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+.\" This manpage is Copyright (C) 1992 Drew Eckhardt;
+.\"             and Copyright (C) 1993 Michael Haardt, Ian Jackson.
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.\" Modified Wed Jul 21 23:02:38 1993 by Rik Faith <faith@cs.unc.edu>
+.\" Modified 2001-11-17, aeb
+.\"
+.TH _exit 2 (date) "Linux man-pages (unreleased)"
+.SH NAME
+_exit, _Exit \- terminate the calling process
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
+.SH SYNOPSIS
+.nf
+.B #include <unistd.h>
+.P
+.BI "[[noreturn]] void _exit(int " status );
+.P
+.B #include <stdlib.h>
+.P
+.BI "[[noreturn]] void _Exit(int " status );
+.fi
+.P
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.P
+.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.
+.P
+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.
+.P
+The function
+.BR _Exit ()
+is equivalent to
+.BR _exit ().
+.SH RETURN VALUE
+These functions do not return.
+.SH STANDARDS
+.TP
+.BR _exit ()
+POSIX.1-2008.
+.TP
+.BR _Exit ()
+C11, POSIX.1-2008.
+.SH HISTORY
+POSIX.1-2001, SVr4, 4.3BSD.
+.P
+.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).
+.P
+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
+The text above in DESCRIPTION describes the traditional effect of
+.BR _exit (),
+which is to terminate a process,
+and these are the semantics specified by POSIX.1 and implemented
+by the C library wrapper function.
+On modern systems, this means termination of all threads in the process.
+.P
+By contrast with the C library wrapper function, the raw Linux
+.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
+.P
+Up to glibc 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.
+.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)