Here is the script:
#!/bin/bash
# multiple-processes.sh: Run multiple processes on an SMP box.
# Script written by Vernia Damiano.
# Used with permission.
# Must call script with at least one integer parameter
#+ (number of concurrent processes).
# All other parameters are passed through to the processes started.
INDICE=8 # Total number of process to start
TEMPO=5 # Maximum sleep time per process
E_BADARGS=65 # No arg(s) passed to script.
if [ $# -eq 0 ] # Check for at least one argument passed to script.
then
echo "Usage: `basename $0` number_of_processes [passed params]"
exit $E_BADARGS
fi
NUMPROC=$1 # Number of concurrent process
shift
PARAMETRI=( "$@" ) # Parameters of each process
function avvia() {
local temp
local index
temp=$RANDOM
index=$1
shift
let "temp %= $TEMPO"
let "temp += 1"
echo "Starting $index Time:$temp" "$@"
sleep ${temp}
echo "Ending $index"
kill -s SIGRTMIN $$
}
function parti() {
if [ $INDICE -gt 0 ] ; then
avvia $INDICE "[EMAIL PROTECTED]" &
let "INDICE--"
else
trap : SIGRTMIN
fi
}
trap parti SIGRTMIN
while [ "$NUMPROC" -gt 0 ]; do
parti;
let "NUMPROC--"
done
wait
trap - SIGRTMIN
exit $?
: <<SCRIPT_AUTHOR_COMMENTS
I had the need to run a program, with specified options, on a number of
different files, using a SMP machine. So I thought [I'd] keep running
a specified number of processes and start a new one each time . . . one
of these terminates.
The "wait" instruction does not help, since it waits for a given process
or *all* process started in background. So I wrote [this] bash script
that can do the job, using the "trap" instruction.
--Vernia Damiano
SCRIPT_AUTHOR_COMMENTS
On 6/26/05, Sammo <[EMAIL PROTECTED]> wrote:
> 2.05b.0(1)-release
>
> I seem to be having problems with one of the examples in the Advanced
> Bash Scripting Guide [1]. The script is supposed to start a specified
> number of processes, and when each process finishes, it sends a trap
> signal, which starts a new process. I think the script is correct, but
> it's not working as expected.
>
> This is what is happening: The first process that finishes sends a
> trap signal to $$, and a new process is started (as expected). But
> when subsequent processes try to send the trap signal, they can't find
> the process. Also, seems that the "wait" command is only waiting until
> the first process finishes, instead of waiting for all of them to
> finish.
>
> Well, here is the output:
>
> $ ./multiple-processes.sh 3
> Starting 8 Time:3
> Starting 7 Time:1
> Starting 6 Time:4
> Ending 7
> Starting 5 Time:4
>
> $ Ending 8
> ./multiple-processes.sh: line 37: kill: (3944) - No such process
> Ending 6
> ./multiple-processes.sh: line 37: kill: (3944) - No such process
> Ending 5
> ./multiple-processes.sh: line 37: kill: (3944) - No such process
>
> Please, can somebody help?!
>
> References:
>
> [1] Example 29-8. Running multiple processes (on an SMP box),
> http://www.tldp.org/LDP/abs/html/debugging.html#MULTIPLEPROC
>
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