linux 信号量编写

本次主要写了两个程序，一个用于对信号量进行p操作，一个用于进行v操作。p操作导致资源阻塞时，必须等待v操作释放资源。

p操作代码如下:

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <string.h>
#include <signal.h>

int semId;
int SIZE = 1;

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) */
};

void Handle(int s){
  if(s == 2){
    semctl(semId,0,IPC_RMID);
    exit(0);
  }
}


int main(){
  signal(2,Handle);

  key_t key = ftok(".",4);
  semId = semget(key,1,IPC_CREAT | IPC_EXCL | 0666);
  
  union semun v;
  v.val = SIZE;

  if(semctl(semId,0,SETVAL,v) == -1){
    printf("semctl error!\n"); 
    exit(0);
  }


  struct sembuf sop;
  sop.sem_num = 0;
  sop.sem_op = -1;
  sop.sem_flg = 0;


  while(1){
    semop(semId,&sop,1);
    printf("go go go!!!\n");
    sleep(1);

  }

  return 0;
}

v操作代码如下:

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <string.h>
#include <signal.h>

int semId;

int main(){

  key_t key = ftok(".",4);
  semId = semget(key,0,0);
  

  struct sembuf sop;
  sop.sem_num = 0;
  sop.sem_op = 1;
  sop.sem_flg = 0;


  while(1){
    if(semop(semId,&sop,1) == -1) exit(0);
    sleep(1);
  }

  return 0;
}

运行结果如下：