Linux C gets the implementation code for the process exit value

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <errno.h>
int main(int argc, char *argv[])
{
 pid_t pid;
 int stat;
 int exit_code;

 pid = fork();
 if(pid == 0)
 {
  sleep(3);
  exit(5);
 }
 else if( pid < 0 )
 {
  fprintf(stderr, "fork failed: %s", strerror(errno));
  return -1;
 }

 wait(&stat); //Wait for a child process to finish
 if(WIFEXITED(stat)) //WIFEXITED() returns true if the child process ends normally by return, exit, _exit
 {
  exit_code = WEXITSTATUS(stat);
  printf("child's exit_code: %dn", exit_code);
 }

 return 0;
}