* Inconsistent behaviour between 'jobs' and 'echo "$(jobs)"'
@ 2015-01-19 18:01 Damian Wrobel
[not found] ` <20150120084438.GA751@ein.free.fr>
0 siblings, 1 reply; 4+ messages in thread
From: Damian Wrobel @ 2015-01-19 18:01 UTC (permalink / raw)
To: dash
Hi,
I'm observing an inconsistent behaviour between:
jobs
and
echo "$(jobs)"
Here is the short example:
$ rpm -qv dash
dash-0.5.8-1.fc21.i686
$ /bin/dash
$ sleep 1000 &
$ jobs
[1] + Running sleep 1000
$ echo "$(jobs)"
$ echo `jobs`
$ jobs 2>/dev/null
[1] + Running sleep 1000
$
--
Have a nice day,
Damian
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Inconsistent behaviour between 'jobs' and 'echo "$(jobs)"'
[not found] ` <20150120084438.GA751@ein.free.fr>
@ 2015-01-20 17:01 ` Damian Wrobel
2015-01-20 19:07 ` Seb
2015-01-21 13:42 ` Seb
0 siblings, 2 replies; 4+ messages in thread
From: Damian Wrobel @ 2015-01-20 17:01 UTC (permalink / raw)
To: dash; +Cc: Seb
On 01/20/2015 09:44 AM, Seb wrote:
> On Mon, Jan 19, 2015 at 07:01:53PM +0100, Damian Wrobel wrote:
>
> Hello,
>
>> I'm observing an inconsistent behaviour between:
>> jobs
>> and
>> echo "$(jobs)"
>
> It's because the command is ran in a sub-shell, where there is indeed no
> running job.
>
> Bash has a special mechanism to handle this and get the current shell
> context returned, that's why you may feel some inconsistency here (like
> I myself did :)
There is an application usage [1] where this case is specifically mentioned with
a suggestion that: "For this reason, jobs is generally implemented as a shell
regular built-in."
I basically planned to use the following construction to kill all running jobs:
$ kill $(jobs -p)
Now it looks that even the following doesn't work in a dash:
$ jobs -p | xargs kill
I would prefer not to code something like the following:
$ jobs -p >/tmp/jobs-$$ && kill $(cat /tmp/jobs-$$); rm /tmp/jobs-$$
Have a nice day,
Damian
[1] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/jobs.html
>
> ++
> Seb.
>
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Inconsistent behaviour between 'jobs' and 'echo "$(jobs)"'
2015-01-20 17:01 ` Damian Wrobel
@ 2015-01-20 19:07 ` Seb
2015-01-21 13:42 ` Seb
1 sibling, 0 replies; 4+ messages in thread
From: Seb @ 2015-01-20 19:07 UTC (permalink / raw)
To: dash; +Cc: Damian Wrobel
On Tue, Jan 20, 2015 at 06:01:10PM +0100, Damian Wrobel wrote:
> On 01/20/2015 09:44 AM, Seb wrote:
> >On Mon, Jan 19, 2015 at 07:01:53PM +0100, Damian Wrobel wrote:
> >
> >Hello,
> >
> >>I'm observing an inconsistent behaviour between:
> >> jobs
> >>and
> >> echo "$(jobs)"
> >
> >It's because the command is ran in a sub-shell, where there is indeed no
> >running job.
> >
> >Bash has a special mechanism to handle this and get the current shell
> >context returned, that's why you may feel some inconsistency here (like
> >I myself did :)
>
> There is an application usage [1] where this case is specifically mentioned
> with a suggestion that: "For this reason, jobs is generally implemented as a
> shell regular built-in."
Indeed, it seems the standard requires, or at least expects this to
work:
"The -p option is the only portable way to find out the
process group of a job because different implementations
have different strategies for defining the process group of
the job. Usage such as $(jobs -p) provides a way of
referring to the process group of the job in an
implementation-independent way."
> Now it looks that even the following doesn't work in a dash:
>
> $ jobs -p | xargs kill
For the same reason as above: each member of the pipe is ran in its own
sub-shell.
> I would prefer not to code something like the following:
>
> $ jobs -p >/tmp/jobs-$$ && kill $(cat /tmp/jobs-$$); rm /tmp/jobs-$$
I agree it's not very nice.
++
Seb.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Inconsistent behaviour between 'jobs' and 'echo "$(jobs)"'
2015-01-20 17:01 ` Damian Wrobel
2015-01-20 19:07 ` Seb
@ 2015-01-21 13:42 ` Seb
1 sibling, 0 replies; 4+ messages in thread
From: Seb @ 2015-01-21 13:42 UTC (permalink / raw)
To: dash; +Cc: Damian Wrobel
On Tue, Jan 20, 2015 at 06:01:10PM +0100, Damian Wrobel wrote:
> I would prefer not to code something like the following:
>
> $ jobs -p >/tmp/jobs-$$ && kill $(cat /tmp/jobs-$$); rm /tmp/jobs-$$
As a better alternative, you could maybe try this:
trap : TERM # in case we have something to do after...
/bin/kill -s TERM -$$
Just an idea...
++
Seb.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2015-01-21 13:42 UTC | newest]
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2015-01-19 18:01 Inconsistent behaviour between 'jobs' and 'echo "$(jobs)"' Damian Wrobel
[not found] ` <20150120084438.GA751@ein.free.fr>
2015-01-20 17:01 ` Damian Wrobel
2015-01-20 19:07 ` Seb
2015-01-21 13:42 ` Seb
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