/* dup.c
 *
 * Parent piping to a child where child spawns using new stdin
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <wait.h>

extern char **environ;

int main(int argc, char **argv)
{
    pid_t pid;
    int stat_loc;

    char *str = "all base are belong to us";
    int pfds[2];
    int ret;

    if (pipe(pfds) == 0)
    {
        pid = fork();
        if (pid == -1)
        {
            perror("fork");
            exit(EXIT_FAILURE);
        }

        if (pid) /* parent */
        {
            close(1);         /* break the link to stdout, dup2 already kills this but meh */
            dup2(pfds[1], 1); /* redirect stdout to pfds[1] */
            close(pfds[1]);   /* new stdout has been setup above, pfds[1] can be closed */
            close(pfds[0]);   /* parent will not be reading anything from out pipe */

            printf("parent sends out: \"%s\"\n", str);
            fflush(stdout);   /* printf is buffered! */
            close(1);         /* close stdin or else the child would not know that he's done reading */

            ret = waitpid(pid, &stat_loc, WCONTINUED);
        }
        else /* child */
        {
            close(0);         /* break the link to stdin */
            dup2(pfds[0], 0); /* redirect stdin to pfds[0] */
            close(pfds[0]);   /* new stdin has been setup above, pfds[1] can be closed */
            close(pfds[1]);   /* parent will not be writing anything into our pipe */

            /* here the child will use a redefined stdin */
            execlp("wc", "wc", NULL);
            /* if there wasn't a spawn then we would need to close stdin */
        }
    }
    else
    {
        perror("pipe");
        exit(EXIT_FAILURE);
    }

    ret = ret; /* hush the dumb compiler */

    close(pfds[0]);
    close(pfds[1]);

    return 0;
}