Shell Programming and Scripting

I have script 3 scripts 1 parent (p1) and 2 children child1 and child2

I have script 3 scripts
1 parent
2 children
child1
child2

In the code below the 2 child processes fire almost Instantaneously in
the background, Is that possible to know the status of pass/fail of each
process "as it happens" ?

In the present scenario although Child2 failed first ( exit 1 ) the status is not displayed until Child1 is complete.

I would really apprecitate your help.


Mother Process:
--------------------------------------

#!/bin/bash

echo -e " Parent continued process 1"
echo -e " Parent continued process 2"
echo -e " ** Kicking off a child process C1** "
./child1 &
t1=$!
echo -e " Parent continued process 3"
echo -e " Parent continued process 4"
echo -e " ** Kicking off a child process C2** "
./child2 &
t2=$!

wait $t1
if [ $? -ne 0 ]
then
echo " Child Process C1 failed !!! "
fi

wait $t2
if [ $? -ne 0 ]
then
echo " Child Process C2 failed !!! "
fi

exit 0

-------------------------------------

Child1
------
#!/bin/bash
echo -e " in child process 1 "
sleep 2
echo -e " in child process 2 "
sleep 2
echo -e " in child process 3 "
sleep 7
exit 0 # success


Child2
------
#!/bin/bash
echo -e " in child process 4"
echo -e " in child process 5"
echo -e " in child process 6"
exit 1 # failed


Thanks,
SSR.

Why not create a file, pipe the child process output to the file, and read the results FROM the file after the child exits? The basic technique is ancient, easy, and portable over many operating systems.

is there a way besides that ?

This is bash we are talking about, there are ALWAYS other ways!

One might be to write a pipe for each child process, let the child feed its pipe, and let the parent read them. This is WAY overkill for your example, and there are opportunities for failure, but I have used it successfully. Google for examples.

You might consider defining the child processes as functions instead of scripts, then you do not have the extra I/O.

this is just a prototype here, but in real world these are different scripts which are running. How feasible is it to be defined as a function ?

That depends upon what the final scripts will hold and use, how much data end/or environment they need to have in common with the parent, etc. If they are short and simple extensions of what you already have then they make good functions. If they are extensive or do many things, you may be better off leaving them scripts.

Is there some reason that you do not want to use files? I have used the technique for recursive scripts that ran dozens of copies for very short periods of time to gather lots of information very quickly: it works!

The only problem I see with using files is I have to add lines to the child scripts to write a status to a log which my main process keeps reading.