1File::Which(3)        User Contributed Perl Documentation       File::Which(3)
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NAME

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

9       version 1.22
10

SYNOPSIS

12        use File::Which;                  # exports which()
13        use File::Which qw(which where);  # exports which() and where()
14
15        my $exe_path = which 'perldoc';
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17        my @paths = where 'perl';
18        # Or
19        my @paths = which 'perl'; # an array forces search for all of them
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DESCRIPTION

22       File::Which finds the full or relative paths to executable programs on
23       the system.  This is normally the function of "which" utility.  "which"
24       is typically implemented as either a program or a built in shell
25       command.  On some platforms, such as Microsoft Windows it is not
26       provided as part of the core operating system.  This module provides a
27       consistent API to this functionality regardless of the underlying
28       platform.
29
30       The focus of this module is correctness and portability.  As a
31       consequence platforms where the current directory is implicitly part of
32       the search path such as Microsoft Windows will find executables in the
33       current directory, whereas on platforms such as UNIX where this is not
34       the case executables in the current directory will only be found if the
35       current directory is explicitly added to the path.
36
37       If you need a portable "which" on the command line in an environment
38       that does not provide it, install App::pwhich which provides a command
39       line interface to this API.
40
41   Implementations
42       File::Which searches the directories of the user's "PATH" (the current
43       implementation uses File::Spec#path to determine the correct "PATH"),
44       looking for executable files having the name specified as a parameter
45       to "which". Under Win32 systems, which do not have a notion of directly
46       executable files, but uses special extensions such as ".exe" and ".bat"
47       to identify them, "File::Which" takes extra steps to assure that you
48       will find the correct file (so for example, you might be searching for
49       "perl", it'll try perl.exe, perl.bat, etc.)
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51       Linux, *BSD and other UNIXes
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53       There should not be any surprises here.  The current directory will not
54       be searched unless it is explicitly added to the path.
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56       Modern Windows (including NT, XP, Vista, 7, 8, 10 etc)
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58       Windows NT has a special environment variable called "PATHEXT", which
59       is used by the shell to look for executable files. Usually, it will
60       contain a list in the form ".EXE;.BAT;.COM;.JS;.VBS" etc. If
61       "File::Which" finds such an environment variable, it parses the list
62       and uses it as the different extensions.
63
64       Cygwin
65
66       Cygwin provides a Unix-like environment for Microsoft Windows users.
67       In most ways it works like other Unix and Unix-like environments, but
68       in a few key aspects it works like Windows.  As with other Unix
69       environments, the current directory is not included in the search
70       unless it is explicitly included in the search path.  Like on Windows,
71       files with ".EXE" or <.BAT> extensions will be discovered even if they
72       are not part of the query.  ".COM" or extensions specified using the
73       "PATHEXT" environment variable will NOT be discovered without the fully
74       qualified name, however.
75
76       Windows 95, 98, ME, MS-DOS, OS/2
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78       This set of operating systems don't have the "PATHEXT" variable, and
79       usually you will find executable files there with the extensions
80       ".exe", ".bat" and (less likely) ".com". "File::Which" uses this
81       hardcoded list if it's running under Win32 but does not find a
82       "PATHEXT" variable.
83
84       As of 2015 none of these platforms are tested frequently (or perhaps
85       ever), but the current maintainer is determined not to intentionally
86       remove support for older operating systems.
87
88       VMS
89
90       Same case as Windows 9x: uses ".exe" and ".com" (in that order).
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92       As of 2015 the current maintainer does not test on VMS, and is in fact
93       not certain it has ever been tested on VMS.  If this platform is
94       important to you and you can help me verify and or support it on that
95       platform please contact me.
96

FUNCTIONS

98   which
99        my $path = which $short_exe_name;
100        my @paths = which $short_exe_name;
101
102       Exported by default.
103
104       $short_exe_name is the name used in the shell to call the program (for
105       example, "perl").
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107       If it finds an executable with the name you specified, "which()" will
108       return the absolute path leading to this executable (for example,
109       /usr/bin/perl or C:\Perl\Bin\perl.exe).
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111       If it does not find the executable, it returns "undef".
112
113       If "which()" is called in list context, it will return all the matches.
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115   where
116        my @paths = where $short_exe_name;
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118       Not exported by default.
119
120       Same as "which" in array context. Same as the "where" utility, will
121       return an array containing all the path names matching $short_exe_name.
122

CAVEATS

124       This module has no non-core requirements for Perl 5.6.2 and better.
125
126       This module is fully supported back to Perl 5.8.1.  It may work on
127       5.8.0.  It should work on Perl 5.6.x and I may even test on 5.6.2.  I
128       will accept patches to maintain compatibility for such older Perls, but
129       you may need to fix it on 5.6.x / 5.8.0 and send me a patch.
130
131       Not tested on VMS although there is platform specific code for those.
132       Anyone who haves a second would be very kind to send me a report of how
133       it went.
134

SUPPORT

136       Bugs should be reported via the GitHub issue tracker
137
138       <https://github.com/plicease/File-Which/issues>
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140       For other issues, contact the maintainer.
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SEE ALSO

143       pwhich, App::pwhich
144           Command line interface to this module.
145
146       IPC::Cmd
147           Comes with a "can_run" function with slightly different semantics
148           that the traditional UNIX where.  It will find executables in the
149           current directory, even though the current directory is not
150           searched for by default on Unix.
151
152       Devel::CheckBin
153           This module purports to "check that a command is available", but
154           does not provide any documentation on how you might use it.
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AUTHORS

157       ·   Per Einar Ellefsen <pereinar@cpan.org>
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159       ·   Adam Kennedy <adamk@cpan.org>
160
161       ·   Graham Ollis <plicease@cpan.org>
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164       This software is copyright (c) 2002 by Per Einar Ellefsen
165       <pereinar@cpan.org>.
166
167       This is free software; you can redistribute it and/or modify it under
168       the same terms as the Perl 5 programming language system itself.
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172perl v5.28.0                      2017-09-08                    File::Which(3)
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