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How to run scripts parallely inside shell script?

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# 8  
Old 10-14-2014
I didn't have any issues with this approach using bash and ksh:

Code:
./script1 & p1=$!
./script2 & p2=$!
./script3 & p3=$!

wait $p1 ; rc1=$?
wait $p2 ; rc2=$?
wait $p3 ; rc3=$?

# Some debug output
printf "Job 1 (%d): %d\n" $p1 $rc1
printf "Job 2 (%d): %d\n" $p2 $rc2
printf "Job 3 (%d): %d\n" $p3 $rc3

if [ $rc1 = 0 ] && [ $rc2 = 0 ] && [ $rc1 = 0 ]
then
    ./script4
fi

# 9  
Old 10-14-2014
Quote:
Originally Posted by Chubler_XL
I didn't have any issues with this approach using bash and ksh:

Code:
./script1 & p1=$!
./script2 & p2=$!
./script3 & p3=$!

wait $p1 ; rc1=$?
wait $p2 ; rc2=$?
wait $p3 ; rc3=$?

# Some debug output
printf "Job 1 (%d): %d\n" $p1 $rc1
printf "Job 2 (%d): %d\n" $p2 $rc2
printf "Job 3 (%d): %d\n" $p3 $rc3

if [ $rc1 = 0 ] && [ $rc2 = 0 ] && [ $rc1 = 0 ]
then
    ./script4
fi

Easier with bitwise-or:

Code:
./script1 & p1=$!
./script2 & p2=$!
./script3 & p3=$!

# once rc goes non-zero, it stays that way
wait $p1 ; rc=$?
wait $p2 ; rc=$(( $rc | $? ))
wait $p3 ; rc=$(( $rc | $? ))


if [ $rc = 0 ]
then
    ./script4
fi

It's not a big deal for 3 scripts. But if you spawned 30 or so...

You do lose the ability to tell which script failed though.
# 10  
Old 10-15-2014
Quote:
Originally Posted by achenle
Easier with bitwise-or:

Code:
./script1 & p1=$!
./script2 & p2=$!
./script3 & p3=$!

# once rc goes non-zero, it stays that way
wait $p1 ; rc=$?
wait $p2 ; rc=$(( $rc | $? ))
wait $p3 ; rc=$(( $rc | $? ))


if [ $rc = 0 ]
then
    ./script4
fi

It's not a big deal for 3 scripts. But if you spawned 30 or so...

You do lose the ability to tell which script failed though.
If you don't care which ones fail, there is no need to keep track of the individual return codes at all:
Code:
./script1 & p1=$!
./script2 & p2=$!
./script3 & p3=$!

# Execute script4 only if all other scripts complete successfully:
wait $p1 && wait $p2 && wait $p3 && ./script4
rc=$?

# Wait for remaining children if script1 or script2 failed:
wait
exit $rc

Note that the shell is only required to keep track of CHILD_MAX processes and the standards say CHILD_MAX can be as small as 25. So, if you want to keep track of more than 25 background processes, verify that your shell can keep track of all of them by checking the CHILD_MAX limit on your system with the command:
Code:
getconf CHILD_MAX

Also note that if you have CHILD_MAX processes running, attempts to start any more processes (foreground or background) will fail.
# 11  
Old 10-15-2014
@ Scrunitizer: Seriously?
Thats nice and so small.

Guess i like writing 'gui's way too much...
That makes those scripts always so immense :P
How to run scripts parallely inside shell script?-demoscriptjpg
Last edited by sea; 10-15-2014 at 06:55 PM..
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