Q61609: Specific Status of Process ID and CWAIT

Article: Q61609
Product(s): See article
Version(s): 5.10 6.00
Operating System(s): OS/2
Keyword(s): ENDUSER | | mspl13_c
Last Modified: 29-MAY-1990

Question:

I spawned a child process under OS/2 using the following code:

     pid = spawnve(P_NOWAITO,...parameter list...)
          if (pid != -1)
               status = cwait(&termstat, pid, WAIT_CHILD);

Why does CWAIT always return status==-1 and with errno set to ECHILD
even though the child runs successfully?

Response:

If not NULL, <termstat> points to a buffer that will contain a
termination-status word and return code for the child process. The
status word indicates whether the child terminated normally by calling
the OS/2 DosExit function.

When errno is set to ECHILD it is defined as follows:

   ECHILD   No child process.

            A wait was attempted by a thread that has no child
            processes, or whose child process had the no-wait option
            specified.

In this case, the garbage value for TERMSTAT was generated by using
P_NOWAITO rather than P_NOWAIT. In other words, the original spawn()
call made the cwait() call fail. We document P_NOWAIT and P_NOWAITO as
follows:

   P_NOWAIT Continues to execute parent process concurrently with child
            process.

   P_NOWAITO Continues to execute parent process and ignores wait and
             cwait calls against child process.

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