线程的基本使用

线程
线程的绝大多数函数名都以pthread_开头，我们可以通过如下几步来线程函数库。
1：定义宏_REENTRANT；
2：在程序中包含头文件“pthread.h”；
3：在编译程序时需要用选项-lpthread来连接线程库；

步骤说明：
1：我们通过定义宏_REENTRANT来告诉编译器我们需要可重入功能。

2：头文件pthread.h中有我们需要的线程函数。
#include <pthread.h>

int pthread_create(pthread_t *thread, pthread_attr_t *attr, void*(*start_routine)(void*), void *arg);
void pthread_exit(void* retval);
int pthread_join(pthread_t th ,void **thread_return);
pthread_t pthread_self();

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

void *thread_function(void *arg);
int run_now = 1;
char message[] = "Hello World";

int main() {
int res;
pthread_t a_thread;
void *thread_result;
int print_count1 = 0;

res = pthread_create(&a_thread, NULL, thread_function, (void *)message);
if (res != 0) {
perror("Thread creation failed");
exit(EXIT_FAILURE);
}

pthread_t tid;
pid_t pid;
tid = pthread_self();
pid = getpid();
printf("thread_id and process_id is :[%lu]@[%lu]\n",tid,pid);

printf("\nWaiting for thread to finish...\n");
res = pthread_join(a_thread, &thread_result);
if (res != 0) {
perror("Thread join failed");
exit(EXIT_FAILURE);
}
printf("Thread joined\n");
exit(EXIT_SUCCESS);
}

void *thread_function(void *arg) {
pthread_t tid;
pid_t pid;
tid = pthread_self();
pid = getpid();
printf("thread_id and process_id is :[%lu]@[%lu]\n",tid,pid);

sleep(3);
}

编译上面的程序的命令是：
cc -D_REENTRANT -lpthread thread_test.c -o thread_test

信号量
信号量函数的名字都以sem_开头。

#include <semaphore.h>

int sem_init(sem_t *sem, int pshared, unsigned int value);
int sem_wait(sem_t *sem);
int sem_post(sem_t *sem);
int sem_destory(sem_t *sem);

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <semaphore.h>

void *thread_function(void *arg);
sem_t bin_sem;

#define WORK_SIZE 1024
char work_area[WORK_SIZE];

int main() {
int res;
pthread_t a_thread;
void *thread_result;

res = sem_init(&bin_sem, 0, 0);
if (res != 0) {
perror("Semaphore initialization failed");
exit(EXIT_FAILURE);
}
res = pthread_create(&a_thread, NULL, thread_function, NULL);
if (res != 0) {
perror("Thread creation failed");
exit(EXIT_FAILURE);
}
printf("Input some text. Enter 'end' to finish\n");
while(strncmp("end", work_area, 3) != 0) {
fgets(work_area, WORK_SIZE, stdin);
sem_post(&bin_sem);
}
printf("\nWaiting for thread to finish...\n");
res = pthread_join(a_thread, &thread_result);
if (res != 0) {
perror("Thread join failed");
exit(EXIT_FAILURE);
}
printf("Thread joined\n");
sem_destroy(&bin_sem);
exit(EXIT_SUCCESS);
}

void *thread_function(void *arg) {
sem_wait(&bin_sem);
while(strncmp("end", work_area, 3) != 0) {
printf("You input %d characters\n", strlen(work_area) -1);
sem_wait(&bin_sem);
}
pthread_exit(NULL);
}

互斥量

#include <pthread.h>

int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutexattr);
int pthread_mutex_lock(pthread_mutex_t *mutex);
int pthread_mutex_unlock(pthread_mutex_t *mutex);
int pthread_mutex_destroy(pthread_mutex_t *mutex);

举例：
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <semaphore.h>

void *thread_function(void *arg);
pthread_mutex_t work_mutex; /* protects both work_area and time_to_exit */

#define WORK_SIZE 1024
char work_area[WORK_SIZE];
int time_to_exit = 0;

int main() {
int res;
pthread_t a_thread;
void *thread_result;
res = pthread_mutex_init(&work_mutex, NULL);
if (res != 0) {
perror("Mutex initialization failed");
exit(EXIT_FAILURE);
}
res = pthread_create(&a_thread, NULL, thread_function, NULL);
if (res != 0) {
perror("Thread creation failed");
exit(EXIT_FAILURE);
}
pthread_mutex_lock(&work_mutex);
printf("Input some text. Enter 'end' to finish\n");
while(!time_to_exit) {
fgets(work_area, WORK_SIZE, stdin);
pthread_mutex_unlock(&work_mutex);
while(1) {
pthread_mutex_lock(&work_mutex);
if (work_area[0] != '\0') {
pthread_mutex_unlock(&work_mutex);
sleep(1);
}
else {
break;
}
}
}
pthread_mutex_unlock(&work_mutex);
printf("\nWaiting for thread to finish...\n");
res = pthread_join(a_thread, &thread_result);
if (res != 0) {
perror("Thread join failed");
exit(EXIT_FAILURE);
}
printf("Thread joined\n");
pthread_mutex_destroy(&work_mutex);
exit(EXIT_SUCCESS);
}

void *thread_function(void *arg) {
sleep(1);
pthread_mutex_lock(&work_mutex);
while(strncmp("end", work_area, 3) != 0) {
printf("You input %d characters\n", strlen(work_area) -1);
work_area[0] = '\0';
pthread_mutex_unlock(&work_mutex);
sleep(1);
pthread_mutex_lock(&work_mutex);
while (work_area[0] == '\0' ) {
pthread_mutex_unlock(&work_mutex);
sleep(1);
pthread_mutex_lock(&work_mutex);
}
}
time_to_exit = 1;
work_area[0] = '\0';
pthread_mutex_unlock(&work_mutex);
pthread_exit(0);
}

线程的属性

#include <pthread.h>
int pthread_attr_init(pthread_attr_t *attr);
int pthread_attr_destroy(pthread_attr_t *attr);

分离线程
分离线程之后，新线程已经脱离原线程，不再能用pthread_join ()进行合并。
#include <pthread.h>

int pthread_detach(pthread_t thread);

取消线程
#include <pthread.h>

int pthread_cancel(pthread_t thread);