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

VERSION
    version 0.01

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::Process::Info 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.

  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.

  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.

  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

  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

  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

  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

  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

  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

  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

  Shell::Guess->power_shell
    Returns an instance of Shell::Guess for Windows PowerShell.

    The following instance methods will return:

    *   $shell->name = power

    *   $shell->is_power = 1

    *   $shell->is_win32 = 1

    All other instance methods will return false

  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

  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

  $shell->is_bash
    Returns true if the shell is bash.

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

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

  $shell->is_cmd
    Returns true if the shell is the Windows command.com shell.

  $shell->is_command
    Returns true if the shell is the Windows cmd.com shell.

  $shell->is_dcl
    Returns true if the shell is the OpenVMS dcl shell.

  $shell->is_korn
    Returns true if the shell is the korn shell.

  $shell->is_power
    Returns true if the shell is Windows PowerShell.

  $shell->is_tc
    Returns true if the shell is tcsh.

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

  $shell->is_vms
    Returns true if the shell is traditionally an OpenVMS shell (e.g. dcl)

  $shell->is_win32
    Returns true if the shell is traditionally a Windows shell (command.com,
    cmd.exe)

  $shell->is_z
    Returns true if the shell is zsh

  $shell->name
    Returns the name of the shell.

  $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)

    *   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
    Graham Ollis <plicease@cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2012 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.

