|FORK(2)||System Calls Manual||FORK(2)|
fork — create a
fork() causes creation of a new process.
The new process (child process) is an exact copy of the calling process
(parent process) except for the following:
In general, the child process should call _exit(2) rather than exit(3). Otherwise, any stdio buffers that exist both in the parent and child will be flushed twice. Similarly, _exit(2) should be used to prevent atexit(3) routines from being called twice (once in the parent and once in the child).
In case of a threaded program, only the thread calling
fork() is still running in the child processes.
Child processes of a threaded program have additional restrictions, a child must only call functions that are async-signal-safe. Very few functions are asynchronously safe and applications should make sure they call exec(3) as soon as possible.
Upon successful completion,
a value of 0 to the child process and returns the process ID of the child
process to the parent process. Otherwise, a value of -1 is returned to the
parent process, no child process is created, and the global variable
errno is set to indicate the error.
fork() will fail and no child process will
be created if:
RLIMIT_NPROCon the total number of processes under execution by this user id would be exceeded.
fork() function conforms to
IEEE Std 1003.1-1990 (“POSIX.1”).
fork() system call appeared in
Version 6 AT&T UNIX.
|June 10, 2004||NetBSD-7.0.1|