查看信号量对象的命令是

ipcs -s

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

#define SEMID 1234

union semun {
    int val;
    struct semid_ds *buf;
    unsigned short *array;
};

int main() {
    key_t key = ftok("/tmp", 'S');
    int semid = semget(key, 1, IPC_CREAT | 0666);
    if (semid == -1) {
        perror("semget");
        exit(EXIT_FAILURE);
    }

    union semun arg;
    arg.val = 1; // 初始值为1
    if (semctl(semid, 0, SETVAL, arg) == -1) {
        perror("semctl");
        exit(EXIT_FAILURE);
    }

    struct sembuf sb = {0, -1, SEM_UNDO}; // 获取信号量
    if (semop(semid, &sb, 1) == -1) {
        perror("semop");
        exit(EXIT_FAILURE);
    }

    printf("Semaphore acquired\n");

    sb.sem_op = 1; // 释放信号量
    if (semop(semid, &sb, 1) == -1) {
        perror("semop");
        exit(EXIT_FAILURE);
    }

    printf("Semaphore released\n");

    if (semctl(semid, 0, IPC_RMID) == -1) {
        perror("semctl");
        exit(EXIT_FAILURE);
    }

    return 0;
}