[OS X TeX] can't find files in /usr/local/tetex/bin/
Stefan Walsen
stefan at walsen.net
Fri Apr 9 13:04:16 CEST 2004
Justin Walker wrote:
> On Apr 8, 2004, at 17:06, Stefan Walsen wrote:
>> That depends on several things:
>> If the first line is "#!/bin/bash", it'll be run by bash and
>> everything will work fine.
> That is true; what I was pointing out is that you (or, at least, I)
> don't know that, within the environment where that shell script is
> executing, the variable SHELL will be set to '/bin/bash', or perhaps,
> the environment inherits the setting of SHELL from the shell that
> invoked the shell script in the first place.
Ah, OK. That's definitely not what I thought we were talking about :)
The value of $SHELL is indeed inherited from the parent process.
So when somewhere SHELL is set to '/bin/bash', and afterwards you call
"tcsh <script>", SHELL will still be '/bin/bash'. BUT from inside your
script, $0 also doesn't give you the answer you're looking for, as that
will be the name of the script itself unless you called it with "source
<script>".
> My main point is that trying to nail down the shell that you are
> executing under is tricky. Relying on SHELL is probably not a good
> thing. I don't, however, have a definitive answer.
> [...]
> 'bash' and 'tcsh' often masquerade as 'sh' and 'csh', respectively, so
> this [echo $0] check isn't definitive either.
Of course, and as I just said, it doesn't work at all from inside a
script. The only reasonable way to make sure what shell you are
executing under _as a script_ is to explicitly state which one you want
it to be by putting the "#!"-line in front of it.
Whether you get "the real sh" or just a symlink to bash doesn't matter
in this case, because bash behaves just as sh would when called with
this name. I don't know about tcsh, but i'd expect the same.
Stefan
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