linux通信--信号量

来源：互联网发布：sql语句编辑：程序博客网时间：2024/06/14 03:48
程序主要参考：http://hector.blog.51cto.com/4229131/758930
#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/sem.h> #include <sys/stat.h> #include <fcntl.h>  union semun //必须自己定义{     int val;     struct semid_ds *buf;     unsigned short int *array;     struct seminfo *__buf; }; void p(int k){ sb.sem_num = k; //将k号信号量   sb.sem_op = -1; //减1   sb.sem_flg = SEM_UNDO;    semop(semid, &sb, 1); //原子p操作，   //semop(int semid,struct sembuf semoparray[],size_t nops)对信号量集合semid进行p操作，操作的内容在semoparray,nops表明前面数组的大小}void v(int k){sb.sem_num = k; //将k号信号量  sb.sem_op = 1;  //加1  sb.sem_flg = SEM_UNDO;   semop(semid, &sb, 1); //操作信号量} int main(void) {     char* buf_child[]={"this", "is", "the", "child", "process"};     char* buf_father[]={"father", "say", "hello", "to", "child"};     int i = 0, semid, fd;     pid_t pid;     struct sembuf sb; //信号量操作    union semun sem;     semid = semget(1000, 2, 0666 | IPC_CREAT); //申请信号量组，包含2个信号量     sem.val = 0;     //semctl(int semid,int semnum,int cmd,union semun)对信号量集合中的第semnum号信号进行cmd操作，操作的具体数值放在semun中    semctl(semid, 0, SETVAL, sem); //初始化0号信号量为0    sem.val = 1;     semctl(semid, 1, SETVAL, sem); //初始化1号信号量为1     fd=open("tmp",O_CREAT|O_TRUNC|O_WRONLY,0666);      pid = fork();     switch (pid) {         case -1:             perror("fork fail");             break;         case 0: /* child consume */             srand((unsigned int)getpid());             while (i < 5) {                                p(1);//child 只看1号信号量                write(fd,buf_child[i], strlen(buf_child[i]));                 sleep(rand());                 write(fd,&" ", 1);                 i++;                 v(0);                            }             break;         default:/* parent production  */             srand((unsigned int)getpid());             while (i < 5) {                 p(0);//parent 只看0号信号量                 write(fd,buf_father[i], strlen(buf_father[i]));                 sleep(rand());                 write(fd,&" ", 1);                 i++;                  v(1);            }             break;     }     return 0; }