[BASH] Script to manage background scripts (running, finished, exit code) Post: 302921390

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Top Forums Shell Programming and Scripting [BASH] Script to manage background scripts (running, finished, exit code) Post 302921390 by Corona688 on Thursday 16th of October 2014 04:45:05 PM

10-16-2014

Registered User

I don't think "unset" really does what you think it does -- deleting from the middle of an array like that. Whenever I do that I end up with "holes", indexes that still exist but have no value. Associative arrays in shell is pretty chancy anyhow, you often won't have a bash new enough, or have bash at all.

Why keep an array of arguments when you already have one, $@

A construct I often use:

Code:

#!/bin/bash

# This is a ring buffer.  Append at PIDS[$PW], read at PIDS[$PR].
# PW increments when a process is added, PR when a process dies,
# and both wrap at MAX.  Order is not important when removing
# since it shuffles the last process to whatever got deleted.
PIDS=()
PW=0
PR=0
MAX=2

running() {     # running "arrayindex"
        ps "${PIDS[$1]}" >/dev/null
}

add() {         # add "pid"
        PIDS[$PW]="$1"
        PW=$(( (PW+1)%MAX ))
        ((TOTAL++))
}

rem() {         # rem "arrayindex"
        # Take PID from the end, plunk it where the one to be deleted is
        PW=$(( (PW-1) % MAX ))
        [[ "$PW" -lt 0 ]] && PW=$((PW+MAX))

        PIDS[$PR]="${PIDS[$PW]}"
        ((TOTAL--))
}

# Start each given program in turn
for X in "$@"
do
        while [[ "$TOTAL" -ge "$MAX" ]]
        do
        for((N=0, I=PR; (TOTAL>=MAX) && (N<TOTAL); N++, I=(I+1)%MAX ))
        do
                if ! running "$I"
                then
                        rem "$I"
                        break
                fi
        done
                [[ "$TOTAL" -ge "$MAX" ]] && sleep 0.1
        done

        # Refers to array indexes, i.e. /tmp/$$-0 for array index 0.
        $X >/tmp/$$-$PW &
        add "$!"
done

while [[ "$TOTAL" -ge "$MAX" ]]
do
        for((N=0, I=PR; N<$TOTAL; N++, I=(I+1)%MAX ))
        do
                if ! running "$I"
                then
                        rem "$I"
                        break
                fi
        done
done

wait
rm -f /tmp/$$-*

Last edited by Corona688; 10-16-2014 at 05:54 PM..

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LEARN ABOUT REDHAT

pidof

PIDOF(8)						Linux System Administrator's Manual						  PIDOF(8)

NAME

       pidof -- find the process ID of a running program.

SYNOPSIS

       pidof [-s] [-x] [-o omitpid] [-o omitpid..]  program [program..]

DESCRIPTION

       Pidof  finds  the  process  id's (pids) of the named programs. It prints those id's on the standard output. This program is on some systems
       used in run-level change scripts, especially when the system has a System-V like rc structure. In that case these scripts  are  located	in
       /etc/rc?.d, where ? is the runlevel. If the system has a start-stop-daemon (8) program that should be used instead.

OPTIONS

       -s     Single shot - this instructs the program to only return one pid.

       -x     Scripts too - this causes the program to also return process id's of shells running the named scripts.

       -o     Tells  pidof  to omit processes with that process id. The special pid %PPID can be used to name the parent process of the pidof pro-
	      gram, in other words the calling shell or shell script.

NOTES

       pidof is simply a (symbolic) link to the killall5 program, which should also be located in /sbin.

       When pidof is invoked with a full pathname to the program it should find the pid of, it is reasonably safe. Otherwise it is  possible  that
       it returns pids of running programs that happen to have the same name as the program you're after but are actually other programs.

SEE ALSO

       shutdown(8), init(8), halt(8), reboot(8)

AUTHOR

       Miquel van Smoorenburg, miquels@cistron.nl

								    01 Sep 1998 							  PIDOF(8)