File::Which(3) User Contributed Perl Documentation File::Which(3)
File::Which - Portable implementation of the `which' utility
use File::Which; # exports which()
use File::Which qw(which where); # exports which() and where()
my $exe_path = which('perldoc');
my @paths = where('perl');
- Or -
my @paths = which('perl'); # an array forces search for all of them
"File::Which" was created to be able to get the paths to executable programs on systems
under which the `which' program wasn't implemented in the shell.
"File::Which" searches the directories of the user's "PATH" (as returned by
"File::Spec->path()"), looking for executable files having the name specified as a
parameter to "which()". Under Win32 systems, which do not have a notion of directly
executable files, but uses special extensions such as ".exe" and ".bat" to identify them,
"File::Which" takes extra steps to assure that you will find the correct file (so for
example, you might be searching for "perl", it'll try perl.exe, perl.bat, etc.)
Steps Used on Win32, DOS, OS2 and VMS
Windows NT has a special environment variable called "PATHEXT", which is used by the shell
to look for executable files. Usually, it will contain a list in the form
".EXE;.BAT;.COM;.JS;.VBS" etc. If "File::Which" finds such an environment variable, it
parses the list and uses it as the different extensions.
Windows 9x and other ancient Win/DOS/OS2
This set of operating systems don't have the "PATHEXT" variable, and usually you will find
executable files there with the extensions ".exe", ".bat" and (less likely) ".com".
"File::Which" uses this hardcoded list if it's running under Win32 but does not find a
Same case as Windows 9x: uses ".exe" and ".com" (in that order).
Exported by default.
$short_exe_name is the name used in the shell to call the program (for example, "perl").
If it finds an executable with the name you specified, "which()" will return the absolute
path leading to this executable (for example, /usr/bin/perl or C:\Perl\Bin\perl.exe).
If it does not find the executable, it returns "undef".
If "which()" is called in list context, it will return all the matches.
Not exported by default.
Same as "which($short_exe_name)" in array context. Same as the `where' utility, will
return an array containing all the path names matching $short_exe_name.
BUGS AND CAVEATS
Not tested on VMS or MacOS, although there is platform specific code for those. Anyone who
haves a second would be very kind to send me a report of how it went.
File::Spec adds the current directory to the front of PATH if on Win32, VMS or MacOS. I
have no knowledge of those so don't know if the current directory is searced first or not.
Could someone please tell me?
Bugs should be reported via the CPAN bug tracker at
For other issues, contact the maintainer.
Adam Kennedy <firstname.lastname@example.org>
Per Einar Ellefsen <email@example.com>
Originated in modperl-2.0/lib/Apache/Build.pm. Changed for use in DocSet (for the mod_perl
site) and Win32-awareness by me, with slight modifications by Stas Bekman, then extracted
to create "File::Which".
Version 0.04 had some significant platform-related changes, taken from the Perl Power
Tools `which' implementation by Abigail with enhancements from Peter Prymmer. See
<http://www.perl.com/language/ppt/src/which/index.html> for more information.
Copyright 2002 Per Einar Ellefsen.
Some parts copyright 2009 Adam Kennedy.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
File::Spec, which(1), Perl Power Tools: <http://www.perl.com/language/ppt/index.html>.
perl v5.16.3 2009-09-26 File::Which(3)