term% cat index.txt EXITS(2) System Calls Manual 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 indi‐
cate normal termination. The string is passed to the parent process,
prefixed by the name and process 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 argument 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 reached.
Atexitdont cancels a previous registration of an exit function.
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 routines. Terminate is called automati‐
cally 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 ter‐
minates 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)
EXITS(2)