exit(3) - Linux manual page (original) (raw)

exit(3) Library Functions Manual exit(3)

NAME top

   exit - cause normal process termination

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <stdlib.h>**

   **[[noreturn]] void exit(int** _status_**);**

DESCRIPTION top

   The **exit**() function causes normal process termination and the
   least significant byte of _status_ (i.e., _status & 0xFF_) is returned
   to the parent (see [wait(2)](../man2/wait.2.html)).

   All functions registered with [atexit(3)](../man3/atexit.3.html) and [on_exit(3)](../man3/on%5Fexit.3.html) are called,
   in the reverse order of their registration.  (It is possible for
   one of these functions to use [atexit(3)](../man3/atexit.3.html) or [on_exit(3)](../man3/on%5Fexit.3.html) to register
   an additional function to be executed during exit processing; the
   new registration is added to the front of the list of functions
   that remain to be called.)  If one of these functions does not
   return (e.g., it calls [_exit(2)](../man2/%5Fexit.2.html), or kills itself with a signal),
   then none of the remaining functions is called, and further exit
   processing (in particular, flushing of [stdio(3)](../man3/stdio.3.html) streams) is
   abandoned.  If a function has been registered multiple times using
   [atexit(3)](../man3/atexit.3.html) or [on_exit(3)](../man3/on%5Fexit.3.html), then it is called as many times as it was
   registered.

   All open [stdio(3)](../man3/stdio.3.html) streams are flushed and closed.  Files created
   by [tmpfile(3)](../man3/tmpfile.3.html) are removed.

   The C standard specifies two constants, **EXIT_SUCCESS** and
   **EXIT_FAILURE**, that may be passed to **exit**() to indicate successful
   or unsuccessful termination, respectively.

RETURN VALUE top

   The **exit**() function does not return.

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────┬───────────────┬─────────────────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────┼───────────────┼─────────────────────┤
   │ **exit**()                   │ Thread safety │ MT-Unsafe race:exit │
   └──────────────────────────┴───────────────┴─────────────────────┘

   The **exit**() function uses a global variable that is not protected,
   so it is not thread-safe.

STANDARDS top

   C11, POSIX.1-2008.

HISTORY top

   C89, POSIX.1-2001, SVr4, 4.3BSD.

NOTES top

   The behavior is undefined if one of the functions registered using
   [atexit(3)](../man3/atexit.3.html) and [on_exit(3)](../man3/on%5Fexit.3.html) calls either **exit**() or [longjmp(3)](../man3/longjmp.3.html).  Note
   that a call to [execve(2)](../man2/execve.2.html) removes registrations created using
   [atexit(3)](../man3/atexit.3.html) and [on_exit(3)](../man3/on%5Fexit.3.html).

   The use of **EXIT_SUCCESS** and **EXIT_FAILURE** is slightly more portable
   (to non-UNIX environments) than the use of 0 and some nonzero
   value like 1 or -1.  In particular, VMS uses a different
   convention.

   BSD has attempted to standardize exit codes (which some C
   libraries such as the GNU C library have also adopted); see the
   file _<sysexits.h>_.

   After **exit**(), the exit status must be transmitted to the parent
   process.  There are three cases:

   •  If the parent has set **SA_NOCLDWAIT**, or has set the **SIGCHLD**
      handler to **SIG_IGN**, the status is discarded and the child dies
      immediately.

   •  If the parent was waiting on the child, it is notified of the
      exit status and the child dies immediately.

   •  Otherwise, the child becomes a "zombie" process: most of the
      process resources are recycled, but a slot containing minimal
      information about the child process (termination status,
      resource usage statistics) is retained in process table.  This
      allows the parent to subsequently use [waitpid(2)](../man2/waitpid.2.html) (or similar)
      to learn the termination status of the child; at that point the
      zombie process slot is released.

   If the implementation supports the **SIGCHLD** signal, this signal is
   sent to the parent.  If the parent has set **SA_NOCLDWAIT**, it is
   undefined whether a **SIGCHLD** signal is sent.

Signals sent to other processes If the exiting process is a session leader and its controlling terminal is the controlling terminal of the session, then each process in the foreground process group of this controlling terminal is sent a SIGHUP signal, and the terminal is disassociated from this session, allowing it to be acquired by a new controlling process.

   If the exit of the process causes a process group to become
   orphaned, and if any member of the newly orphaned process group is
   stopped, then a **SIGHUP** signal followed by a **SIGCONT** signal will be
   sent to each process in this process group.  See [setpgid(2)](../man2/setpgid.2.html) for an
   explanation of orphaned process groups.

   Except in the above cases, where the signalled processes may be
   children of the terminating process, termination of a process does
   _not_ in general cause a signal to be sent to children of that
   process.  However, a process can use the [prctl(2)](../man2/prctl.2.html) **PR_SET_PDEATHSIG**
   operation to arrange that it receives a signal if its parent
   terminates.

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   man-pages@man7.org

Linux man-pages 6.10 2024-07-23 exit(3)

Pages that refer to this page:man(1), _exit(2), kill(2), vfork(2), wait(2), abort(3), assert(3), assert_perror(3), atexit(3), err(3), error(3), EXIT_SUCCESS(3const), on_exit(3), pthread_create(3), pthread_detach(3), pthread_exit(3), sd_bus_set_exit_on_disconnect(3), setjmp(3), stdin(3), stdio(3), sysexits.h(3head), tmpfile(3)