信号量的创建和删除

1. 创建信号量，并利用ipcs -s查看信号量：

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

int main(void)
{
    int semid;
    int nsems = 1;//semaphores nums to create
    int flags = 0666;   //world read-alter mode
    struct sembuf buf;  //how semop should behave

    //create the semaphore with world read-alter perms
    semid = semget(IPC_PRIVATE, nsems, flags);
    if(semid < 0)
    {
        perror("semget");
        exit(EXIT_FAILURE);
    }
    printf("semaphore created: %d\n", semid);

    //set up the structure for semop
    buf.sem_num = 0;    //A single semaphore
    buf.sem_flg = IPC_NOWAIT;  //don't block

    if((semop(semid, &buf, nsems)) < 0)
    {
        perror("semop");
        exit(EXIT_FAILURE);
    }

    system("ipcs -s");
    exit(EXIT_SUCCESS);
}

2. 清除信号量，并利用ipcs -s查看信号量：

//Manipulate and delete a semaphore

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

int main(int argc, char *argv[])
{
	int semid;
	if(argc != 2)
	{
		puts("USAGE:stl1 <semaphore if>");
		exit(EXIT_FAILURE);
	}
	semid = atoi(argv[1]);

	//remove the semaphore
	if((semctl(semid, 0, IPC_RMID))<0)
	{
		perror("semctl IPC_RMID");
		exit(EXIT_FAILURE);
	}
	else
	{
		puts("semaphore removed");
		system("ipcs -s");
	}
	exit(EXIT_SUCCESS);
}

来源：CSDN

作者：5C_King

链接：https://blog.csdn.net/u013639526/article/details/23389597

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