> Am 29.04.2016 um 14:15 schrieb Greg Wooledge <[email protected]>:
>
> On Thu, Apr 28, 2016 at 10:38:53AM -0600, Eric Blake wrote:
>> Bash has code to special-case 'jobs |' when it can obviously tell that
>> you are running the jobs builtin as the sole command of the left side of
>> a pipe, to instead report about the jobs of the parent shell,
>
> Oh, that's interesting. I didn't know that.
Me too.
I understand that the behavior of the builtin `jobs` changes, in case it
discovers that it's run a subshell. But what is happening here:
$ sleep 300 &
[1] 31766
$ function lister() { date; jobs; }
$ lister
Fri Apr 29 15:29:46 CEST 2016
[1]+ Running sleep 300 &
$ lister | cat
Fri Apr 29 15:30:00 CEST 2016
[1] Done date
My question is: why does the `date` command show up as "done" at all? I would
expect the output to be just empty.
> but that
>> special-case code cannot kick in if you hide the execution of jobs,
>> whether by hiding it inside a function as you did, or by other means
>> such as:
>> $ eval jobs | grep vim
>
> In general, if you want to filter the output of "jobs" or some other
> builtin that changes its behavior when invoked in a subshell, then
> you need to avoid the subshell. That means no pipeline, no command
> substitution, etc. Basically that leaves you with a temporary file.
>
> tmpfile=... # boilerplate code to create a temp file on whatever OS
> trap 'rm -f "$tmpfile"' EXIT
> jobs > "$tmpfile"
> if grep -q vim "$tmpfile"; then ...
Depending on the overall program, this might work to avoid a subshell:
if grep -q vim < <(realjobs); then ...
-- Reuti
