.\" Copyright (c) 2004 Apple Computer, Inc.
.\"
.Dd August 12, 2004
.Dt PTHREAD_ATFORK 3
.Os
.Sh NAME
.Nm pthread_atfork
.Nd register handlers to be called before and after
.Fn fork
.Sh SYNOPSIS
.Fd #include <pthread.h>
.Ft int
.Fn pthread_atfork "void (*prepare)(void)" "void (*parent)(void)" "void (*child)(void)"
.Sh DESCRIPTION
The
.Fn pthread_atfork
function is used to register functions to be called before and after
.Fn fork .
The
.Fa prepare 
handler is called before
.Fn fork ,
while the
.Fa parent
and
.Fa child
handlers are called after
.Fn fork
in the parent and child process respectively.
The
.Fa prepare
handlers are called in reverse order of their registration, while
.Fa parent
and
.Fa child
handlers are called in the order in which they were registered.
Any of the handlers may be NULL.
.Pp
.Em Important :
only async-signal-safe functions are allowed on the child side of
.Fn fork .
See
.Xr sigaction 2
for details.
.Sh RETURN VALUES
If successful, the
.Fn pthread_atfork
function will return zero; otherwise an error number will be returned to
indicate the error.
.Sh ERRORS
.Fn pthread_atfork
will fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
The system lacked the necessary resources to add another handler to the list.
.El
.Sh SEE ALSO
.Xr fork 2
.Sh STANDARDS
.Fn pthread_atfork
conforms to
.St -p1003.1-96 .