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Full Discussion: Pipelining Processes
Top Forums Programming Pipelining Processes Post 63095 by Trivialnight on Tuesday 22nd of February 2005 04:11:38 PM
Old 02-22-2005
Pipelining Processes
I am doing a program that will calculate the 199th fibonacci number using pipelines and multiple processes for each calculation. I have figured everything out except why none of the processes before the last one never execute the findfib() function;

Our teacher gave us the pipeline code to redirect stdin and stdout, but even when i execute the example file he gave us with it. It still is just running the findfib function at the last process only, I would go ask him about it but today he doesn't have any office hours. All the right headers are there. I have written the code for calculate the numbers using strings and whatnot but this is the only thing that is holding me back from completing. It seems as though the child never equals the parent which makes it not go into the if parent parent.

Code:
int
main(int argc, char *argv[])
{
   int i,nproc;
   if(chkargs(argc,argv) == 0) exit(1);
   nproc = strtol(argv[1],0,0);
   mkpipeln(&i,nproc);
   findfib(i,nproc);
   exit(0);
}

void
mkpipeln(int *id, int np)
{  int fd[2]; pid_t child;
   for(*id = 1; *id < np; (*id)++) {
       if(pipe(fd) < 0) die("pipe-1 failed");
       if((child = fork()) < 0) die("fork failed");
       if(child > 0){

         if(dup2(fd[1],1) < 0) die("dup2-1 failed");
         if((close(fd[0]) < 0) || (close(fd[1]) < 0)) die("close-1 failed");
         break;
       }
       else{
         if(dup2(fd[0],0) < 0) die("dup2-2 failed");
         if((close(fd[0]) < 0) || (close(fd[1]) < 0)) die("close-2 failed");
       }
   }
   printf("id: %d\n", *id);
}

void
findfib(int id, int np)
{  printf("id: %d\n", id);
}

Now shouldn't it print out each ID in each process?

-tn
 

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LEARN ABOUT HPUX

setpriority

getpriority(2)							System Calls Manual						    getpriority(2)

NAME

       getpriority, setpriority - get or set process priority

SYNOPSIS

DESCRIPTION

       returns the priority of the indicated processes.

       sets the priority of the indicated processes to priority.

       The processes are indicated by which and who, where which can have one of the following values:

	      Get or set the priority of the specified process where
				  who is the process ID.  A who of implies the process ID of the calling process.

	      Get or set the priority of the specified process group where
				  who  is  the	process-group  ID, indicating all processes belonging to that process-group.  A who of implies the
				  process-group ID of the calling process.

	      Get or set the priority of the specified user where
				  who is the user ID, indicating all processes owned by that user.  A who of implies the user ID  of  the  calling
				  process.

       If  more  than  one  process is indicated, the value returned by is the lowest valued priority of all the indicated processes, and sets the
       priority of all indicated processes.

       priority is a value from to where lower values indicate better priorities.  The default priority for a process is 0.

       If the calling process contains more than one thread or lightweight process (i.e., the process is  multi-threaded)  these  functions  shall
       apply to all threads or lightweight processes in the calling process.  The priority specified (or retrieved) is the same for all threads or
       lightweight processes in a process.  Negative priorities require appropriate privileges.

   Security Restrictions
       These system calls are subject to compartmental restrictions which restrict their access to processes in other compartments.  This restric-
       tion covers for querying the priority of processes in other compartments, and for changing the priority of processes in other compartments.
       See compartments(5) for more information about compartmentalization on systems that support that feature.

       Compartmental restrictions can be overridden if the process has the privilege (PRIV_COMMALLOWED).  Processes owned by the superuser may not
       have this privilege.  Processes owned by any user may have this privilege, depending on system configuration.

       requires the privilege (PRIV_OWNER) to change the priority of a process whose uid does not match the caller's real or effective uid..  Pro-
       cesses owned by the superuser have this privilege.  Processes owned by other users may have this privilege, depending on system	configura-
       tion.

       requires  the  privilege (PRIV_LIMIT).  Processes owned by the superuser have this privilege.  Processes owned by other users may have this
       privilege, depending on system configuration.

RETURN VALUE

       returns the following values:

	      Successful completion.
		     n is an integer priority in the range to
	      Failure.
		     is set to indicate the error.  See WARNINGS below.

       returns the following values:

	      Successful completion.
	      Failure.
		     is set to indicate the error.

ERRORS

       If or fails, is set to one of the following values:

	      [EACCES]	     The calling process does not have access rights to change one or more of the indicated processes.	All processes  for
			     which access is allowed are still affected.

	      [EINVAL]	     which is not one of the choices listed above, or who is out of range.

	      [EPERM]	     The  calling  process attempted to change the priority of a process to a smaller priority value without having appro-
			     priate privileges.

	      [ESRCH]	     Processes indicated by which and who cannot be found.

WARNINGS

       can return both when it successfully finds a priority of and when it fails.  To determine whether a failure occurred, set to before calling
       then examine after the call returns.

AUTHOR

       and were developed by the University of California, Berkeley.

SEE ALSO

       nice(1), renice(1M), nice(2).

																    getpriority(2)
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