freebsd-dev/lib/libc/stdlib/atexit.3

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.\"     @(#)atexit.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd September 6, 2002
.Dt ATEXIT 3
.Os
.Sh NAME
.Nm atexit
.Nd register a function to be called on exit
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft int
.Fn atexit "void (*function)(void)"
.Ft int
.Fn atexit_b "void (^function)(void)"
.Sh DESCRIPTION
The
.Fn atexit
function
registers the given
.Fa function
to be called at program exit, whether via
.Xr exit 3
or via return from the program's
.Fn main .
Functions so registered are called in reverse order;
no arguments are passed.
.Pp
These functions must not call
.Fn exit ;
if it should be necessary to terminate the process while in such a
function, the
.Xr _exit 2
function should be used.
(Alternatively, the function may cause abnormal
process termination, for example by calling
.Xr abort 3 . )
.Pp
At least 32 functions can always be registered,
and more are allowed as long as sufficient memory can be allocated.
.Pp
The
.Fn atexit_b
function behaves identically to
.Fn atexit ,
except that it takes a block, rather than a function pointer.
.\" XXX {ATEXIT_MAX} is not implemented yet
.Sh RETURN VALUES
.Rv -std atexit
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ENOMEM
No memory was available to add the function to the list.
The existing list of functions is unmodified.
.It Bq Er ENOSYS
The
.Fn atexit_b
function was called by a program that did not supply a
.Fn _Block_copy
implementation.
.El
.Sh SEE ALSO
.Xr at_quick_exit 3 ,
.Xr exit 3
.Sh STANDARDS
The
.Fn atexit
function
conforms to
.St -isoC .