Programming

scanner_pid = fork();
    int scannertoeven[2]; int scannertoodd[2]; int eventoscanner[2]; int oddtoscanner[2];
     pid_t even_pid, odd_pid, scanner_pid;


     //We need the scanner pid so even and odd can send signals to it
     char pidofparent[sizeof(scanner_pid)];
     sprintf(pidofparent, "%i", scanner_pid);
   
     //Scanner
     if (scanner_pid  == 0) {

          //Scanner writes to even and odd- uncommenting these screws things up
          //dup2(scannertoodd[1], STDOUT_FILENO);
          //dup2(scannertoeven[1], STDOUT_FILENO);

          close(scannertoeven[0]); close(scannertoeven[1]);
          close(eventoscanner[0]); close(eventoscanner[1]);
          close(scannertoodd[0]); close(scannertoodd[1]);
          close(oddtoscanner[0]); close(oddtoscanner[1]);

          if(execl("./scanner", "scanner", stoeven, stoodd, eventos, oddtos, NULL ) == -1) {
               printf("execl Error!");
               exit(1);
          }

          exit(0);
          
     //Even 
     } else if ((even_pid = fork()) == 0) {
          //Even reads from scanner
          dup2(scannertoeven[0], STDIN_FILENO);
          //Even writes to scanner
          dup2(eventoscanner[1], STDOUT_FILENO);

          close(scannertoeven[0]); close(scannertoeven[1]);
          close(eventoscanner[0]); close(eventoscanner[1]);
          close(scannertoodd[0]); close(scannertoodd[1]);
          close(oddtoscanner[0]); close(oddtoscanner[1]);
          
          //Execute evenodd as even
          if(execl("./evenodd", "even", pidofparent,  NULL ) == -1) {
               printf("execl Error!");
               exit(1);
          }
          exit(0);

     //Odd
     } else if ((odd_pid = fork()) == 0){
          //Odd reads from scanner
          dup2(scannertoodd[0], STDIN_FILENO);
          //Odd reads from scanner
          dup2(oddtoscanner[1], STDOUT_FILENO);

          // Not sure which ones to close
          close(scannertoeven[0]); close(scannertoeven[1]);
          close(eventoscanner[0]); close(eventoscanner[1]);
          close(scannertoodd[0]); close(scannertoodd[1]);
          close(oddtoscanner[0]); close(oddtoscanner[1]);

          if(execl("./evenodd", "odd", pidofparent,  NULL ) == -1) {
               printf("execl Error!");
               exit(1);
          } 
          exit(0);
          
     //Main
     } else {
          //Close Pipes- all of them
          close(scannertoodd[0]); close(scannertoeven[0]); close(eventoscanner[0]); close(oddtoscanner[0]);
          close(scannertoodd[1]); close(scannertoeven[1]); close(eventoscanner[1]); close(oddtoscanner[1]);

          //Wait for children to finish
          waitpid(scanner_pid, &status1, 0);
          waitpid(odd_pid, &status2, 0);
          waitpid(even_pid, &status3, 0);
          printf("\nAll processes terminated successfully\n");
     }

//Send to odd
                    if ((length & 1) == 1) {
                         write(scannertoodd, w, (strlen(w) + 1));
                    //Send to even
                    } else {                 
                         write(scannertoeven, w, (strlen(w) + 1));

int main(void)
{
        pid_t childa, childb;
        int apipein[2], apipeout[2];
        int bpipein[2], bpipeout[2];

        pipe(apipein); pipe(apipeout);
        pipe(apipein); pipe(apipeout);

        childa=fork();
        if(childa == 0) // Child code
        {
                int n;
                dup2(apipein[0], STDIN_FILENO);
                dup2(apipeout[1], STDOUT_FILENO);

                for(n=0; n<2; n++)
                {
                        close(apipein[n]); close(apipeout[n]);
                        close(bpipein[n]); close(bpipeout[n]);
                }

                exec(...);
                exit(1); // If we get here, exec failed, therefore return error!
        }

        childb=fork();
        if(childb == 0)
        {
                dup2(bpipein[0], STDIN_FILENO);
                dup2(bpipeout[1], STDOUT_FILENO);

                for(n=0; n<2; n++)
                {
                        close(apipein[n]); close(apipeout[n]);
                        close(bpipein[n]); close(bpipeout[n]);
                }

                exec(...);
                exit(1);
        }

        // Close all ends of the pipes we're not using
        close(apipein[0]); close(bpipein[0]);
        close(apipeout[1]); close(bpipeout[1]);
}

int scannertoeven[2]; int scannertoodd[2]; int eventoscanner[2]; int oddtoscanner[2];
pid_t even_pid, odd_pid, scanner_pid;
if (pipe(scannertoeven) || (pipe(eventoscanner))) { fprintf(stderr, "Pipe error bewteen scanner and even!\n"); exit(1); }
if ((pipe(scannertoodd) || (pipe(oddtoscanner)))) { fprintf(stderr, "Pipe error between scanner and odd!\n"); exit(1); }