Write a shell script that produces a file of sequential numbers by reading the last number in the file, adding 1 to it, and then appending it to the file. Run one instance of the script in the background and one in the foreground, each accessing the same file.(Hint: run a command ending in a & to run in the background) -- Assume integer numbers.

How long does it take before a race condition manifests itself? What is the critical region? Modify the script to prevent the race.

(Hint: use

ln file file.lock

to lock the data file.)