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.TH ATEXIT 3C "May 25, 2001"
.SH NAME
atexit \- register a function to run at process termination or object unloading
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBatexit\fR(\fBvoid (*\fR\fIfunc\fR)(void));
.fi

.SH DESCRIPTION
.sp
.LP
The \fBatexit()\fR function registers the function pointed to by \fIfunc\fR to
be called without arguments on normal termination of the program or when the
object defining the function is unloaded.
.sp
.LP
Normal termination occurs by either a call to the \fBexit\fR(3C) function or a
return from \fBmain()\fR. Object unloading occurs when a call to
\fBdlclose\fR(3C) results in the object becoming unreferenced.
.sp
.LP
The number of functions that may be registered with \fBatexit()\fR is limited
only by available memory (refer to the \fB_SC_ATEXIT_MAX\fR argument of
\fBsysconf\fR(3C)).
.sp
.LP
After a successful call to any of the \fBexec\fR(2) functions, any functions
previously registered by \fBatexit()\fR are no longer registered.
.sp
.LP
On process exit, functions are called in the reverse order of their
registration. On object unloading, any functions belonging to an unloadable
object are called in the reverse order of their registration.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, the \fBatexit()\fR function returns 0. Otherwise,
it returns a non-zero value.
.SH ERRORS
.sp
.LP
The \fBatexit()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
Insufficient storage space is available.
.RE

.SH USAGE
.sp
.LP
The functions registered by a call to \fBatexit()\fR must return to ensure that
all registered functions are called.
.sp
.LP
There is no way for an application to tell how many functions have already been
registered with \fBatexit()\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR exec (2),
.BR dlclose (3C),
.BR exit (3C),
.BR sysconf (3C),
.BR attributes (7)