Create child using fork() inside for loop to run execlp() - c

Question

I am writing a C program which will run Linux commands, like:
$ cat /etc/passwd | cut -f1 -d: | sort
The idea is to create child process using fork() to run the commands using execlp(). I planned to use two pipes for the communication and direct the input-output using dup().
The output is wrong:
ls -l | wc -c on command returns 1746
the program returns 1761
The code(edited to reflect suggestions):
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <limits.h>
int main()
{
int i,fd1[2],status,listpid[2];
pid_t child;
pipe(fd1);
for(i=0; i< 2; i++)
{
printf("\ncreating child\n");
if((child = fork()) == -1)
{
perror("fork");
exit(EXIT_FAILURE);
}
else if(child == 0)
{
if(i == 0)
{
close(1); dup(fd1[1]);
close(fd1[0]);
close(fd1[1]);
printf("\nrunning ls -l\n");
fflush(stdout);
execlp("ls","ls","-l", (char *)NULL);
exit(EXIT_SUCCESS);
}
else if(i == 1)
{
close(0); dup(fd1[0]);
close(fd1[1]);
close(fd1[0]);
printf("\nrunning wc -c\n");
fflush(stdout);
execlp("wc","wc","-c", (char *)NULL);
exit(EXIT_SUCCESS);
}
}
else
{
listpid[i]=child;
}
}
close(fd1[0]);
close(fd1[1]);
for(i = 0; i < 2; i++)
{
waitpid(listpid[i], &status, 0);
if(WIFEXITED(status))
{
printf("\n[%d] TERMINATED (Status: %d)\n",listpid[i], WEXITSTATUS(status));
}
}
exit(EXIT_SUCCESS);
}

Answer 1

First you can't waitpid in the loop -- if the output of ls is big enough it ill fill the pipe, and so it won't finish until someone reads it: you must wait for both children after the for loop.
Second -- the wc will go on for as long as the other end of the pipe is open, ie you will have to close the pipe in the parent as well.

Answer 2

After your update, the two child processes are behaving correctly. However, you still need to add:
close(fd1[0]);
close(fd1[1]);
between the for loop that launches the children and the for loop that collects the exit statuses.
Because the write end of the pipe is still open, wc does not receive EOF, so it doesn't terminate, so your process is waiting indefinitely.