1Shell::Guess(3) User Contributed Perl Documentation Shell::Guess(3)
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6 Shell::Guess - Make an educated guess about the shell in use
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9 version 0.09
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12 guessing shell which called the Perl script:
13 use Shell::Guess;
15 my $shell = Shell::Guess->running_shell;
16 if($shell->is_c) {
17 print "setenv FOO bar\n";
18 } elsif($shell->is_bourne) {
19 print "export FOO=bar\n";
20 }
21 guessing the current user's login shell:
23 use Shell::Guess;
25 my $shell = Shell::Guess->login_shell;
26 print $shell->name, "\n";
27 guessing an arbitrary user's login shell:
29 use Shell::Guess;
31 my $shell = Shell::Guess->login_shell('bob');
32 print $shell->name, "\n";
33
35 Shell::Guess makes a reasonably aggressive attempt to determine the
36 shell being employed by the user, either the shell that executed the
37 perl script directly (the "running" shell), or the users' login shell
38 (the "login" shell). It does this by a variety of means available to
39 it, depending on the platform that it is running on.
40 • getpwent
42 On UNIXy systems with getpwent, that can be used to determine the
44 login shell.
45 • dscl
47 Under Mac OS X getpwent will typically not provide any useful
49 information, so the dscl command is used instead.
50 • proc file systems
52 On UNIXy systems with a proc filesystems (such as Linux),
54 Shell::Guess will attempt to use that to determine the running
55 shell.
56 • ps
58 On UNIXy systems without a proc filesystem, Shell::Guess will use
60 the ps command to determine the running shell.
61 • Win32::Getppid and Win32::Process::List
63 On Windows if these modules are installed they will be used to
65 determine the running shell. This method can differentiate between
66 PowerShell, "command.com" and "cmd.exe".
67 • ComSpec
69 If the above method is inconclusive, the ComSpec environment
71 variable will be consulted to differentiate between "command.com"
72 or "cmd.exe" (PowerShell cannot be detected in this manner).
73 • reasonable defaults
75 If the running or login shell cannot be otherwise determined, a
77 reasonable default for your platform will be used as a fallback.
78 Under OpenVMS this is dcl, Windows 95/98 and MS-DOS this is
79 command.com and Windows NT/2000/XP/Vista/7 this is cmd.exe. UNIXy
80 platforms fallback to bourne shell.
81 The intended use of this module is to enable a Perl developer to write
83 a script that generates shell configurations for the calling shell so
84 they can be imported back into the calling shell using "eval" and
85 backticks or "source". For example, if your script looks like this:
86 #!/usr/bin/perl
88 use Shell::Guess;
89 my $shell = Shell::Guess->running_shell;
90 if($shell->is_bourne) {
91 print "export FOO=bar\n";
92 } else($shell->is_c) {
93 print "setenv FOO bar\n";
94 } else {
95 die "I don't support ", $shell->name, " shell";
96 }
97 You can then import FOO into your bash or c shell like this:
99 % eval `perl script.pl`
101 or, you can write the output to a configuration file and source it:
103 % perl script.pl > foo.sh
105 % source foo.sh
106 Shell::Config::Generate provides a portable interface for generating
108 such shell configurations, and is designed to work with this module.
109
111 These class methods return an instance of Shell::Guess, which can then
112 be interrogated by the instance methods in the next section below.
113 running_shell
115 my $shell = Shell::Guess->running_shell;
116 Returns an instance of Shell::Guess based on the shell which directly
118 started the current Perl script. If the running shell cannot be
119 determined, it will return the login shell.
120 login_shell
122 my $shell = Shell::Guess->login_shell;
123 my $shell = Shell::Guess->login_shell( $username )
124 Returns an instance of Shell::Guess for the given user. If no username
126 is specified then the current user will be used. If no shell can be
127 guessed then a reasonable fallback will be chosen based on your
128 platform.
129 bash_shell
131 my $shell = Shell::Guess->bash_shell;
132 Returns an instance of Shell::Guess for bash.
134 The following instance methods will return:
136 • $shell->name = bash
138 • $shell->is_bash = 1
140 • $shell->is_bourne = 1
142 • $shell->is_unix = 1
144 • $shell->default_location = /bin/bash
146 All other instance methods will return false
148 bourne_shell
150 my $shell = Shell::Guess->bourne_shell;
151 Returns an instance of Shell::Guess for the bourne shell.
153 The following instance methods will return:
155 • $shell->name = bourne
157 • $shell->is_bourne = 1
159 • $shell->is_unix = 1
161 • $shell->default_location = /bin/sh
163 All other instance methods will return false
165 c_shell
167 my $shell = Shell::Guess->c_shell;
168 Returns an instance of Shell::Guess for c shell.
170 The following instance methods will return:
172 • $shell->name = c
174 • $shell->is_c = 1
176 • $shell->is_unix = 1
178 • $shell->default_location = /bin/csh
180 All other instance methods will return false
182 cmd_shell
184 my $shell = Shell::Guess->cmd_shell;
185 Returns an instance of Shell::Guess for the Windows NT cmd shell
187 (cmd.exe).
188 The following instance methods will return:
190 • $shell->name = cmd
192 • $shell->is_cmd = 1
194 • $shell->is_win32 = 1
196 • $shell->default_location = C:\Windows\system32\cmd.exe
198 All other instance methods will return false
200 command_shell
202 my $shell = Shell::Guess->command_shell;
203 Returns an instance of Shell::Guess for the Windows 95 command shell
205 (command.com).
206 The following instance methods will return:
208 • $shell->name = command
210 • $shell->is_command = 1
212 • $shell->is_win32 = 1
214 • $shell->default_location = C:\Windows\system32\command.com
216 All other instance methods will return false
218 dcl_shell
220 my $shell = Shell::Guess->dcl_shell;
221 Returns an instance of Shell::Guess for the OpenVMS dcl shell.
223 The following instance methods will return:
225 • $shell->name = dcl
227 • $shell->is_dcl = 1
229 • $shell->is_vms = 1
231 All other instance methods will return false
233 fish_shell
235 my $shell = Shell::Guess->fish_shell;
236 Returns an instance of Shell::Guess for the fish shell.
238 The following instance methods will return:
240 • $shell->name = fish
242 • $shell->is_fish = 1
244 • $shell->is_unix = 1
246 korn_shell
248 my $shell = Shell::Guess->korn_shell;
249 Returns an instance of Shell::Guess for the korn shell.
251 The following instance methods will return:
253 • $shell->name = korn
255 • $shell->is_korn = 1
257 • $shell->is_bourne = 1
259 • $shell->is_unix = 1
261 • $shell->default_location = /bin/ksh
263 All other instance methods will return false
265 power_shell
267 my $shell = Shell::Guess->power_shell;
268 Returns an instance of Shell::Guess for Microsoft PowerShell (either
270 for Windows "powershell.exe" or Unix "pwsh").
271 The following instance methods will return:
273 • $shell->name = power
275 • $shell->is_power = 1
277 • $shell->is_win32 = 1
279 All other instance methods will return false
281 tc_shell
283 my $shell = Shell::Guess->tc_shell;
284 Returns an instance of Shell::Guess for tcsh.
286 The following instance methods will return:
288 • $shell->name = tc
290 • $shell->is_tc = 1
292 • $shell->is_c = 1
294 • $shell->is_unix = 1
296 • $shell->default_location = /bin/tcsh
298 All other instance methods will return false
300 z_shell
302 my $shell = Shell::Guess->z_shell
303 Returns an instance of Shell::Guess for zsh.
305 The following instance methods will return:
307 • $shell->name = z
309 • $shell->is_z = 1
311 • $shell->is_bourne = 1
313 • $shell->is_unix = 1
315 • $shell->default_location = /bin/zsh
317 All other instance methods will return false
319
321 The normal way to call these is by calling them on the result of either
322 running_shell or login_shell, but they can also be called as class
323 methods, in which case the currently running shell will be used, so
324 Shell::Guess->is_bourne
326 is the same as
328 Shell::Guess->running_shell->is_bourne
330 is_bash
332 my $bool = $shell->is_bash;
333 Returns true if the shell is bash.
335 is_bourne
337 my $bool = $shell->is_bourne;
338 Returns true if the shell is the bourne shell, or a shell which
340 supports bourne syntax (e.g. bash or korn).
341 is_c
343 my $bool = $shell->is_c;
344 Returns true if the shell is csh, or a shell which supports csh syntax
346 (e.g. tcsh).
347 is_cmd
349 my $bool = $shell->is_cmd;
350 Returns true if the shell is the Windows command.com shell.
352 is_command
354 my $bool = $shell->is_command;
355 Returns true if the shell is the Windows cmd.com shell.
357 is_dcl
359 my $bool = $shell->is_dcl;
360 Returns true if the shell is the OpenVMS dcl shell.
362 is_fish
364 my $bool = $shell->is_fish;
365 Returns true if the shell is Fish shell.
367 is_korn
369 my $bool = $shell->is_korn;
370 Returns true if the shell is the korn shell.
372 is_power
374 my $bool = $shell->is_power;
375 Returns true if the shell is Windows PowerShell.
377 is_tc
379 my $bool = $shell->is_tc;
380 Returns true if the shell is tcsh.
382 is_unix
384 my $bool = $shell->is_unix;
385 Returns true if the shell is traditionally a UNIX shell (e.g. bourne,
387 bash, korn)
388 is_vms
390 my $bool = $shell->is_vms;
391 Returns true if the shell is traditionally an OpenVMS shell (e.g. dcl)
393 is_win32
395 my $bool = $shell->is_win32;
396 Returns true if the shell is traditionally a Windows shell
398 (command.com, cmd.exe, powershell.exe, pwsh)
399 is_z
401 my $bool = $shell->is_z;
402 Returns true if the shell is zsh
404 name
406 my $name = $shell->name;
407 Returns the name of the shell.
409 default_location
411 my $location = $shell->default_location;
412 The usual location for this shell, for example /bin/sh for bourne shell
414 and /bin/csh for c shell. May not be defined for all shells.
415
417 Shell::Guess shouldn't ever die or crash, instead it will attempt to
418 make a guess or use a fallback about either the login or running shell
419 even on unsupported operating systems. The fallback is the most common
420 shell on the particular platform that you are using, so on UNIXy
421 platforms the fallback is bourne, and on OpenVMS the fallback is dcl.
422 These are the operating systems that have been tested in development
424 and are most likely to guess reliably.
425 • Linux
427 • Cygwin
429 • FreeBSD
431 • Mac OS X
433 • Windows (Strawberry Perl)
435 • Solaris (x86)
437 • MS-DOS (djgpp)
439 • OpenVMS
441 Always detected as dcl (a more nuanced view of OpenVMS is probably
443 possible, patches welcome).
444 UNIXy platforms without a proc filesystem will use Unix::Process if
446 installed, which will execute ps to determine the running shell.
447 It is pretty easy to fool the ->running_shell method by using fork, or
449 if your Perl script is not otherwise being directly executed by the
450 shell.
451 Patches are welcome to make other platforms work more reliably.
453
455 Author: Graham Ollis <plicease@cpan.org>
456 Contributors:
458 Buddy Burden (BAREFOOT)
460 Julien Fiegehenn (SIMBABQUE)
462
464 This software is copyright (c) 2012 by Graham Ollis.
465 This is free software; you can redistribute it and/or modify it under
467 the same terms as the Perl 5 programming language system itself.
468perl v5.38.0 2023-07-21 Shell::Guess(3)