NAME

    Shell::Guess - Make an educated guess about the shell in use

VERSION

    version 0.10

SYNOPSIS

    guessing shell which called the Perl script:

     use Shell::Guess;
     my $shell = Shell::Guess->running_shell;
     if($shell->is_c) {
       print "setenv FOO bar\n";
     } elsif($shell->is_bourne) {
       print "export FOO=bar\n";
     }

    guessing the current user's login shell:

     use Shell::Guess;
     my $shell = Shell::Guess->login_shell;
     print $shell->name, "\n";

    guessing an arbitrary user's login shell:

     use Shell::Guess;
     my $shell = Shell::Guess->login_shell('bob');
     print $shell->name, "\n";

DESCRIPTION

    Shell::Guess makes a reasonably aggressive attempt to determine the
    shell being employed by the user, either the shell that executed the
    perl script directly (the "running" shell), or the users' login shell
    (the "login" shell). It does this by a variety of means available to
    it, depending on the platform that it is running on.

      * getpwent

      On UNIXy systems with getpwent, that can be used to determine the
      login shell.

      * dscl

      Under Mac OS X getpwent will typically not provide any useful
      information, so the dscl command is used instead.

      * proc file systems

      On UNIXy systems with a proc filesystems (such as Linux),
      Shell::Guess will attempt to use that to determine the running shell.

      * ps

      On UNIXy systems without a proc filesystem, Shell::Guess will use the
      ps command to determine the running shell.

      * Win32::Getppid and Win32::Process::List

      On Windows if these modules are installed they will be used to
      determine the running shell. This method can differentiate between
      PowerShell, command.com and cmd.exe.

      * ComSpec

      If the above method is inconclusive, the ComSpec environment variable
      will be consulted to differentiate between command.com or cmd.exe
      (PowerShell cannot be detected in this manner).

      * reasonable defaults

      If the running or login shell cannot be otherwise determined, a
      reasonable default for your platform will be used as a fallback.
      Under OpenVMS this is dcl, Windows 95/98 and MS-DOS this is
      command.com and Windows NT/2000/XP/Vista/7 this is cmd.exe. UNIXy
      platforms fallback to bourne shell.

    The intended use of this module is to enable a Perl developer to write
    a script that generates shell configurations for the calling shell so
    they can be imported back into the calling shell using eval and
    backticks or source. For example, if your script looks like this:

     #!/usr/bin/perl
     use Shell::Guess;
     my $shell = Shell::Guess->running_shell;
     if($shell->is_bourne) {
       print "export FOO=bar\n";
     } else($shell->is_c) {
       print "setenv FOO bar\n";
     } else {
       die "I don't support ", $shell->name, " shell";
     }

    You can then import FOO into your bash or c shell like this:

     % eval `perl script.pl`

    or, you can write the output to a configuration file and source it:

     % perl script.pl > foo.sh
     % source foo.sh

    Shell::Config::Generate provides a portable interface for generating
    such shell configurations, and is designed to work with this module.

CLASS METHODS

    These class methods return an instance of Shell::Guess, which can then
    be interrogated by the instance methods in the next section below.

 running_shell

     my $shell = Shell::Guess->running_shell;

    Returns an instance of Shell::Guess based on the shell which directly
    started the current Perl script. If the running shell cannot be
    determined, it will return the login shell.

 login_shell

     my $shell = Shell::Guess->login_shell;
     my $shell = Shell::Guess->login_shell( $username )

    Returns an instance of Shell::Guess for the given user. If no username
    is specified then the current user will be used. If no shell can be
    guessed then a reasonable fallback will be chosen based on your
    platform.

 bash_shell

     my $shell = Shell::Guess->bash_shell;

    Returns an instance of Shell::Guess for bash.

    The following instance methods will return:

      * $shell->name = bash

      * $shell->is_bash = 1

      * $shell->is_bourne = 1

      * $shell->is_unix = 1

      * $shell->default_location = /bin/bash

    All other instance methods will return false

 bourne_shell

     my $shell = Shell::Guess->bourne_shell;

    Returns an instance of Shell::Guess for the bourne shell.

    The following instance methods will return:

      * $shell->name = bourne

      * $shell->is_bourne = 1

      * $shell->is_unix = 1

      * $shell->default_location = /bin/sh

    All other instance methods will return false

 c_shell

     my $shell = Shell::Guess->c_shell;

    Returns an instance of Shell::Guess for c shell.

    The following instance methods will return:

      * $shell->name = c

      * $shell->is_c = 1

      * $shell->is_unix = 1

      * $shell->default_location = /bin/csh

    All other instance methods will return false

 cmd_shell

     my $shell = Shell::Guess->cmd_shell;

    Returns an instance of Shell::Guess for the Windows NT cmd shell
    (cmd.exe).

    The following instance methods will return:

      * $shell->name = cmd

      * $shell->is_cmd = 1

      * $shell->is_win32 = 1

      * $shell->default_location = C:\Windows\system32\cmd.exe

    All other instance methods will return false

 command_shell

     my $shell = Shell::Guess->command_shell;

    Returns an instance of Shell::Guess for the Windows 95 command shell
    (command.com).

    The following instance methods will return:

      * $shell->name = command

      * $shell->is_command = 1

      * $shell->is_win32 = 1

      * $shell->default_location = C:\Windows\system32\command.com

    All other instance methods will return false

 dcl_shell

     my $shell = Shell::Guess->dcl_shell;

    Returns an instance of Shell::Guess for the OpenVMS dcl shell.

    The following instance methods will return:

      * $shell->name = dcl

      * $shell->is_dcl = 1

      * $shell->is_vms = 1

    All other instance methods will return false

 fish_shell

     my $shell = Shell::Guess->fish_shell;

    Returns an instance of Shell::Guess for the fish shell.

    The following instance methods will return:

      * $shell->name = fish

      * $shell->is_fish = 1

      * $shell->is_unix = 1

 korn_shell

     my $shell = Shell::Guess->korn_shell;

    Returns an instance of Shell::Guess for the korn shell.

    The following instance methods will return:

      * $shell->name = korn

      * $shell->is_korn = 1

      * $shell->is_bourne = 1

      * $shell->is_unix = 1

      * $shell->default_location = /bin/ksh

    All other instance methods will return false

 power_shell

      my $shell = Shell::Guess->power_shell;

    Returns an instance of Shell::Guess for Microsoft PowerShell (either
    for Windows powershell.exe or Unix pwsh).

    The following instance methods will return:

      * $shell->name = power

      * $shell->is_power = 1

      * $shell->is_win32 = 1

    All other instance methods will return false

 tc_shell

     my $shell = Shell::Guess->tc_shell;

    Returns an instance of Shell::Guess for tcsh.

    The following instance methods will return:

      * $shell->name = tc

      * $shell->is_tc = 1

      * $shell->is_c = 1

      * $shell->is_unix = 1

      * $shell->default_location = /bin/tcsh

    All other instance methods will return false

 z_shell

     my $shell = Shell::Guess->z_shell

    Returns an instance of Shell::Guess for zsh.

    The following instance methods will return:

      * $shell->name = z

      * $shell->is_z = 1

      * $shell->is_bourne = 1

      * $shell->is_unix = 1

      * $shell->default_location = /bin/zsh

    All other instance methods will return false

INSTANCE METHODS

    The normal way to call these is by calling them on the result of either
    running_shell or login_shell, but they can also be called as class
    methods, in which case the currently running shell will be used, so

     Shell::Guess->is_bourne

    is the same as

     Shell::Guess->running_shell->is_bourne

 is_bash

     my $bool = $shell->is_bash;

    Returns true if the shell is bash.

 is_bourne

     my $bool = $shell->is_bourne;

    Returns true if the shell is the bourne shell, or a shell which
    supports bourne syntax (e.g. bash or korn).

 is_c

     my $bool = $shell->is_c;

    Returns true if the shell is csh, or a shell which supports csh syntax
    (e.g. tcsh).

 is_cmd

     my $bool = $shell->is_cmd;

    Returns true if the shell is the Windows command.com shell.

 is_command

     my $bool = $shell->is_command;

    Returns true if the shell is the Windows cmd.com shell.

 is_dcl

     my $bool = $shell->is_dcl;

    Returns true if the shell is the OpenVMS dcl shell.

 is_fish

     my $bool = $shell->is_fish;

    Returns true if the shell is Fish shell.

 is_korn

     my $bool = $shell->is_korn;

    Returns true if the shell is the korn shell.

 is_power

     my $bool = $shell->is_power;

    Returns true if the shell is Windows PowerShell.

 is_tc

     my $bool = $shell->is_tc;

    Returns true if the shell is tcsh.

 is_unix

     my $bool = $shell->is_unix;

    Returns true if the shell is traditionally a UNIX shell (e.g. bourne,
    bash, korn)

 is_vms

     my $bool = $shell->is_vms;

    Returns true if the shell is traditionally an OpenVMS shell (e.g. dcl)

 is_win32

     my $bool = $shell->is_win32;

    Returns true if the shell is traditionally a Windows shell
    (command.com, cmd.exe, powershell.exe, pwsh)

 is_z

     my $bool = $shell->is_z;

    Returns true if the shell is zsh

 name

     my $name = $shell->name;

    Returns the name of the shell.

 default_location

     my $location = $shell->default_location;

    The usual location for this shell, for example /bin/sh for bourne shell
    and /bin/csh for c shell. May not be defined for all shells.

CAVEATS

    Shell::Guess shouldn't ever die or crash, instead it will attempt to
    make a guess or use a fallback about either the login or running shell
    even on unsupported operating systems. The fallback is the most common
    shell on the particular platform that you are using, so on UNIXy
    platforms the fallback is bourne, and on OpenVMS the fallback is dcl.

    These are the operating systems that have been tested in development
    and are most likely to guess reliably.

      * Linux

      * Cygwin

      * FreeBSD

      * Mac OS X

      * Windows (Strawberry Perl)

      * Solaris (x86)

      * MS-DOS (djgpp)

      * OpenVMS

      Always detected as dcl (a more nuanced view of OpenVMS is probably
      possible, patches welcome).

    UNIXy platforms without a proc filesystem will use Unix::Process if
    installed, which will execute ps to determine the running shell.

    It is pretty easy to fool the ->running_shell method by using fork, or
    if your Perl script is not otherwise being directly executed by the
    shell.

    Patches are welcome to make other platforms work more reliably.

AUTHOR

    Author: Graham Ollis <plicease@cpan.org>

    Contributors:

    Buddy Burden (BAREFOOT)

    Julien Fiegehenn (SIMBABQUE)

COPYRIGHT AND LICENSE

    This software is copyright (c) 2012-2023 by Graham Ollis.

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