Various programs connect via pipes

aliz2000 · #1 18-May-2009, 08:50

Hi all,

i am currently stuck on my program

my program basically connects prog1 > prog2 > prog3.
this will be done using pipes.

output of prog1> input prog2 output > input prog3

my program just basically hangs when i try to run it.

if anyone could point me in the right direction would be great, i have been stuck on this for dayyss.

am i going about this the correct way. any help would be great.

here is my code:

CPP / C++ / C Code:


#include <ctype.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/wait.h>
main()
{ 


int p_des[2];
int p_des2[2];
pipe( p_des ); /* The pipe descriptor */
pipe( p_des2 );


           if ( fork () == 0 )
           {


              dup2(p_des[1], 1);
              close(p_des[0]); /* process-A closing read end of the pipe */

              execlp("./task1", "task1", 0);
                 /*** exit(1); ***/
          }

else
if ( fork () == 0 )
           { 

           dup2(p_des2[1],1);
           close(p_des2[0]);  



           dup2(p_des[0], 0);
           close(p_des[1]);  
           execlp("./task2", "task2", 0);

        }


else
if ( fork () == 0 )
        { 


         dup2(p_des[0], 0);
         close(p_des[1]); /* process-B closing write end of the pipe */

         execlp("./task3", "task3", 0);
         /*** exit(1); ****/
       }

else
{ 
     close(p_des[1]); /* parent closing both the ends of pipe */
     close(p_des[0]);
     close(p_des2[1]); /* parent closing both the ends of pipe */
     close(p_des2[0]);

    wait(0);
    wait(0);
    wait(0);
 }
fflush(stdout);
}

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