Debian Programming :: Script To Execute String From Text File

I am having trouble writing a script that monitors a text file. When the file contains number 1 (or any other string that is not a command) it does nothing, but when it is something different from 1, it executes that command.

So, there are 2 files: monitor.mon - this is the file that will be checked constanlty; and test.sh - the script that does the job. The monitor.mon file will have its content modified by php. This means a web page will have a form where I input commands and writes does commands in the file. Test.sh will watch when the file's content changes from character 1 to a command, execute that command and write back a 1 so it will not execute it more times.

I tried combining while and if but with no success. Tried reading the file with cat and grep -e but it doesn't seem to recognize when content changes.