File::Which (3pm)

  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

\*(C`File::Which\*(C' 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.

\*(C`File::Which\*(C' searches the directories of the user's \*(C`PATH\*(C' (as returned by \*(C`File::Spec->path()\*(C'), looking for executable files having the name specified as a parameter to \*(C`which()\*(C'. Under Win32 systems, which do not have a notion of directly executable files, but uses special extensions such as \*(C`.exe\*(C' and \*(C`.bat\*(C' to identify them, \*(C`File::Which\*(C' takes extra steps to assure that you will find the correct file (so for example, you might be searching for \*(C`perl\*(C', it'll try perl.exe, perl.bat, etc.)

Windows \s-1NT\s0

Windows \s-1NT\s0 has a special environment variable called \*(C`PATHEXT\*(C', which is used by the shell to look for executable files. Usually, it will contain a list in the form \*(C`.EXE;.BAT;.COM;.JS;.VBS\*(C' etc. If \*(C`File::Which\*(C' 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 \*(C`PATHEXT\*(C' variable, and usually you will find executable files there with the extensions \*(C`.exe\*(C', \*(C`.bat\*(C' and (less likely) \*(C`.com\*(C'. \*(C`File::Which\*(C' uses this hardcoded list if it's running under Win32 but does not find a \*(C`PATHEXT\*(C' variable.

\s-1VMS\s0

Same case as Windows 9x: uses \*(C`.exe\*(C' and \*(C`.com\*(C' (in that order).

which($short_exe_name)

Exported by default.

$short_exe_name is the name used in the shell to call the program (for example, \*(C`perl\*(C').

If it finds an executable with the name you specified, \*(C`which()\*(C' 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 \*(C`undef\*(C'.

If \*(C`which()\*(C' is called in list context, it will return all the matches.

where($short_exe_name)

Not exported by default.

Same as \*(C`which($short_exe_name)\*(C' in array context. Same as the `where' utility, will return an array containing all the path names matching $short_exe_name.

Not tested on \s-1VMS\s0 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 \s-1PATH\s0 if on Win32, \s-1VMS\s0 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 \s-1CPAN\s0 bug tracker at

http://rt.cpan.org/NoAuth/ReportBug.html?Queue=File-Which <http://rt.cpan.org/NoAuth/ReportBug.html?Queue=File-Which>

For other issues, contact the maintainer.

Adam Kennedy <[email protected]>

Per Einar Ellefsen <[email protected]>

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 \*(C`File::Which\*(C'.

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>.