Shell::Guess(3)

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

VERSION
version 0.09

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 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.