in reply to
Generate a unique ID
If your program will only run on one system you might also consider a counter stored in a file. Each time the program starts it will access the file, increase the counter and close it again. For handling concurrent runs of your program, you would just sleep(1) if/while your counter-file is locked for writing.
If your programs are running on several systems you might use the IP/MAC-address in conjunction with the counter and have a counter-file on each system....