bin/34811: sh(1) "jobs" is not pipeable

Jilles Tjoelker jilles at
Fri Apr 3 12:40:06 PDT 2009

The following reply was made to PR bin/34811; it has been noted by GNATS.

From: Jilles Tjoelker <jilles at>
To: bug-followup at, slaven.rezic at,
	Martin.Kaeske at, kerochan2 at
Subject: Re: bin/34811: sh(1) "jobs" is not pipeable
Date: Fri, 3 Apr 2009 21:34:18 +0200

 The way I read POSIX, I think this does not have to work. Commands in a
 pipeline with two or more commands may or may not be executed in a
 subshell (this 'or' applies to each of the commands individually), and a
 subshell has its own list of unwaited jobs.
 Accordingly,  (jobs)  gives empty output (in /bin/sh as well as bash4).
 bash4 seems to do special trickery with the jobs command in pipelines
 (as permitted): even in commands like  jobs >`tty` | jobs  both give
 proper output. This, however, breaks down if you make it more
 complicated such as by replacing  jobs  with  { jobs; }.
 On the other hand, $(jobs) works in both /bin/sh and bash4, although
 POSIX says that command substitution happens in a subshell. However,
 POSIX also mentions $(jobs -p) in an informative section, and it seems
 If you want to add this feature, evalpipe() in eval.c would probably be
 the place. It would be quite specific to very few builtin commands which
 tend not to be used much in scripts. (Note that slow operations in the
 main shell process cannot be ^Z'ed, and that builtin commands may be
 overridden with functions.)
 Jilles Tjoelker

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