Ubuntu Manpage: File::Which - Perl implementation of the which utility as an API

Provided by: libfile-which-perl_1.19-1_all

NAME

       File::Which - Perl implementation of the which utility as an API

VERSION

       version 1.19

SYNOPSIS

        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

DESCRIPTION

File::Which finds the full or relative paths to executable programs on the system. This
is normally the function of "which" utility. "which" is typically implemented as either a
program or a built in shell command. On some platforms, such as Microsoft Windows it is
not provided as part of the core operating system. This module provides a consistent API
to this functionality regardless of the underlying platform.

The focus of this module is correctness and portability. As a consequence platforms where
the current directory is implicitly part of the search path such as Microsoft Windows will
find executables in the current directory, whereas on platforms such as UNIX where this is
not the case executables in the current directory will only be found if the current
directory is explicitly added to the path.

If you need a portable "which" on the command line in an environment that does not provide
it, install App::pwhich which provides a command line interface to this API.

Implementations
File::Which searches the directories of the user's "PATH" (the current implementation uses
File::Spec#path to determine the correct "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.)

Linux, *BSD and other UNIXes

There should not be any surprises here. The current directory will not be searched unless
it is explicitly added to the path.

Modern Windows (including NT, XP, Vista, 7, 8, 10 etc)

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.

Cygwin

Cygwin provides a Unix-like environment for Microsoft Windows users. In most ways it
works like other Unix and Unix-like environments, but in a few key aspects it works like
Windows. As with other Unix environments, the current directory is not included in the
search unless it is explicitly included in the search path. Like on Windows, files with
".EXE" or <.BAT> extensions will be discovered even if they are not part of the query.
".COM" or extensions specified using the "PATHEXT" environment variable will NOT be
discovered without the fully qualified name, however.

Windows 95, 98, ME, MS-DOS, OS/2

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.

As of 2015 none of these platforms are tested frequently (or perhaps ever), but the
current maintainer is determined not to intentionally remove support for older operating
systems.

VMS

Same case as Windows 9x: uses ".exe" and ".com" (in that order).

As of 2015 the current maintainer does not test on VMS, and is in fact not certain it has
ever been tested on VMS. If this platform is important to you and you can help me verify
and or support it on that platform please contact me.

FUNCTIONS

   which
        my $path = which $short_exe_name;
        my @paths = which $short_exe_name;

       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.

   where
        my @paths = where $short_exe_name;

       Not exported by default.

       Same as "which" in array context. Same as the "where" utility, will return an array
       containing all the path names matching $short_exe_name.

CAVEATS

       This module has no non-core requirements for Perl 5.6.2 and better.

       This module is fully supported back to Perl 5.8.1.  It may work on 5.8.0.  It should work
       on Perl 5.6.x and I may even test on 5.6.2.  I will accept patches to maintain
       compatibility for such older Perls, but you may need to fix it on 5.6.x / 5.8.0 and send
       me a patch.

       Not tested on VMS 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.

SUPPORT

       Bugs should be reported via the GitHub issue tracker

       <https://github.com/plicease/File-Which/issues>

       For other issues, contact the maintainer.

AUTHORS

       •   Per Einar Ellefsen <pereinar@cpan.org>

       •   Adam Kennedy <adamk@cpan.org>

       •   Graham Ollis <plicease@cpan.org>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2002 by Per Einar Ellefsen <pereinar@cpan.org>.

       This is free software; you can redistribute it and/or modify it under the same terms as
       the Perl 5 programming language system itself.