Question

Please finish the following program

/**
	* Basic POSIX Thread (pthread) Usage 1.
	*
	* By walking through this example you’ll learn:
	* - How to use pthread_create().
	* - How to use pthread_exit().
	* - How to use pthread_join().
	*
	*/
	#include <stdio.h>
	#include <unistd.h>
	#include <pthread.h>
	#include <sys/wait.h>
	void* ninja(void* arg){
	printf("Who’s there?");
	fflush(stdout);
	pthread_exit("ninja");
	}
	//
	// Expected output:
	//
	// Knock knock.
	// Who's there? - from ninja
	// Knuc...kles.
	//
	int main(int argc, char* argv[]){
	pthread_t tid;
	char* from = "";
	printf("Knock knock.\n");
	// HINT: The thread that runs `ninja` should be created.
	int status = pthread_<?1/>(<?2/>);
	if(status != 0){
	printf("WTF?");
	return -1;
	}
	// HINT: The main thread should not be exited until `ninja` has finished.
	pthread_<?3/>(<?4/>);
	// HINT: The variable `from` should not be empty.
	printf(" - from %s\n", from);
	printf("Knuc...kles.\n");
	return 0;
	}

Answer 1

#include <stdio.h>
   #include <unistd.h>
   #include <pthread.h>
   #include <sys/wait.h>
  
   void* ninja(void* arg){
   printf("Who’s there?");
   fflush(stdout);
  
   pthread_exit("ninja");
   }
  
  
  
   //
   // Expected output:
   //
   // Knock knock.
   // Who's there? - from ninja
   // Knuc...kles.
   //
  
   int main(int argc, char* argv[]){
   pthread_t tid;
   char* from = "";
  
   printf("Knock knock.\n");
  
   // HINT: The thread that runs `ninja` should be created.
   int status = pthread_create(&tid, NULL, &ninja, NULL);
  
   if(status != 0){
   printf("WTF?");
   return -1;
   }
  
   // HINT: The main thread should not be exited until `ninja` has finished.
   pthread_join(tid,NULL);
  
   // HINT: The variable `from` should not be empty.
   printf(" - from %s\n", from);
  
   printf("Knuc...kles.\n");
  
   return 0;
   }

Ouput: