I want to have one parent with 2 children.
The parent reads from file "a.txt" and sends trough pipe to first child; the first child reads the chars and sends to the second child the lower letter chars.
The second child prints in "b.txt" each distinct char and number of appearances(per line) and then sends trough a pipe to the parent the number of distinct chars. The parent prints the result from the second child.
I've done the pipe from parent to 1 child and to test I've put a pipe back to the parent.
What I can't figure it out is how to make the pipe go to the second child. I've been searching for information on dup2
but I don't get on how to make it work.
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <ctype.h>
#include <fcntl.h>
void main()
{
int pfd1[2], pfd2[2], pid1, pid2, pfin, status, fd;
char *c = (char *)malloc(sizeof(char));
if (pipe(pfd1) < 0) {
printf("Eroare la crearea pipe-ului\n");
exit(1);
}
if (pipe(pfd2) < 0) {
printf("Eroare la crearea pipe-ului\n");
exit(1);
}
if ((pid1 = fork()) < 0) {
printf("Eroare la fork\n");
exit(1);
}
if (pid1 == 0) { /*child */
close(pfd1[1]);
while (read(pfd1[0], c, 1) > 0) {
//printf("%s",c);
if (islower(*c)) {
close(pfd2[0]);
//inchid capul de citire; scriu in pipe
write(pfd2[1], c, 1);
////dup??????
}
}
printf("\n");
write(pfd[1], buff, len);
close(pfd1[0]);
close(pfd2[1]);
exit(0);
}
if ((pid2 = fork()) < 0) {
printf("Eroare la fork\n");
exit(1);
}
if (pid2 == 0) {
printf("second child");
exit(0);
}
/* parent */
close(pfd1[0]);
close(pfd2[1]);
fd = open("date.txt", O_RDONLY);
while (read(fd, c, 1) > 0) {
write(pfd1[1], c, 1);
}
close(pfd1[1]); /* la sfarsit inchide si capatul utilizat */
close(pfin);
while (read(pfd2[0], c, 1) > 0)
printf("%s", c);
close(pfd2[0]);
printf("%d", wait(&status));
printf("%d", wait(&status));
}
Thank you for your answers. Here is the code for the whole problem.