Concurrency programming example: test user reflexes

reflexes.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/time.h>
#include <pthread.h>

void *listen(void *timestamp) {
  int c;
  while((c = getc(stdin)) != EOF) {
    if( c == '\n' ) {
      gettimeofday((struct timeval *)timestamp, NULL);
      break;
    }
  }

  return NULL;
}

int main(void) {
  pthread_t listener;
  struct timeval entered, paused, diff;

  if( pthread_create(&listener, NULL, listen, &entered) ) {
    fprintf(stderr, "Error: could not create keyboard listening thread\n");
    return 1;
  }

  srand(time(NULL));
  sleep(rand() % 10 + 1);
  printf("GO!\n");
  gettimeofday(&paused, NULL);

  if( pthread_join(listener, NULL) ) {
    fprintf(stderr, "Error: could not join keyboard listening thread\n");
    return 2;
  }

  if( timercmp(&paused, &entered, >) )
    printf("FAIL\n");
  else {
    timersub(&entered, &paused, &diff);
    printf("%ld\n", (1000LL * diff.tv_sec) + (diff.tv_usec / 1000));
  }

  return 0;
}