Pthreads（POSIX Threads）參考 POSIX 標準定義執行緒產生和同步的API，是執行緒行為規格，而非製作。主要在Unix和類Unix系統（如Linux和macOS）中使用。它提供了一組函數來創建和管理線程，使得開發者可以在應用程式中實現並行處理。

thrd-posix.c

/**
 * A pthread program illustrating how to
 * create a simple thread and some of the pthread API
 * This program implements the summation function where
 * the summation operation is run as a separate thread.
 *
 * Most Unix/Linux/OS X users
 * gcc thrd.c -lpthread
 *
 * Solaris users must enter
 * gcc thrd.c -lpthreads
 *
 * Figure 4.9
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts  - Ninth Edition
 * Copyright John Wiley & Sons - 2013
 */

#include <pthread.h>
#include <stdio.h>

int sum; /* this data is shared by the thread(s) */

void *runner(void *param); /* the thread */

int main(int argc, char *argv[]) /* 當程式啟動時，OS創建並執行主線程，並進入 main 函數 */
{
pthread_t tid; /* the thread identifier */
pthread_attr_t attr; /* set of attributes for the thread */

if (argc != 2) {
	fprintf(stderr,"usage: a.out <integer value>\n");
	/*exit(1);*/
	return -1;
}

/* 命令行參數檢查 */
if (atoi(argv[1]) < 0) {
	fprintf(stderr,"Argument %d must be non-negative\n",atoi(argv[1]));
	/*exit(1);*/
	return -1;
}

/* get the default attributes 初始化線程屬性 */
pthread_attr_init(&attr);

/* create the thread 創建子線程 */
pthread_create(&tid,&attr,runner,argv[1]);

/* now wait for the thread to exit 等待子線程結束 */
pthread_join(tid,NULL);

printf("sum = %d\n",sum);
}

/**
 * The thread will begin control in this function
 */
void *runner(void *param) 
{
int i, upper = atoi(param);
sum = 0;

	if (upper > 0) {
		for (i = 1; i <= upper; i++)
			sum += i;
	}

	pthread_exit(0);
}

Terminal
編譯並執行

gcc thrd-posix.c -lpthread
./a.out 10

結果：

參考：greggagne/OSC9e/ch4/thrd-posix.c
More：並行程式設計: 概念