threading code listing from multi-threading series on YT

threads_1.c

#include <pthread.h>  // for POSIX threads
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>  // for pause and sleep

void *thread_routine(void *arg) {
  char *thread_id = (char *)arg;

  while (1) {
    printf("%s\n", thread_id);
    sleep(3);
  }
}

void thread_create() {
  // opaque object
  pthread_t thread;

  // you can pass state to a thread
  // but you CANNOT pass caller's local state OR stack memory
  // MUST be heap or static because ea thread has its own stack (part of the
  // exec ctx)
  static char *thread_arg = "thread 1";

  // pthread does NOT use errno
  // all pthread functions return special error codes; 0 on success

  // this is a fork point - NOT to be confused with the fork syscall
  if (pthread_create(&thread, NULL, thread_routine, (void *)thread_arg) != 0) {
    // error
    exit(1);
  }
}

// main function == main thread
int main(int argc, char const *argv[]) {
  thread_create();
  printf("blocked\n");
  pause();

  return 0;
}

// gcc threads_1.c -o main -lpthread