Re: How to detect bash?

[mwoehlke]

Stephane Chazelas wrote:
> On Tue, Oct 10, 2006 at 06:14:22PM -0500, mwoehlke wrote:
> [...]
> > > $ zsh -c 'echo "`/dev/null 2>&1`"' bash
> > > bash: /dev/null: Permission denied
> > >
> > > $ zsh
> > > $ ARGV0=bash ash -c 'echo "`/dev/null 2>&1`"; echo $BASH'
> > > bash: /dev/null: Permission denied
> > Eh? I get:
> >
> > $ zsh -c 'echo "`/dev/null 2>&1`"' bash
> > zsh:1: permission denied: /dev/null
>
> Well, I do get what I said with zsh 4.3.2
>
> > $ ARGV0=bash ash -c 'echo "`/dev/null 2>&1`"; echo $BASH'
> > /dev/null: permission denied
>
> (note that this command must be run from zsh which uses
> ARGV0=... to set ash's argv[0]).
>
> You must have an older /ash/ than I have mine is one of the
> OpenBSD based sh ones (found on debian).

Maybe, I never use ash or zsh (intentionally, anyway; IIRC Cygwin uses 
ash under the covers some time, but I never use either interactively), 
so I just got whatever versions came with the system (FC4). I don't 
doubt that you can make these work, I'm just noting that ability/method 
of circumventing the aforementioned test is inconsistent. :-)

> > So neither of your counter-examples is working for me (although both 
> > look like they *should*; go figure).
>
> Though I'd bet the third one with .zshenv worked.
>
> > But since you didn't counter 
> > BASH_SUBSHELL (and since I'm too lazy to change it now) I guess I'll 
> > stick with that. :-)
>
> BASH_SUBSHELL is a relatively recent addition to bash. Most
> systems still don't have a bash3.
>
> $ bash -c 'echo "$BASH_VERSION, <$BASH_SUBSHELL>"'
> 2.05b.0(2)-release, <>

Ah, well, I have 3.1.17 builds available for 9 of 10 systems these 
scripts may need to run on (plus two others) and the tenth has 3.1.0. 
I'm not particularly concerned if I'm only catching 3.0+ versions, since 
that will also insulate me from anything else that is 3.0+-specific 
(i.e. it's OK if I use new features because I've ensured that I have 
them). Thanks for pointing this out, though.

--
Matthew
Will your shell have salvation? Only if it's Bourne Again.