通信方式--信号量的一系列操作（创建 获取 设置 删除以及PV操作）

//....................#include"utili.h"#include<stdio.h>#include<unistd.h>#include<sys/ipc.h>#include<sys/sem.h>#include<stdlib.h>//.....................sem_create mysem.c#include"utili.h"int main(int argc,char *argv[]){    key_t sem_key = ftok(argv[1],0xff);    if(sem_key == -1)    {        perror("ftok");        exit(1);    }  /*semget(key_t key,int nsems,int oflag)           关键字    信号量个数  设置信号量的访问权限标志 关于oflag参数：1.IPC_CTEAT  即如果所指定键的IPC对象不存在，就创建一个新对象 否则返回该对象                2.同时设置oflag的IPC——CREAT和IPC——EXCL位时，即如果所指定键的IPC对象不存在，就创建一个新的对象，否则返回一个EEXIST错误，因为该对象已存在*/    int sem_id = semget(sem_key,1,IPC_CREAT|IPC_EXCL|0755);    if(sem_id == -1)    {        perror("semget");        exit(1);    }    printf("create sem ok.\n");   return 0;}//...................................sem_get.c#include"utili.h"int main(int argc,char *argv[]){   key_t sem_key = ftok(argv[1],0xff);   int sem_id = semget(sem_key,0,0);//创建信号量   int val = semctl(sem_id,0,GETVAL); //semctl控制函数   printf("sem_val = %d\n",val); //val= 0 没有资源 阻塞    return 0;}// ........................................ set_sem.c#include"utili.h" union semun {        int              val;    /* Value for SETVAL */        struct semid_ds *buf;    /* Buffer for IPC_STAT, IPC_SET */        unsigned short  *array;  /* Array for GETALL, SETALL*/         struct seminfo  *__buf;  /* Buffer for IPC_INFO                                           (Linux-specific) */};//设置信号量int main(int argc,char *argv[]){       key_t sem_key = ftok(argv[1],0xff);       int sem_id = semget(sem_key,0,0);       union semun val;       val.val =atoi(argv[2]); //atoi 将字符串转换为整型数       semctl(sem_id,0,SETVAL,val);     return 0;}//.............................sem_p.c#include"utili.h"int main(int argc,char *argv[]){  key_t sem_key = ftok(argv[1],0xff);  int sem_id = semget(sem_key,0,0);  struct sembuf op;  op.sem_num = 0;  op.sem_op = -1; // op.sem_flg = 0;  op.sem_flg = SEM_UNDO;  semop(sem_id,&op,1);  return 0;}sem_v.c#include"utili.h"/* 信号量的值仅能由pv操作来改变PV操作通过调用函数semop来实现int semop(int semid,struct sembuf *sops ,size_t nsops);           标示符 sops指向结构体数组的首地址 信号的个数struct sembuf{  ushort  sem_num;  //信号在信号集中的索引  short   sem_op; //操作类型  short   sem_flg; //操作标志}*/int main(int argc,char *argv[]){    key_t sem_key = ftok(argv[1],0xff);    int sem_id = semget(sem_key,0,0);    struct sembuf op;    op.sem_num = 0;    op.sem_op =1;    op.sem_flg = 0;    semop(sem_id,&op,1);    return 0;}//........................sem_remove.c#include"utili.h"int main(int argc,char *argv[]){    key_t  sem_key = ftok(argv[1],0xff);    int sem_id = semget(sem_key,0,0);    int res = semctl(sem_id,0,IPC_RMID);    if(res == -1)    {        printf("remove sem Erroe.\n");    }    else        printf("remove sem Ok.\n");    return 0;}