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

     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)