gistfile1.txt

/*
$ ./a
Parent: 76922
Child: 76923, trying to trace parent: 76922
ptrace: Operation not permitted
failed. Errno: 1
Parent: rip children
*/



#include <sys/ptrace.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

int main() {
    pid_t parent, child;

    parent = getpid();
    printf("Parent: %d\n", parent);

    child = fork();

    if (child == -1) {
        perror("fork");
        exit(EXIT_FAILURE);
    }

    if (child == 0) {
        printf("Child: %d, trying to trace parent: %d\n", getpid(), parent);

        if (ptrace(PTRACE_ATTACH, parent, NULL, NULL) == -1) {
            perror("ptrace");
            printf("failed. Errno: %d\n", errno);
        } else {
            printf("child did the thing!\n");
            ptrace(PTRACE_DETACH, parent, NULL, NULL);
        }
        exit(EXIT_SUCCESS);
    } else {
        wait(NULL); 
        printf("Parent: rip children\n");
    }

    return 0;
}