linux c編程多線程（初級）

時間 2019-12-05

原文原文鏈接

進程簡單的說就是把一段代碼複製成多份，並讓他們同時執行。進程間通訊是爲了讓他們有序的運行html

線程簡單的說就是讓多個函數同時執行，線程間通訊是爲了讓他們有序的運行app

編譯線程程序時會警告說線程函數找不到函數

pthread 庫不是 Linux 系統默認的庫，鏈接時須要使用靜態庫 libpthread.a，因此在使用pthread_create()建立線程，以及調用 pthread_atfork()函數創建fork處理程序時，須要連接該庫。

問題解決：
    在編譯中要加 -lpthread參數
    gcc thread.c -o thread -lpthread
    thread.c爲你些的源文件，不要忘了加上頭文件#include<pthread.h>post

http://blog.csdn.net/llqkk/article/details/2854558spa

實例1：建立兩個線程，同時執行同一個函數.net

/* ex7-1.c */
#include <stddef.h>
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>線程

void print_msg(char *ptr);htm

int main()
{
pthread_t thread1, thread2;
int i,j;
char *msg1="do sth1\n";
char *msg2="do sth2\n";
pthread_create(&thread1,NULL, (void *)(&print_msg), (void *)msg1);
pthread_create(&thread2,NULL, (void *)(&print_msg), (void *)msg2);
sleep(1);
return 0;
}

void print_msg(char *ptr)
{
int retval;
int id=pthread_self();
printf("Thread ID: %x\n",id);
printf("%s",ptr);
pthread_exit(&retval);
}blog

執行gcc ex7-1.c -lpthread進程

./a.out

實例2 建立多個線程執行不一樣函數

代碼來自 http://www.cnblogs.com/BiffoLee/archive/2011/11/18/2254540.html

#include <pthread.h>
#include <stdio.h>
#include <sys/time.h>
#include <string.h>
#define MAX 10

pthread_t thread[2];
pthread_mutex_t mut;
int number=0, i;

void *thread1()
{
printf ("thread1 : I'm thread 1\n");
for (i = 0; i < MAX; i++)
{
printf("thread1 : number = %d\n",number);
pthread_mutex_lock(&mut);
number++;
pthread_mutex_unlock(&mut);
sleep(2);
}
printf("thread1 :主函數在等我完成任務嗎？\n");

pthread_exit(NULL);

}

void *thread2()
{
printf("thread2 : I'm thread 2\n");
for (i = 0; i < MAX; i++)
{
printf("thread2 : number = %d\n",number);
pthread_mutex_lock(&mut);
number++;
pthread_mutex_unlock(&mut);
sleep(3);
}
printf("thread2 :主函數在等我完成任務嗎？\n");
pthread_exit(NULL);
}

void thread_create(void)
{
int temp;
memset(&thread, 0, sizeof(thread)); //comment1
//建立線程
if((temp = pthread_create(&thread[0], NULL, thread1, NULL)) != 0) //comment2
printf("線程1建立失敗!\n");
else
printf("線程1被建立\n");
if((temp = pthread_create(&thread[1], NULL, thread2, NULL)) != 0) //comment3
printf("線程2建立失敗");
else
printf("線程2被建立\n");
}

void thread_wait(void)
{
//等待線程結束
if(thread[0] !=0) { //comment4
pthread_join(thread[0],NULL);
printf("線程1已經結束\n");
}
if(thread[1] !=0) { //comment5
pthread_join(thread[1],NULL);
printf("線程2已經結束\n");
}
}

int main()
{
//用默認屬性初始化互斥鎖
pthread_mutex_init(&mut,NULL);
printf("我是主函數哦，我正在建立線程，呵呵\n");
thread_create();
printf("我是主函數哦，我正在等待線程完成任務阿，呵呵\n");
thread_wait();
return 0;
}

編譯 :

gcc -lpthread -o thread_example lp.c

實例3：信號量控制線程運行順序

/* thread_sem.c */

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

#define THREAD_NUMBER 3
#define REPEAT_NUMBER 3
#define DELAY_TIME_LEVELS 10.0

sem_t sem[THREAD_NUMBER];

void * thrd_func(void *arg)
{
int thrd_num = (int)arg;
int delay_time = 0;
int count = 0;

sem_wait(&sem[thrd_num]);

printf("Thread %d is starting\n", thrd_num);

for (count = 0; count < REPEAT_NUMBER; count++)
{

delay_time = (int)(rand() * DELAY_TIME_LEVELS/(RAND_MAX)) + 1;
sleep(delay_time);
printf("\tThread %d: job %d delay = %d\n", thrd_num, count, delay_time);
}

printf("Thread %d finished\n", thrd_num);

pthread_exit(NULL);
}

int main(void)
{
pthread_t thread[THREAD_NUMBER];
int no = 0, res;
void * thrd_ret;

srand(time(NULL));

for (no = 0; no < THREAD_NUMBER; no++)
{
sem_init(&sem[no], 0, 0);
res = pthread_create(&thread[no], NULL, thrd_func, (void*)no);
if (res != 0)
{
printf("Create thread %d failed\n", no);
exit(res);
}
}

printf("Create treads success\n Waiting for threads to finish...\n");
sem_post(&sem[THREAD_NUMBER - 1]);
for (no = THREAD_NUMBER - 1; no >= 0; no--)
{
res = pthread_join(thread[no], &thrd_ret);
if (!res)
{
printf("Thread %d joined\n", no);
}
else
{
printf("Thread %d join failed\n", no);
}
sem_post(&sem[(no + THREAD_NUMBER - 1) % THREAD_NUMBER]);

}

for (no = 0; no < THREAD_NUMBER; no++)
{
sem_destroy(&sem[no]);
}

return 0;
}

實例4：互斥鎖的使用

在這個程序中，一個線程要往緩衝區寫數據，另外一個線程要讀數據，每次只能讓一個線程操做緩衝區

/*ex7-3.c*/

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

#define FALSE 0
#define TRUE 1

void readfun();
void writefun();

char buffer[256];
int buffer_has_item=0;
int retflag=FALSE,i=0;
pthread_mutex_t mutex;

int main()
{
void *retval;
pthread_t reader;
pthread_mutex_init(&mutex,NULL);
pthread_create(&reader,NULL,(void *)&readfun,NULL);
writefun();
pthread_join(reader,&retval);

}

void readfun()
{
while(1)
{
if(retflag)
return;
pthread_mutex_lock(&mutex);
if(buffer_has_item==1)
{
printf("%s",buffer);
buffer_has_item=0;
}
pthread_mutex_unlock(&mutex);
}
}
void writefun()
{
int i=0;
while(1)
{
if(i==10)
{
retflag=TRUE;
return;
}
pthread_mutex_lock(&mutex);
if(buffer_has_item==0)
{
sprintf(buffer,"This is %d\n",i++);
buffer_has_item=1;
}
pthread_mutex_unlock(&mutex);
}
}