freebsd-nq/lib/libc/stdlib/exit.3
Konstantin Belousov ee62fb2e1e _Exit(3): document implementation
Remove a useless note about unlinking temporary files, they are unlinked
in tmpfile(3) [1].  Add a note about __cxa_atexit().

Explain exactly what are the FreeBSD implementation differences between
exit() and _Exit().

Noted by:	markj [1]
Reviewed by:	emaste, markj
Sponsored by:	The FreeBSD Foundation
MFC after:	3 days
Differential revision:	https://reviews.freebsd.org/D31425
2021-08-08 22:39:46 +03:00

147 lines
3.9 KiB
Groff

.\" Copyright (c) 1990, 1991, 1993
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.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
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.\" @(#)exit.3 8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd August 5, 2021
.Dt EXIT 3
.Os
.Sh NAME
.Nm exit , _Exit
.Nd perform normal program termination
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft void
.Fn exit "int status"
.Ft void
.Fn _Exit "int status"
.Sh DESCRIPTION
The
.Fn exit
and
.Fn _Exit
functions terminate a process.
.Pp
Before termination,
.Fn exit
performs the following functions in the order listed:
.Bl -enum -offset indent
.It
Call all functions registered with the
.Xr __cxa_atexit 3
function
(which are typically destructors from the loaded dynamic objects),
and the functions registered with the
.Xr atexit 3
function, in the reverse order of their registration.
.It
Flush all open output streams.
.It
Close all open streams.
.El
.Pp
The
.Fn _Exit
function terminates without calling the functions registered with the
.Xr atexit 3
function, and may or may not perform the other actions listed.
The
.Fx
implementation of the
.Fn _Exit
function does not call destructors registered with
.Xr __cxa_atexit 3,
does not flush buffers, and does not close streams.
.Pp
Both functions make the low-order eight bits of the
.Fa status
argument available to a parent process which has called a
.Xr wait 2 Ns -family
function.
.Pp
The C Standard
.Pq St -isoC-99
defines the values
.Li 0 ,
.Dv EXIT_SUCCESS ,
and
.Dv EXIT_FAILURE
as possible values of
.Fa status .
Cooperating processes may use other values;
in a program which might be called by a mail transfer agent, the
values described in
.Xr sysexits 3
may be used to provide more information to the parent process.
.Pp
Note that
.Fn exit
does nothing to prevent bottomless recursion should a function registered
using
.Xr atexit 3
itself call
.Fn exit .
Such functions must call
.Fn _Exit
instead (although this has other effects as well which may not be desired).
.Sh RETURN VALUES
The
.Fn exit
and
.Fn _Exit
functions
never return.
.Sh SEE ALSO
.Xr _exit 2 ,
.Xr abort2 2 ,
.Xr wait 2 ,
.Xr at_quick_exit 3 ,
.Xr atexit 3 ,
.Xr intro 3 ,
.Xr quick_exit 3 ,
.Xr sysexits 3 ,
.Xr tmpfile 3
.Sh STANDARDS
The
.Fn exit
and
.Fn _Exit
functions conform to
.St -isoC-99 .
.Sh HISTORY
The
.Fn exit
function appeared in
.At v1 .