pipeforkdemo.c

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

#define CHILD_MESS "I want a cookie\n"
#define PAR_MESS "testing..\n"
#define oops(m, x) {perror(m); exit(x);}

int main()
{
    int pipefd[2];
    int len;
    char buf[BUFSIZ];
    int read_len;

    if(pipe(pipefd) == -1) {
        oops("can`t get a pipe", 1);
    }

    switch(fork()) {
        case -1:
            oops("can`t fork", 2);
        case 0:
            len = strlen(CHILD_MESS);
            while(1) {
                if( write(pipefd[1], CHILD_MESS, len) != len )
                    oops("write", 3);
                sleep(5);
            }
        default:
            len = strlen(PAR_MESS);
            while( 1 ) {
                if ( write(pipefd[1], PAR_MESS, len) != len )
                    oops("write", 4);
                sleep(1);
                read_len = read(pipefd[0], buf, BUFSIZ);
                if( read_len <= 0 )
                    break;
                printf("%s\n", buf);
            }
    }
}