/* +-----------------------------------------------+
   | John Breaux - jab0910 - JohnBreaux@my.unt.edu |
   |  syscalls.c - CSCE4600 Homework 1 Question 2  |
   +-----------------------------------------------+ */

#include <sys/wait.h> // wait()
#include <unistd.h>   // fork(), getpid(), getppid(), execl(), exit()
#include <stdlib.h>   // EXIT_SUCCESS
#include <stdio.h>    // printf()
// tabs are 3 spaces, because I find it more aesthetically pleasing than x=[1-8]|x!=3 spaces
int main(int argc, char **argv) {
   // First we fork, and assign the child's pid to a variable
   int child = fork();
   // If we have a child, then we're the parent, and must wait for the child to execute
   if (child) {
      // We get our own pid
      int pid = getpid();
      printf("[PARENT]: pid = %d, child = %d\n", pid, child);
      // Wait for the child to exit, and acquire its status
      int status = 0;
      int exited_child = wait(&status);
      printf("[PARENT]: child %d exited with status %d.\n", exited_child, status);
      // exit
      exit(EXIT_SUCCESS);
   }
   // If we have no child, we are the child, and are assigned the task of executing
   else {
      // Get our pid, get parent's pid
      int pid = getpid(), parent_pid = getppid();
      // Print that information
      printf("[CHILD ]: pid = %d, parent_pid = %d\n", pid, parent_pid);
      // Hand control over to ls, with the arguments "-la"
      char *command = "/bin/ls", *argv1 = "-la";
      printf("[CHILD ]: execl(%s, %s, NULL);\n", command, argv1);
      // execl takes the command, the arguments, and a null-pointer terminator argument
      // argv[0] is the path to the command, argv[1] is the first argument
      // personally I prefer execv()/execve() for their relative ease of use
      execl(command, command, argv1, (char*)NULL);
   }
}