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  • linux c编程 多线程（初级）《转载》---赠人玫瑰，手有余香！

     

    原文地址：http://blog.csdn.net/liang890319/article/details/8393120

     

    进程简单的说就是把一段代码复制成多份，并让他们同时执行。进程间通信是为了让他们有序的运行

    线程简单的说就是让多个函数同时执行，线程间通信是为了让他们有序的运行

    编译线程程序时会警告说线程函数找不到

     pthread 库不是 Linux 系统默认的库，连接时需要使用静态库 libpthread.a，所以在使用pthread_create()创建线程，以及调用 pthread_atfork()函数建立fork处理程序时，需要链接该库。

    问题解决：
        在编译中要加 -lpthread参数
        gcc thread.c -o thread -lpthread
        thread.c为你些的源文件，不要忘了加上头文件#include<pthread.h>

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

    实例1：创建两个线程，同时执行同一个函数

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


    void print_msg(char *ptr);


    int main()
    {
    pthread_t thread1, thread2;
    int i,j;
    char *msg1="do sth1 ";
    char *msg2="do sth2 ";
    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 ",id);
      printf("%s",ptr);
    pthread_exit(&retval);
    }

    执行gcc ex7-1.c -lpthread

    ./a.out

    实例2  创建多个线程执行不同函数

    代码来自 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 ");
        for (i = 0; i < MAX; i++)
            {
                printf("thread1 : number = %d ",number);
                pthread_mutex_lock(&mut);
                number++;
                pthread_mutex_unlock(&mut);
                sleep(2);
            }
        printf("thread1 :主函数在等我完成任务吗？ ");
     
        pthread_exit(NULL);
     
    }
     
    void *thread2()
    {
        printf("thread2 : I'm thread 2 ");
        for (i = 0; i < MAX; i++)
            {
                printf("thread2 : number = %d ",number);
                pthread_mutex_lock(&mut);
                number++;
                pthread_mutex_unlock(&mut);
                sleep(3);
            }
        printf("thread2 :主函数在等我完成任务吗？ ");
        pthread_exit(NULL);
    }
     
     
    void thread_create(void)
    {
        int temp;
        memset(&thread, 0, sizeof(thread)); //comment1
        //创建线程
        if((temp = pthread_create(&thread[0], NULL, thread1, NULL)) != 0) //comment2
            printf("线程1创建失败! ");
        else
            printf("线程1被创建 ");
        if((temp = pthread_create(&thread[1], NULL, thread2, NULL)) != 0) //comment3
            printf("线程2创建失败");
        else
            printf("线程2被创建 ");
    }
     
    void thread_wait(void)
    {
        //等待线程结束
        if(thread[0] !=0) { //comment4
            pthread_join(thread[0],NULL);
            printf("线程1已经结束 ");
        }
        if(thread[1] !=0) { //comment5
            pthread_join(thread[1],NULL);
            printf("线程2已经结束 ");
        }
    }
     
    int main()
    {
        //用默认属性初始化互斥锁
        pthread_mutex_init(&mut,NULL);
        printf("我是主函数哦，我正在创建线程，呵呵 ");
        thread_create();
        printf("我是主函数哦，我正在等待线程完成任务阿，呵呵 ");
        thread_wait();
        return 0;
    }


    ?

    编译 :

           gcc -lpthread -o thread_example lp.c


    实例3：信号量控制线程运行顺序



    /* 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 ", thrd_num);

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

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


    printf("Thread %d finished ", 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 ", no);
    exit(res);
    }
    }

    printf("Create treads success Waiting for threads to finish... ");
    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 ", no);
    }
    else
    {
    printf("Thread %d join failed ", no);
    }
    sem_post(&sem[(no + THREAD_NUMBER - 1) % THREAD_NUMBER]);

    }

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


    return 0;        
    }

    实例4：互斥锁的使用

    在这个程序中，一个线程要往缓冲区写数据，另一个线程要读数据，每次只能让一个线程操作缓冲区

    /*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 ",i++);
    buffer_has_item=1;
    }
    pthread_mutex_unlock(&mutex);
    }
    }

    实例5 条件变量

    text

    [cpp] view plaincopyprint?
     
    1. /* ex7-4.c */  
    2. #include <stdio.h>  
    3. #include <pthread.h>  
    4. #define BUFFER_SIZE 4  
    5. #define OVER (-1)  
    6. struct producers  
    7. {  
    8.     int buffer[BUFFER_SIZE];  
    9.     pthread_mutex_t lock;  
    10.     int     readpos, writepos;  
    11.     pthread_cond_t  notempty;  
    12.     pthread_cond_t  notfull;  
    13. };  
    14.   
    15. void init(struct producers *b)  
    16. {  
    17.     pthread_mutex_init(&b->lock,NULL);  
    18.     pthread_cond_init(&b->notempty,NULL);  
    19.     pthread_cond_init(&b->notfull,NULL);  
    20.     b->readpos=0;  
    21.     b->writepos=0;  
    22. }  
    23.   
    24. void put(struct producers *b, int data)  
    25. {  
    26.     pthread_mutex_lock(&b->lock);  
    27.     while((b->writepos+1)%BUFFER_SIZE==b->readpos)  
    28.     {  
    29.         pthread_cond_wait(&b->notfull,&b->lock);  
    30.     }  
    31.   
    32.     b->buffer[b->writepos]=data;  
    33.     b->writepos++;  
    34.     if(b->writepos>=BUFFER_SIZE) b->writepos=0;  
    35.     pthread_cond_signal(&b->notempty);  
    36.     pthread_mutex_unlock(&b->lock);  
    37. }  
    38.   
    39. int get(struct producers *b)  
    40. {  
    41.     int data;  
    42.     pthread_mutex_lock(&b->lock);  
    43.     while(b->writepos==b->readpos)  
    44.     {  
    45.         pthread_cond_wait(&b->notempty,&b->lock);  
    46.     }  
    47.     data=b->buffer[b->readpos];  
    48.     b->readpos++;  
    49.     if(b->readpos>=BUFFER_SIZE) b->readpos=0;  
    50.     pthread_cond_signal(&b->notfull);  
    51.     pthread_mutex_unlock(&b->lock);  
    52.     return data;  
    53. }  
    54.   
    55. struct producers  buffer;  
    56. void *producer(void *data)  
    57. {  
    58.     int n;  
    59.     for(n=0;n<10;n++)  
    60.     {  
    61.         printf("Producer : %d--> ",n);  
    62.         put(&buffer,n);  
    63.     }  
    64.     put(&buffer,OVER);  
    65.     return NULL;  
    66. }  
    67.   
    68. void *consumer(void *data)  
    69. {  
    70.     int d;  
    71.     while(1)  
    72.     {  
    73.         d=get(&buffer);  
    74.         if(d==OVER) break;  
    75.         printf("Consumer: --> %d ",d);  
    76.     }  
    77.     return NULL;  
    78. }  
    79.   
    80. int main()  
    81. {  
    82.     pthread_t tha,thb;  
    83.     void *retval;  
    84.     init(&buffer);  
    85.     pthread_create(&tha,NULL,producer,0);  
    86.     pthread_create(&thb,NULL,consumer,0);  
    87.     pthread_join(tha,&retval);  
    88.     pthread_join(thb,&retval);  
    89.     return 0;  
    90.   
    91. }  
    一分耕耘，一分收获！
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  • 原文地址：https://www.cnblogs.com/splovecyk/p/4382012.html
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