File::Which(3pm)

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

6       File::Which - Portable implementation of the `which' utility
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SYNOPSIS

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

19       "File::Which" was created to be able to get the paths to executable
20       programs on systems under which the `which' program wasn't implemented
21       in the shell.
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23       "File::Which" searches the directories of the user's "PATH" (as
24       returned by "File::Spec->path()"), looking for executable files having
25       the name specified as a parameter to "which()". Under Win32 systems,
26       which do not have a notion of directly executable files, but uses spe‐
27       cial extensions such as ".exe" and ".bat" to identify them,
28       "File::Which" takes extra steps to assure that you will find the cor‐
29       rect file (so for example, you might be searching for "perl", it'll try
30       "perl.exe", "perl.bat", etc.)
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Steps Used on Win32, DOS, OS2 and VMS

33       Windows NT
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35       Windows NT has a special environment variable called "PATHEXT", which
36       is used by the shell to look for executable files. Usually, it will
37       contain a list in the form ".EXE;.BAT;.COM;.JS;.VBS" etc. If
38       "File::Which" finds such an environment variable, it parses the list
39       and uses it as the different extensions.
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41       Windows 9x and other ancient Win/DOS/OS2
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43       This set of operating systems don't have the "PATHEXT" variable, and
44       usually you will find executable files there with the extensions
45       ".exe", ".bat" and (less likely) ".com". "File::Which" uses this hard‐
46       coded list if it's running under Win32 but does not find a "PATHEXT"
47       variable.
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49       VMS
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51       Same case as Windows 9x: uses ".exe" and ".com" (in that order).
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Functions

54       which($short_exe_name)
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56       Exported by default.
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58       $short_exe_name is the name used in the shell to call the program (for
59       example, "perl").
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61       If it finds an executable with the name you specified, "which()" will
62       return the absolute path leading to this executable (for example,
63       "/usr/bin/perl" or "C:\Perl\Bin\perl.exe").
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65       If it does not find the executable, it returns "undef".
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67       If "which()" is called in list context, it will return all the matches.
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69       where($short_exe_name)
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71       Not exported by default.
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73       Same as "which($short_exe_name)" in array context. Same as the `where'
74       utility, will return an array containing all the path names matching
75       $short_exe_name.
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Bugs and Caveats

78       Not tested on VMS or MacOS, although there is platform specific code
79       for those. Anyone who haves a second would be very kind to send me a
80       report of how it went.
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82       File::Spec adds the current directory to the front of PATH if on Win32,
83       VMS or MacOS. I have no knowledge of those so don't know if the current
84       directory is searced first or not. Could someone please tell me?
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Author

87       Per Einar Ellefsen, <per.einar (at) skynet.be>
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89       Originated in modperl-2.0/lib/Apache/Build.pm. Changed for use in Doc‐
90       Set (for the mod_perl site) and Win32-awareness by me, with slight mod‐
91       ifications by Stas Bekman, then extracted to create "File::Which".
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93       Version 0.04 had some significant platform-related changes, taken from
94       the Perl Power Tools `which' implementation by Abigail with enhance‐
95       ments from Peter Prymmer. See http://www.perl.com/lan‐
96       guage/ppt/src/which/index.html for more information.
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License

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