File::Which - phpMan

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

VERSION
    version 1.23

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 ME, 98, 95, 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. Similar to the "where" csh built-in
    command or "which -a" command for platforms that support the "-a"
    option. Will return an array containing all the path names matching
    $short_exe_name.

GLOBALS
  $IMPLICIT_CURRENT_DIR
    True if the current directory is included in the search implicitly on
    whatever platform you are using. Normally the default is reasonable, but
    on Windows the current directory is included implicitly for older shells
    like "cmd.exe" and "command.com", but not for newer shells like
    PowerShell. If you overrule this default, you should ALWAYS localize the
    variable to the tightest scope possible, since setting this variable
    from a module can affect other modules. Thus on Windows you can get the
    correct result if the user is running either "cmd.exe" or PowerShell on
    Windows you can do this:

     use File::Which qw( which );
     use Shell::Guess;

     my $path = do {
       my $is_power = Shell::Guess->running_shell->is_power;
       local $File::Which::IMPLICIT_CURRENT_DIR = !$is_power;
       which 'foo';
     };

    For a variety of reasons it is difficult to accurately compute the shell
    that a user is using, but Shell::Guess makes a reasonable effort.

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.

SEE ALSO
    pwhich, App::pwhich
        Command line interface to this module.

    IPC::Cmd
        This module provides (among other things) a "can_run" function,
        which is similar to "which". It is a much heavier module since it
        does a lot more, and if you use "can_run" it pulls in
        ExtUtils::MakeMaker. This combination may be overkill for
        applications which do not need IPC::Cmd's complicated interface for
        running programs, or do not need the memory overhead required for
        installing Perl modules.

        At least some older versions will find executables in the current
        directory, even if the current directory is not in the search path
        (which is the default on modern Unix).

        "can_run" converts directory path name to the 8.3 version on Windows
        using "Win32::GetShortPathName" in some cases. This is frequently
        useful for tools that just need to run something using "system" in
        scalar mode, but may be inconvenient for tools like App::pwhich
        where user readability is a premium. Relying on
        "Win32::GetShortPathName" to produce filenames without spaces is
        problematic, as 8.3 filenames can be turned off with tweaks to the
        registry (see
        <https://technet.microsoft.com/en-us/library/cc959352.aspx>).

    Devel::CheckBin
        This module purports to "check that a command is available", but
        does not provide any documentation on how you might use it.

AUTHORS
    *   Per Einar Ellefsen <pereinar AT cpan.org>

    *   Adam Kennedy <adamk AT cpan.org>

    *   Graham Ollis <plicease AT cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2002 by Per Einar Ellefsen
    <pereinar AT 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.