From: pjb@informatimago.com (Pascal J. Bourguignon)
To: help-gnu-emacs@gnu.org
Subject: Re: system-command-exists-p
Date: Mon, 07 Dec 2009 14:44:00 +0100 [thread overview]
Message-ID: <87vdgiew67.fsf@galatea.local> (raw)
In-Reply-To: mailman.12419.1260187409.2239.help-gnu-emacs@gnu.org
Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
> Pascal J. Bourguignon wrote:
>> Andreas Roehler <andreas.roehler@online.de> writes:
>>
>>> Hi,
>>>
>>> needed a check if a command exists on system.
>>> Employed the following:
>>>
>>> (defun system-command-exists-p (command)
>>> "Return t if COMMAND is available on system. "
>>> (let* ((cmd (format "type %s" command)))
>>> (eq 0 (shell-command cmd))))
>>>
>>> Any comments/suggestions?
>>
>> Use %S or (shell-quote-argument command).
>>
>> type is a built-in command specific to the sh familly of shells.
>> Perhaps it would be a good idea to explicitely call up sh?
>
>
>>
>> It may be useful to return the path of the command:
>>
>> (defun system-command-exists-p (command)
>> "Return t if COMMAND is available on system. "
>> (let* ((cmd (format "/bin/sh -c 'type %s'"
>> (shell-quote-argument command))))
>> (when (eql 0 (shell-command cmd))
>> (let ((result (shell-command-to-string cmd)))
>> (if (string-match "^.* is \\(.*\\)\n$"result)
>> (match-string 1 result)
>> result)))))
>>
>> (mapcar (function system-command-exists-p)
>> '("cat" "type" "foo"))
>> --> ("/bin/cat" "a shell builtin" nil)
>>
>>
>>
>
> Thanks a lot.
>
> Concerning the precise kind-of-"shell"-question, I'm not sure.
> Case is to write a check for pack-unpack functions.
>
> Presently dired-do-compress uses a hard-encoded "gzip", replaced here by
> a choice so far.
>
> Then testing all compressing/uncompressing possibilities, it turns out some might not be installed.
>
> type uncompress =>
> uncompress is /usr/bin/uncompress
> type compress =>
> bash: type: compress: not found
>
> Test should not fail, if these programms are not installed, rather give a message.
> So far the issue here.
>
> Think the shell-in-use should not matter, resp. will be selected already.
>
> What about to write:
>
> (cmd (format (concat (getenv "SHELL") " -c 'type %s'")
My point was that SHELL might be csh or tcsh which don't have a type
command built-in, or even scsh or clash (clisp) who don't even use the
same syntax! Or yet something else.
So you can just make the assumption that SHELL is a sh-compatible
shell, and go ahead, or try to run sh yourself.
After all, people who use csh or tcsh just deserve what they get, and
people using exotic shells are expected to know what they're doing ;-)
--
__Pascal Bourguignon__
next prev parent reply other threads:[~2009-12-07 13:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.12411.1260170302.2239.help-gnu-emacs@gnu.org>
2009-12-07 10:13 ` system-command-exists-p Pascal J. Bourguignon
2009-12-07 12:02 ` system-command-exists-p Andreas Röhler
[not found] ` <mailman.12419.1260187409.2239.help-gnu-emacs@gnu.org>
2009-12-07 13:44 ` Pascal J. Bourguignon [this message]
2009-12-07 16:22 ` system-command-exists-p Andreas Politz
2009-12-07 16:00 ` system-command-exists-p Stefan Monnier
2009-12-07 18:57 ` system-command-exists-p Andreas Röhler
2009-12-07 7:17 system-command-exists-p Andreas Roehler
2009-12-07 16:30 ` system-command-exists-p Lennart Borgman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87vdgiew67.fsf@galatea.local \
--to=pjb@informatimago.com \
--cc=help-gnu-emacs@gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).