Date: Thu, 4 Dec 2008 02:20:03 GMT From: Nate Eldredge <neldredge@math.ucsd.edu> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/102357: tcsh(1)/csh(1) jobs control: sometimes 'fg' command doesn't capture back the background process Message-ID: <200812040220.mB42K3cW081473@freefall.freebsd.org>
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The following reply was made to PR bin/102357; it has been noted by GNATS.
From: Nate Eldredge <neldredge@math.ucsd.edu>
To: bug-followup@FreeBSD.org, todor.dragnev@gmail.com
Cc:
Subject: Re: bin/102357: tcsh(1)/csh(1) jobs control: sometimes 'fg' command
doesn't capture back the background process
Date: Wed, 3 Dec 2008 18:19:01 -0800 (PST)
It looks like this is a "feature".
csh has a notion of the "current" job. If you run 'jobs', the current job
will be marked with a +. Running fg, bg, etc without arguments acts on
the current job.
There is code in tcsh's bg command that explicitly sets the job just
backgrounded not to be the current job (calling the pclrcurr() function).
If there are other jobs running, one of them becomes the current job. If
no other jobs are running, as in your test case, then there will be no
current job. (pcurrent is set to NULL.) Note at this point that the
'jobs' command doesn't display a + by your job. 'fg' without arguments
correctly says there is no current job. 'fg %1' will do what you
want, of course.
I am not sure what is the point of this behavior, but it definitely seems
intentional. It goes back at least as far as tcsh 6.00 circa 1995. I
could imagine that some scripts may depend on it now so I think maybe it
should not be changed. However, I've attached a patch that will eliminate
this behavior, if you want to try it. With the patch a backgrounded
current job remains current.
When you run another job ('man' in your example), it becomes the current
job when it is started. When it completes, it can't be the current job
anymore, so, as before, tcsh looks for another job to set as the current
one. The only candidate is 'tail -f', so it becomes the current job
again. At this point if you run 'jobs' again you'll see the + indicator,
and fg/bg will work as you expect.
--- tcsh.orig/sh.proc.c 2007-10-16 09:18:39.000000000 -0700
+++ src/contrib/tcsh/sh.proc.c 2008-12-03 18:01:35.000000000 -0800
@@ -1546,8 +1546,6 @@
np->p_flags &= ~PFOREGND;
}
} while ((np = np->p_friends) != pp);
- if (!foregnd)
- pclrcurr(pp);
(void) pprint(pp, foregnd ? NAME | JOBDIR : NUMBER | NAME | AMPERSAND);
/* GrP run jobcmd hook if foregrounding */
--
Nate Eldredge
neldredge@math.ucsd.edu
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