| .\" This manpage is Copyright (C) 1992 Drew Eckhardt; |
| .\" and Copyright (C) 1993 Michael Haardt, Ian Jackson. |
| .\" |
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| .\" Modified Wed Jul 21 23:02:38 1993 by Rik Faith <faith@cs.unc.edu> |
| .\" Modified 2001-11-17, aeb |
| .\" |
| .TH _EXIT 2 2021-03-22 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| _exit, _Exit \- terminate the calling process |
| .SH SYNOPSIS |
| .nf |
| .B #include <unistd.h> |
| .PP |
| .BI "noreturn void _exit(int " status ); |
| .PP |
| .B #include <stdlib.h> |
| .PP |
| .BI "noreturn void _Exit(int " status ); |
| .fi |
| .PP |
| .RS -4 |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .RE |
| .PP |
| .BR _Exit (): |
| .nf |
| _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L |
| .fi |
| .SH DESCRIPTION |
| .BR _exit () |
| terminates the calling process "immediately". |
| Any open file descriptors belonging to the process are closed. |
| Any children of the process are inherited by |
| .BR init (1) |
| (or by the nearest "subreaper" process as defined through the use of the |
| .BR prctl (2) |
| .B PR_SET_CHILD_SUBREAPER |
| operation). |
| The process's parent is sent a |
| .B SIGCHLD |
| signal. |
| .PP |
| The value |
| .I "status & 0xFF" |
| is returned to the parent process as the process's exit status, and |
| can be collected by the parent using one of the |
| .BR wait (2) |
| family of calls. |
| .PP |
| The function |
| .BR _Exit () |
| is equivalent to |
| .BR _exit (). |
| .SH RETURN VALUE |
| These functions do not return. |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. |
| The function |
| .BR _Exit () |
| was introduced by C99. |
| .SH NOTES |
| For a discussion on the effects of an exit, the transmission of |
| exit status, zombie processes, signals sent, and so on, see |
| .BR exit (3). |
| .PP |
| The function |
| .BR _exit () |
| is like |
| .BR exit (3), |
| but does not call any |
| functions registered with |
| .BR atexit (3) |
| or |
| .BR on_exit (3). |
| Open |
| .BR stdio (3) |
| streams are not flushed. |
| On the other hand, |
| .BR _exit () |
| does close open file descriptors, and this may cause an unknown delay, |
| waiting for pending output to finish. |
| If the delay is undesired, |
| it may be useful to call functions like |
| .BR tcflush (3) |
| before calling |
| .BR _exit (). |
| Whether any pending I/O is canceled, and which pending I/O may be |
| canceled upon |
| .BR _exit (), |
| is implementation-dependent. |
| .SS C library/kernel differences |
| In glibc up to version 2.3, the |
| .BR _exit () |
| wrapper function invoked the kernel system call of the same name. |
| Since glibc 2.3, the wrapper function invokes |
| .BR exit_group (2), |
| in order to terminate all of the threads in a process. |
| .PP |
| The raw |
| .BR _exit () |
| system call terminates only the calling thread, and actions such as |
| reparenting child processes or sending |
| .B SIGCHLD |
| to the parent process are performed only if this is |
| the last thread in the thread group. |
| .\" _exit() is used by pthread_exit() to terminate the calling thread |
| .SH SEE ALSO |
| .BR execve (2), |
| .BR exit_group (2), |
| .BR fork (2), |
| .BR kill (2), |
| .BR wait (2), |
| .BR wait4 (2), |
| .BR waitpid (2), |
| .BR atexit (3), |
| .BR exit (3), |
| .BR on_exit (3), |
| .BR termios (3) |