $glossary: $!''; %seen
= (); $text
= 0; $/ = '';
sub process { s/\A(\w*)\s+\(([\w.]+)\):\s*\n(\t?)/=item $1
\n\nFrom $2:\n\n/m; my $c
= substr $1, 0, 1; unless ($seen{$c}++) { print
CONFIG
<<EOF if $text; =back
EOF print
CONFIG
<<EOF; =head2 $c
EOF $text
= 1; } s/n't/n\00t/g; # leave
can't, won't etc untouched s/^\t\s+(.*)/\n\t$1\n/gm; # Indented lines
===> paragraphs s/^(?<!\n\n)\t(.*)/$1/gm; # Not indented lines ===> text
s{([\'\``])(?=[^\'\''\s]*[./][^\'\``\s]*\1)([^\'\''\s]+)\1}($2)g; # '.o' s{([\'\``])([^\'\''\s]+)\1}($2
)g; # ``date'' command s{\'([A-Za-z_\- *=/]+)\'}($1
)g; # 'ln -s' s{ (?<! [\w./<\'\``] ) # Only standalone file names (?! e \. g \. ) # Not e.g. (?! \. \.
\. ) # Not ... (?! \d ) # Not 5.004 ( [\w./]* [./] [\w./]* ) # Require . or
/ inside (?<! \. (?= \s ) ) # Do not include trailing dot (?! [\w/] ) # Include all of
it } ($1)xg; # /usr/local s/((?<=\s)~\w*)/$1/g; # ~name s/(?<![.<\'\``])\b([A-Z_]{2,})\b(?![\'\''])/$1
/g; #
UNISTD s/(?<![.<\'\``])\b(?!the\b)(\w+)\s+macro\b/$1
macro/g; # FILE_cnt macro s/n[\0]t/n't/g; # undo can't, won't damage }
<GLOS>; # Skip the preamble while (<GLOS>) { process; print CONFIG; }
print CONFIG <<'ENDOFTAIL';
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.
If rather than formatting bugs, you encounter substantive content errors in these documents, such as mistakes in the explanations or code, please use the perlbug utility included with the Perl distribution.