вызвать нормальное завершение процесса (cause normal process termination)
Имя (Name)
exit - cause normal process termination
Синопсис (Synopsis)
#include <stdlib.h>
noreturn void exit(int status);
Описание (Description)
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)).
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.
Возвращаемое значение (Return value)
The exit() function does not return.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────┬───────────────┬─────────────────────┐
│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.
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
Примечание (Note)
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 (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) (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.
Смотри также (See also)
_exit(2), get_robust_list(2), setpgid(2), wait(2), atexit(3),
on_exit(3), tmpfile(3)
