If I have a process, and I clone it, is the PID the same?

Question

Just a quick question, if I clone a process, the PID of the cloned process is the same, yes ? fork() creates a child process where the PID differs, but everything else is th

Answer 1

Threads (which have the same visible 'pid') are implemented with the clone() call. When the flag CLONE_THREAD is supplied then the new process (a 'thread') share the Thread Group Identifier (TGID) with its creator process. getpid actually returns the TGID.

See the clone manpage for more details.

In summary the real PID, as seen by the kernel is always different. The visible PID is the same for threads.