How to set process ID in Linux for a specific program

Question

I was wondering if there is some way to force to use some specific process ID to Linux to some application before running it. I need to know in advance the process ID.

Answer 1

You could just repeatedly call fork() to create new child processes until you get a child with the desired PID. Remember to call wait() often, or you will hit the per-user process limit quickly.

This method assumes that the OS assigns new PIDs sequentially, which appears to be the case eg. on Linux 3.3.

The advantage over the ns_last_pid method is that it doesn't require root permissions.