EXITS(2) EXITS(2)
NAME
exits, _exits, atexit, atexitdont, terminate - terminate
process, process cleanup
SYNOPSIS
#include <u.h>
#include <libc.h>
void _exits(char *msg)
void exits(char *msg)
int atexit(void(*)(void))
void atexitdont(void(*)(void))
/* Alef only */
void _exits(byte *msg)
void exits(byte *msg)
void terminate(byte *msg)
DESCRIPTION
Exits is the conventional way to terminate a process.
_Exits is the underlying system call. They can never
return.
Msg conventionally includes a brief (maximum length ERRLEN)
explanation of the reason for exiting, or a null pointer or
empty string to indicate normal termination. The string is
passed to the parent process, prefixed by the name and pro-
cess id of the exiting process, when the parent does a
wait(2).
Before calling _exits with msg as an argument, exits calls
in reverse order all the functions recorded by atexit.
Atexit records fn as a function to be called by exits. It
returns zero if it failed, nonzero otherwise. A typical use
is to register a cleanup routine for an I/O package. To
simplify programs that fork or share memory, exits only
calls those atexit-registered functions that were registered
by the same process as that calling exits.
Calling atexit twice (or more) with the same function argu-
ment causes exits to invoke the function twice (or more).
There is a limit to the number of exit functions that will
be recorded; atexit returns 0 if that limit has been
Page 1 Plan 9 (printed 12/21/24)
EXITS(2) EXITS(2)
reached.
Atexitdont cancels a previous registration of an exit func-
tion.
Alef
In Alef, the system call _exits is the same, but its use is
discouraged because the run-time system needs to maintain
consistency; terminate and exits are the recommended rou-
tines. Terminate is called automatically when a task or
proc returns from its main function; it may also be called
explicitly. In either case, it frees resources private to
the task (which may be the implicit main task within the
proc) and terminates that task. If that task is the last
one in the proc, resources private to the proc are then
freed. If that proc is the last one in the program, it
calls exits. Exits should only be called in the last proc of
a program; it calls any atexit functions (registered by any
proc) and then calls _exits.
In Alef, atexit and atexitdont behave the same as in C.
SOURCE
/sys/src/libc/port/atexit.c
SEE ALSO
fork(2), wait(2)
Page 2 Plan 9 (printed 12/21/24)