/* +-----------------------------------------------+
   | 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()
// indents are 3 spaces, because I find it aesthetically pleasing.
int main(int argc, char **argv) {
   // First we fork, and assign the child's pid to a variable
   int child = fork();                                          //! 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();                                       //! 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);                         //! wait(...)
      printf("[PARENT]: child %d exited. Status: %d.\n", exited_child, status);
      // exit
      exit(EXIT_SUCCESS);                                       //! exit(...)
   }
   // If we have no child, we are the child, and must execute
   else {
      // Get our pid, get parent's pid
      int pid = getpid(), parent = getppid();                   //! get[p]pid()
      // Print that information
      printf("[CHILD ]: pid = %d, parent_pid = %d\n", pid, parent);
      /* Prepare to hand over 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);              //! execl(...)
   }
}