#: 11417 S12/OS9/68000 (OSK)
    20-Jul-91  21:09:29
Sb: #11412-forks and pipes
Fm: Bob van der Poel 76510,2203
To: Kevin Darling 76703,4227 (X)

Kevin,

Here's a bit of code. Remember, this is 'C' -- but since it just calls the
system F$Fork even die-hard assembler types like you should be able to help
:

First off, a bit of the section which starts the pipeline:

   char *argv[MAXARGS];
   FILE *out_file;
   int childnum, pipe, oldin, oldout, os9fork();
   extern char **environ;

   if((pipe=open("/pipe",S_IREAD+S_IWRITE))<0)
         terminate("Unable to open '/pipe'");;

   oldin=dup(0);   /* save current stdin/out */
   oldout=dup(1);

   close(0);        /* set stdin to new pipe file */
   dup(pipe);
   close(1);        /* set stdout to current output file */
   dup(fileno(out_file));

   argv[0]="shell";
   argv[1]=newprog;
   argv[2]=0;
   childnum=os9exec(os9fork,argv[0],argv,environ,0,0);

   close(0);       /* restore original stdin */
   dup  (oldin);
   close(oldin);

   close(1);        /* restore original stdout */
   dup  (oldout);
   close(oldout);

   if(childnum<0){      /* fork failure, close the pipe file */
      childnum=0;
      close(pipe);
      terminate("Unable to fork pipe process");
   }
   else{
      fclose(out_file);            /* close old output file */
      out_file=fdopen(pipe,"w");    /* set to pipefile */
   }

And here is the snippet which gives the problem.

   fclose(out_file);   /* close down the pipeline */

   /* wait for a pipe process to finish it's thing... */

   if(childnum){
      wait(0);
      childnum=0;
   }

Continued next message.