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

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 PATHEXT variable.


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?


Per Einar Ellefsen, <per.einar (at)>

Originated in modperl-2.0/lib/Apache/ 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 for more information.


This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See Also

File::Spec, which(1), Perl Power Tools: .