Re: suppressing shell error output

[Martin Sebor]

Mike Frysinger wrote:
[...]
> which is pretty well ported ... OS X (Darwin), BSD, Linux have it by 
> default ...

True. I looked for a machine w/o it and couldn't find one. I do
recall that we had one where it wasn't available (AIX 4.2 maybe?)
In any case, it's not in POSIX.
(Looking some more... Ah, found one: z/OS UNIX System Services.)

> afaik, which should only error under really bad circumstances, so something 
> like this should work:
> which_binary=`which which 2>/dev/null`
> test -z "$which_binary" && echo no which available
>
> i guess if you're going to be really super anal about it, you'd wrap the whole 
> thing in a local function:
> function my_which() {
>     if test -z "$which_binary" ; then
>         ... your workaround here ...

My point was that if I go to the trouble of implementing a workaround
for a missing which I might as well use it instead and save myself the
effort of maintaining two solutions.

>     else
>         $which_binary "$@"
>     fi
> }
>
> note that you cant rely on exit status on which, just output ... stupid OS X 
> ships a broken which that always exits 0 even if the specified utility isnt 
> found

POSIX should really add which as a requirement. It's essential,
non-trivial to work around when it doesn't exist, and widely
implemented.

Martin