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Full Discussion: background processing in BASH
Operating Systems Linux background processing in BASH Post 302311224 by otheus on Tuesday 28th of April 2009 08:29:32 AM
Old 04-28-2009
Quote:
In the present scenario although Child2 failed first ( exit 1 ) the status is not displayed until Child1 is complete.
That's because you are waiting for the first child before anything else. You can try plain "wait", but that doesn't return until ALL children have completed.

What you can do is set up a wait-loop, and then set up a signal handler to call "jobs" or check on the specific status of any jobs; and set up an alarm-like thingy to wake up the signal handler. The wait call then gets pre-empted. So for instance, something like this (untested) in bash might work:

Code:
job1 & 
job2 &

# turn off immeidate job notification
set +b

# trap USR1 signal with null action
trap test USR1

# set up an alarm
{ sleep 1; kill -USR1 $$; } &
# disown so it does not show up in job table
# (with other shells, this can be emulated by starting it as its own session leader)
disown $!   # acts differently in ksh

# keep waiting till all jobs are complete
while ! wait; do 
   DONE=`jobs -n | sed -n '/ Done / s/^\[\([0-9]*\)\].*/\1/p'`
   if [ -n "$DONE" ]; then 
      echo -n "Jobs $DONE were completed at " 
      date
   fi
   # restart timer
   { sleep 1; kill -USR1 $$ ; } &
   disown $!
done

When wait exits with 0, there are no remaining background tasks, and the loop terminates. If you don't have bash, but have "setsid", you can effectively disown a process that way.
 

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LEARN ABOUT HPUX

queuedefs

queuedefs(4)						     Kernel Interfaces Manual						      queuedefs(4)

NAME

       queuedefs - queue description file for at, batch, and crontab

SYNOPSIS

DESCRIPTION

       The  file  describes  the characteristics of the queues managed by (see cron(1M)).  Each non-comment line in this file describes one queue.
       The format of the lines are as follows:

	      [njob[nice[nwait

       The fields in this line are:

	      q 	The name of the queue, such that is the default queue for jobs started by (see at(1)), is the queue for  jobs  started	by
			(see  at(1)),  and  is	the  queue  for jobs run from a file (see crontab(1)).	Queue names through designate user-defined
			queues.

	      njob	The maximum number of jobs that can be run simultaneously in that queue.  Although any number can be specified here,  (see
			cron(1M))  by  default limits the number of jobs that can be run on all the queues to 100.  This limitation can be removed
			by setting the variable to 1 in the file.

	      nice	The value to give to all jobs in that queue that are not run with a user ID of	super-user  (see  nice(1)).   The  default
			value is 2.

	      nwait	The number of seconds to wait before rescheduling a job that was deferred because more than njob jobs were running in that
			job's queue, or because more than 100 jobs were running in all the queues (see njob above).

EXAMPLES

       Consider the following file:

       The file is interpreted as follows:

	      The	     queue, for jobs (see at(1)), can have up to 4 jobs running simultaneously, and those jobs will be run with a value of
			     1.

			     Since  no	nwait value is given, if a job cannot be run because too many other jobs are running, will wait 60 seconds
			     before trying again to run it (see cron(1M)).

	      The	     queue, for jobs (see at(1)), can have up to 2 jobs running simultaneously.  Those jobs will be run with a value of 2.
			     If a job cannot be run because too many other jobs are running, will wait 90 seconds before trying again to run it.

       All  other  queues  can have up to 100 jobs running simultaneously.  They will be run with a value of 2, and if a job cannot be run because
       too many other jobs are running, will wait 60 seconds before trying again to run it.

SEE ALSO

       at(1), nice(1), crontab(1), cron(1M), proto(4).

STANDARDS CONFORMANCE

																      queuedefs(4)
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