/*
    exectest.c
    
    Started by Jeff Ondich on 3/26/96
    Last modified 16 February 2022
    Modified by Tanya Amert for Fall 2023
    
    This program gives a simple example of
    exec, and how a parent process can wait for
    a child process to return.

    Documentation for exec* calls: https://linux.die.net/man/3/exec.
*/

#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

// A simple demonstration of fork() + execlp() + wait().
int main(int argc, char *argv[])
{
    pid_t pid = fork();

    if (pid == 0)
    {
        /* Child */
        printf("Process %d is about to execute a program\n", getpid());
        fflush(stdout);

        // Choose one of these, and comment the other out:
        execlp("getanumber", "getanumber", (char *)0);
        // execlp("ls", "ls", "-l", (char *)0);

        // Check for errors (https://cplusplus.com/reference/cstdio/perror)
        perror("exec failed");
        fflush(stdout);
    }
    else
    {
        /* Parent */
        printf("Parent just created child, ID %d\n", pid);
        fflush(stdout);

        // Wait for the child to finish execution
        int status;
        pid = wait(&status);
        printf("My child ID %d just exited with status %d\n", pid, WEXITSTATUS(status));
        fflush(stdout);
    }

    return 0;
}