Section: User Contributed Perl Documentation (3pm)
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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
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
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
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"
(less likely) ".com"
uses this hardcoded list if it's running
under Win32 but does not find a "PATHEXT"
Same case as Windows 9x: uses ".exe"
(in that order).
Exported by default.
$short_exe_name is the name used in the shell to call the program (for
If it finds an executable with the name you specified, "which()" will return
the absolute path leading to this executable (for example, /usr/bin/perl or
If it does not find the executable, it returns "undef".
If "which()" is called in list context, it will return all the
Not exported by default.
Same as "which($short_exe_name)" in array context. Same as the
`where' utility, will return an array containing all the path names
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
Bugs should be reported via the CPAN
bug tracker at
For other issues, contact the maintainer.
Adam Kennedy <email@example.com
Per Einar Ellefsen <firstname.lastname@example.org>
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
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.
(1), Perl Power Tools:
- Steps Used on Win32, DOS, OS2 and VMS
- Windows NT
- Windows 9x and other ancient Win/DOS/OS2
- BUGS AND CAVEATS
- SEE ALSO