_EXIT(2) System Calls Manual _EXIT(2)

_exit, _Exit — terminate the calling process

#include <unistd.h>

void
_exit(int status);

#include <stdlib.h>

void
_Exit(int status);

The () and () functions terminate a process with the following consequences:

  • All threads in the process are terminated.
  • All open file descriptors in the calling process are closed. This may entail delays; for example, waiting for output to drain. A process in this state may not be killed, as it is already dying.
  • If the parent process of the calling process has an outstanding wait(2) call or catches the SIGCHLD signal, it is notified of the calling process's termination and status is set as defined by wait(2). (Note that typically only the lower 8 bits of status are passed on to the parent, thus negative values have less meaning.)
  • The parent process ID of all of the calling process's existing child processes are set to 1; the initialization process (see the DEFINITIONS section of intro(2)) inherits each of these processes.
  • If the termination of the process causes any process group to become orphaned (usually because the parents of all members of the group have now exited; see Orphaned Process Group in intro(2)), and if any member of the orphaned group is stopped, the SIGHUP and SIGCONT signals are sent to all members of the newly orphaned process group.
  • If the process is a controlling process (see intro(2)), the SIGHUP signal is sent to the foreground process group of the controlling terminal, and all current access to the controlling terminal is revoked.

Most C programs call the library routine exit(3), which flushes buffers, closes streams, unlinks temporary files, etc., and then calls ().

_exit() and _Exit() can never return.

fork(2), intro(2), sigaction(2), wait(2), exit(3), sysexits(3)

The _exit() function conforms to IEEE Std 1003.1-2008 (“POSIX.1”). The _Exit() function conforms to ISO/IEC 9899:1999 (“ISO C99”).

An exit() system call first appeared in Version 1 AT&T UNIX. It accepts the status argument since Version 2 AT&T UNIX. An _exit() variant first appeared in Version 7 AT&T UNIX. The _Exit() function appeared in OpenBSD 3.6.

February 18, 2022 OpenBSD 7.5