Shell Programming and Scripting

I've been thinking about a peculiar problem, and so far haven't been able to find out a convincing solution to that.

To put it simply, I have a shell script (assume it to be parent_script.sh), calling another shell script (child_script.sh) 5 times, in nohup mode to be executed in the background. The parent script is something like this

Code:

for i in $(seq 1 5)
do
nohup ./child_script.sh &
done

For each run, child_script generates 10 files in a particular folder. So for a single run, parent_script.sh will be having 50 files generated.

After all the 50 files are created in that folder, I need to rename these files. For instance, if the files are created as abc.txt, def.txt.....xyz.txt, then after renaming, these will be abc_01.txt, def_02.txt....xyz_50.txt.

Now in order to start the renaming process, I've thought of adding a small code block in the parent_script.sh, something like below

Code:

i=1
while [ $i -eq 1 ]
do
proc_count= ps -ef | grep child_script.sh | grep -v grep | wc -l

if [ $proc_count -eq 0 ]
then
<the renaming stuff>
i=0

fi

sleep 10

done

This will ensure that the renaming process will wait until all the 5 parallel threads get completed, then start renaming the files, and then finish the parent script.

My problem is, this file generation process for the 5 threads may take quite a few hours to get completed, may be 2-3 hours on an average. But as per the requirement, the parent script is invoked once every hour. So it may very well happen that at a time more than 5 parallel threads of child_script.sh are running, for multiple executions of the parent script. In such a scenario, the count of running processes of child_script.sh will never be zero.

What can be an alternative way out for this? I'm not much of an advanced unix user, and any help will be much appreciated.

N.B. for each hourly run of the parent script, the renaming sequence of 1 to 50 will recycle, i.e. for first hour, the files will be abc_01.txt...xyz_50.txt, similarty for the files created in the second hour will be named ABC_01.txt...XYZ_50.txt

As achenle points out use the shell built-in wait command which will wait for all child processes started in this shell:

Code:

for i in $(seq 1 5)
do
nohup ./child_script.sh &
done

# wait for child processes to finish
wait

<the renaming stuff>

A lock file, testing for an output file, or incron are all workable.

Mike