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diff --git a/man3/atexit.3 b/man3/atexit.3 new file mode 100644 index 0000000..4a57ac5 --- /dev/null +++ b/man3/atexit.3 @@ -0,0 +1,170 @@ +'\" t +.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) +.\" +.\" SPDX-License-Identifier: Linux-man-pages-copyleft +.\" +.\" References consulted: +.\" Linux libc source code +.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) +.\" 386BSD man pages +.\" Modified 1993-03-29, David Metcalfe +.\" Modified 1993-07-24, Rik Faith (faith@cs.unc.edu) +.\" Modified 2003-10-25, Walter Harms +.\" +.TH atexit 3 2023-07-20 "Linux man-pages 6.05.01" +.SH NAME +atexit \- register a function to be called at normal process termination +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <stdlib.h> +.PP +.BI "int atexit(void (*" function )(void)); +.fi +.SH DESCRIPTION +The +.BR atexit () +function registers the given +.I function +to be +called at normal process termination, either via +.BR exit (3) +or via return from the program's +.IR main (). +Functions so registered are called in +the reverse order of their registration; no arguments are passed. +.PP +The same function may be registered multiple times: +it is called once for each registration. +.PP +POSIX.1 requires that an implementation allow at least +.\" POSIX.1-2001, POSIX.1-2008 +.B ATEXIT_MAX +(32) such functions to be registered. +The actual limit supported by an implementation can be obtained using +.BR sysconf (3). +.PP +When a child process is created via +.BR fork (2), +it inherits copies of its parent's registrations. +Upon a successful call to one of the +.BR exec (3) +functions, +all registrations are removed. +.SH RETURN VALUE +The +.BR atexit () +function returns the value 0 if successful; otherwise +it returns a nonzero value. +.SH ATTRIBUTES +For an explanation of the terms used in this section, see +.BR attributes (7). +.TS +allbox; +lbx lb lb +l l l. +Interface Attribute Value +T{ +.na +.nh +.BR atexit () +T} Thread safety MT-Safe +.TE +.sp 1 +.SH VERSIONS +POSIX.1 says that the result of calling +.\" POSIX.1-2001, POSIX.1-2008 +.BR exit (3) +more than once (i.e., calling +.BR exit (3) +within a function registered using +.BR atexit ()) +is undefined. +On some systems (but not Linux), this can result in an infinite recursion; +.\" This can happen on OpenBSD 4.2 for example, and is documented +.\" as occurring on FreeBSD as well. +.\" glibc does "the Right Thing" -- invocation of the remaining +.\" exit handlers carries on as normal. +portable programs should not invoke +.BR exit (3) +inside a function registered using +.BR atexit (). +.SH STANDARDS +C11, POSIX.1-2008. +.SH HISTORY +POSIX.1-2001, C89, C99, SVr4, 4.3BSD. +.SH NOTES +Functions registered using +.BR atexit () +(and +.BR on_exit (3)) +are not called if a process terminates abnormally because +of the delivery of a signal. +.PP +If one of the registered functions calls +.BR _exit (2), +then any remaining functions are not invoked, +and the other process termination steps performed by +.BR exit (3) +are not performed. +.PP +The +.BR atexit () +and +.BR on_exit (3) +functions register functions on the same list: +at normal process termination, +the registered functions are invoked in reverse order +of their registration by these two functions. +.PP +According to POSIX.1, the result is undefined if +.BR longjmp (3) +is used to terminate execution of one of the functions registered using +.BR atexit (). +.\" In glibc, things seem to be handled okay +.SS Linux notes +Since glibc 2.2.3, +.BR atexit () +(and +.BR on_exit (3)) +can be used within a shared library to establish functions +that are called when the shared library is unloaded. +.SH EXAMPLES +.\" SRC BEGIN (atexit.c) +.EX +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +\& +void +bye(void) +{ + printf("That was all, folks\en"); +} +\& +int +main(void) +{ + long a; + int i; +\& + a = sysconf(_SC_ATEXIT_MAX); + printf("ATEXIT_MAX = %ld\en", a); +\& + i = atexit(bye); + if (i != 0) { + fprintf(stderr, "cannot set exit function\en"); + exit(EXIT_FAILURE); + } +\& + exit(EXIT_SUCCESS); +} +.EE +.\" SRC END +.SH SEE ALSO +.BR _exit (2), +.BR dlopen (3), +.BR exit (3), +.BR on_exit (3) |