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
       indicate 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; termi-
       nate and exits are the recommended routines.  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 (regis-
       tered 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)