#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/errno.h>


int do_parent(pid_t);
void do_child(int);


int main(void) {
    int devnul;
    pid_t pid;

    devnul = open("/dev/null", O_WRONLY);
    pid = fork();
    if (pid) {
        /* Parent */
        return do_parent(pid);
    } else {
        /* Child */
        do_child(devnul);
    }
}


int do_parent(pid_t child_pid) {
    FILE *f;
    char buf[120];
    char filename[20];

    printf("child pid: %d\n", child_pid);
    sleep(10);
    printf("sending SIGKILL\n");
    kill(child_pid, SIGKILL);
    sleep(10);
    sprintf(filename, "/proc/%d/stat", child_pid);
    printf("reading %s\n", filename);
    f = fopen(filename, "r");
    if (f == NULL) {
        printf("fopen error [%d]: %s\n", errno, strerror(errno));
        if (!access(filename, R_OK)) {
            printf("but the file exists and is readable\n");
        }
    } else {
        fread(buf, sizeof(char), 120, f);
        printf(buf);
    }
    return wait4(child_pid, NULL, 0, NULL);
}


void do_child(int out) {
    char *argv[2] = { "/usr/bin/yes", NULL };
    dup2(out, 1);
    execv(argv[0], argv);
    exit(0);
}