linux-C-信号量

deepfuture-lx@deepfuture-lx-desktop:~/private/mytest$ gcc -std=gnu99 -o testsem testsem.c

testsem.c: In function ‘get_sem_val’:

testsem.c:8: warning: implicit declaration of function ‘semctl’

testsem.c: In function ‘main’:

testsem.c:20: warning: implicit declaration of function ‘semget’

testsem.c:23: warning: implicit declaration of function ‘exit’

testsem.c:23: warning: incompatible implicit declaration of built-in function ‘exit’

testsem.c:31: warning: incompatible implicit declaration of built-in function ‘exit’

testsem.c:34: warning: implicit declaration of function ‘fork’

testsem.c:37: warning: incompatible implicit declaration of built-in function ‘exit’

testsem.c:44: warning: implicit declaration of function ‘semop’

testsem.c:58: warning: incompatible implicit declaration of built-in function ‘exit’

deepfuture-lx@deepfuture-lx-desktop:~/private/mytest$ ./testsem

create 65538 sem success!

0 生产者: 2

1 生产者: 3

2 生产者: 4

3 生产者: 5

4 生产者: 6

5 生产者: 7

6 生产者: 8

7 生产者: 9

8 生产者: 10

9 生产者: 11

10 生产者: 11

11 生产者: 12

12 生产者: 13

13 生产者: 14

14 生产者: 15

0 消费者: 11

1 消费者: 14

2 消费者: 13

3 消费者: 12

4 消费者: 11

5 消费者: 10

6 消费者: 9

7 消费者: 8

8 消费者: 7

9 消费者: 6

10 消费者: 5

11 消费者: 4

12 消费者: 3

13 消费者: 2

14 消费者: 1

deepfuture-lx@deepfuture-lx-desktop:~/private/mytest$ 

#include <stdio.h>
#include <linux/sem.h>
#define MAXNUMS 15


int get_sem_val(int sid,int semnum)//取得当前信号量
{
    return(semctl(sid,semnum,GETVAL,0));
}

int main(void){
    int sem_id;
    int pid;
    int rc;
    struct sembuf sem_op;//信号集结构
    union semun sem_val;//信号量数值
    
    
    //建立信号量集，其中只有一个信号量
    sem_id=semget(IPC_PRIVATE,1,IPC_CREAT|0600);//IPC_PRIVATE私有，只有本用户使用，如果为正整数，则为公共的；1为信号集的数量；
    if (sem_id==-1){
        printf("create sem error!\n");
        exit(1);    
    }
    printf("create %d sem success!\n",sem_id);    
    //信号量初始化
    sem_val.val=1;
    rc=semctl(sem_id,0,SETVAL,sem_val);//设置信号量,0为第一个信号量，1为第二个信号量,...以此类推；SETVAL表示设置
    if (rc==-1){
        printf("initlize sem error!\n");
        exit(1);    
    }
    //创建进程
    pid=fork();
    if (pid==-1){
        printf("fork error!\n");
        exit(1);           
    }
    else if(pid==0){//一个子进程，消费者
        for (int i=0;i<MAXNUMS;i++){
            sem_op.sem_num=0;
            sem_op.sem_op=-1;
            sem_op.sem_flg=0;
            semop(sem_id,&sem_op,1);//操作信号量，每次-1                
            printf("%d 消费者: %d\n",i,get_sem_val(sem_id,0));
        }     
    }
    else{//父进程，生产者
        for (int i=0;i<MAXNUMS;i++){
            sem_op.sem_num=0;
            sem_op.sem_op=1;
            sem_op.sem_flg=0;
            semop(sem_id,&sem_op,1);//操作信号量，每次+1                 
            printf("%d 生产者: %d\n",i,get_sem_val(sem_id,0));
            
        }     
    }
    exit(0);
}