WAIT(II) 2/9/75 WAIT(II)





WAIT(II)                     2/9/75                      WAIT(II)







NAME

     wait - wait for process to terminate



SYNOPSIS

     (wait = 7.)

     sys  wait

     (process ID in r0)

     (status in r1)



     wait(status)

     int *status;



DESCRIPTION

     Wait causes its caller to  delay  until  one  of  its  child

     processes  terminates.  If any child has died since the last

     wait, return is immediate; if there are no children,  return

     is  immediate  with the error bit set (resp. with a value of

     -1 returned).  The normal return yields the  process  ID  of

     the  terminated  child  (in  r0).   In  the  case of several

     children several wait calls are needed to learn of  all  the

     deaths.



     If no error is indicated on return, the r1 high byte  (resp.

     the  high byte stored into status ) contains the low byte of

     the child process r0 (resp. the argument of exit )  when  it

     terminated.   The  r1 (resp.  status ) low byte contains the

     termination status of the process.  See signal  (II)  for  a

     list  of  termination statuses (signals); 0 status indicates

     normal termination.  A special status (0177) is returned for

     a  stopped  process  which  has  not  terminated  and can be

     restarted.  See  ptrace  (II).   If  the  0200  bit  of  the

     termination  status  is set, a core image of the process was

     produced by the system.



     If the parent process  terminates  without  waiting  on  its

     children,  the  initialization  process  (process  ID  =  1)

     inherits the children.



SEE ALSO

     exit (II), fork (II), signal (II)



DIAGNOSTICS

     The error bit (c-bit) is set if there are  no  children  not

     previously  waited  for.   From  C,  a  returned value of -1

     indicates an error.
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