bionic (3) exit.3.gz

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NAME

       exit - cause normal process termination

SYNOPSIS

       #include <stdlib.h>

       void exit(int status);

DESCRIPTION

       The  exit()  function causes normal process termination and the value of status & 0377 is returned to the
       parent (see wait(2)).

       All functions registered with atexit(3) and  on_exit(3)  are  called,  in  the  reverse  order  of  their
       registration.   (It  is possible for one of these functions to use atexit(3) or on_exit(3) 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), or kills itself with a signal), then none of  the  remaining  functions  is  called,  and
       further  exit  processing  (in particular, flushing of stdio(3) streams) is abandoned.  If a function has
       been registered multiple times using atexit(3) or on_exit(3), then it is called as many times as  it  was
       registered.

       All open stdio(3) streams are flushed and closed.  Files created by tmpfile(3) 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

       The exit() function does not return.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────┬───────────────┬─────────────────────┐
       │InterfaceAttributeValue               │
       ├──────────┼───────────────┼─────────────────────┤
       │exit()    │ Thread safety │ MT-Unsafe race:exit │
       └──────────┴───────────────┴─────────────────────┘
       The exit() function uses a global variable that is not protected, so it is not thread-safe.

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.

NOTES

       The behavior is undefined if one of the functions registered using atexit(3) and on_exit(3) calls  either
       exit()  or  longjmp(3).   Note that a call to execve(2) removes registrations created using atexit(3) and
       on_exit(3).

       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; 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) (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) 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) PR_SET_PDEATHSIG operation to arrange that it receives a signal
       if its parent terminates.

SEE ALSO

       _exit(2), get_robust_list(2), setpgid(2), wait(2), atexit(3), on_exit(3), tmpfile(3)

COLOPHON

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