Manual Pages  — EXIT

1. Call the functions registered with the atexit(3) function, in the reverse order of their registration.
2. Flush all open output streams.
3. Close all open streams.
4. Unlink all files created with the tmpfile(3) function.

The _Exit() function terminates without calling the functions registered with the atexit(3) function, and may or may not perform the other actions listed. Both functions make the low-order eight bits of the status argument available to a parent process which has called a wait(2)-family function.

The C Standard (ISO/IEC 9899:1999 ("ISO C99")) defines the values 0, EXIT_SUCCESS, and EXIT_FAILURE as possible values of status. Cooperating processes may use other values; in a program which might be called by a mail transfer agent, the values described in sysexits(3) may be used to provide more information to the parent process.

Note that exit() does nothing to prevent bottomless recursion should a function registered using atexit(3) itself call exit(). Such functions must call _Exit() instead (although this has other effects as well which may not be desired).