term% ls -F
term% cat index.txt
EXITS(2)                      System Calls Manual                     EXITS(2)

       exits,  _exits,  atexit,  atexitdont,  terminate  -  terminate process,
       process cleanup

       #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)

       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.

       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.


       fork(2), wait(2)