POSIX Thread

The most common thread package on Unix systems.

Process

1. Thread is created with pthread_create() to run a function, or to continue main
2. Thread terminates by returning from the given function or from main or from calling pthread_exit() 3. pthread_join() used to reap the return value from thread

Functions

• pthread_create()
• pthread_join()
• pthread_exit()
• pthread_detach()
• pthread_self()
• pthread_mutex_init()
• pthread_mutex_lock()
• pthread_mutex_trylock()
• pthread_mutex_unlock()
• pthread_mutex_destroy()

Examples

Simple Fn Call Example

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <pthread.h>
 
typedef struct myArg {
	int fd;
	char name[25];
} MyArg;
 
void* myThreadLength(void *p){
	MyArg *theArg = (MyArg*)p;
	int* length = (int*)malloc(sizeof(int));
	*length = strlen(theArg->name);
	return length;
}
 
int main(){
	int fd = open("afile", O_RDWR);
	MyArg* p = (MyArg*)malloc(sizeof(MyArg));
	p->fd = fd;
	strncpy(p->name, "daniel", 7);
  p->name[6]='\0';
 
	pthread_t thread_ID;
	void* status;
	int err = pthread_create(&thread_ID, NULL, myThreadLength, (void*)p);
	if (err != 0) {
		printf("%s", strerror(err));
	}
  pthread_join(thread_ID, &status);
  printf("%d", *(int*)status);
 
  close(fd);
  return 0;
}

Mutex Example

pthread_mutex_t myMutex;
int status;
 
status = pthread_mutex_init(&myMutex, NULL);
if (status != 0) printf("%s", strerror(status));
pthread_mutex_lock(&myMutex);
// critical section here
pthread_mutex_unlock(&myMutex);
 
status = pthread_mutex_destroy(&myMutex);
if (status != 0) printf("%s", strerror(status));