exit — cause normal process termination
#include <stdlib.h>
void
exit( |
int | status) ; |
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.
It is undefined what happens if one of the functions
registered using atexit(3) and on_exit(3) calls either
exit
() or longjmp(3).
The use of EXIT_SUCCESS and EXIT_FAILURE is slightly more portable (to non-Unix environments) than the use of 0 and some non-zero 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. If
the parent was waiting on the child it is notified of the
exit status. In both cases the exiting process dies
immediately. If the parent has not indicated that it is not
interested in the exit status, but is not waiting, the
exiting process turns into a "zombie" process (which is
nothing but a container for the single byte representing the
exit status) so that the parent can learn the exit status
when it later calls one of the wait(2) functions.
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.
If the 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.
_exit(2), wait(2), atexit(3), on_exit(3), tmpfile(3)
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