Synchronizing four shell scripts to run one after another in unix

Question

I have 4 shell script to generate a file(let\'s say param.txt) which is used by another tool(informatica) and as the tool is done with processing, it deletes param.txt.

Answer 1

You are experiencing a classical race condition. To solve this issue, you need a shared "lock" (or similar) between your 4 scripts.

There are several ways to implement this. One way to do this in bash is by using the flock command, and an agreed-upon filename to use as a lock. The flock man page has some usage examples which resemble this:

(
    flock -x 200  # try to acquire an exclusive lock on the file
    # do whatever check you want. You are guaranteed to be the only one
    # holding the lock
    if [ -f "$paramfile" ]; then
        # do something
    fi
) 200>/tmp/lock-life-for-all-scripts
# The lock is automatically released when the above block is exited

You can also ask flock to fail right away if the lock can't be acquired, or to fail after a timeout (e.g. to print "still trying to acquire the lock" and restart).

Depending on your use case, you could also put the lock on the 'informatica' binary (be sure to use 200< in that case, to open the file for reading instead of (over)writing)