linuxIPC之信号量(集)

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吐舌头示例

/*************************************************************************> File Name: sema.c> Author: XXDK> Email: v.manstein@qq.com > Created Time: Mon 20 Mar 2017 04:22:33 PM CST ************************************************************************/#include<stdio.h>#include<stdlib.h>#include<unistd.h>#include<errno.h>#include<sys/ipc.h>#include<sys/sem.h>#include<sys/types.h>#include<fcntl.h>union semnu {int val;};int main(int argc, const char* argv[]){int semid;key_t key;union semnu sema, semb;key = ftok("./.", 100);semid = semget(key, 2, IPC_CREAT|IPC_EXCL|0666);if(semid == -1) {if(errno == EEXIST) {semid = semget(key, 2, 0666);} else {perror("fail to semget");}} else {sema.val =20;semctl(semid, 0, SETVAL, sema);semb.val = 50;semctl(semid, 1, SETVAL, semb);}struct sembuf sbufa, sbufb;sbufa.sem_num = 0;sbufa.sem_op = -5;sbufa.sem_flg = 0;semop(semid, &sbufa, 1);sbufb.sem_num = 0;sbufb.sem_op = -5;sbufb.sem_flg = 0;semop(semid, &sbufb, 1);printf("smea: %d\n", semctl(semid, 0, GETVAL));printf("smea: %d\n", semctl(semid, 1, GETVAL));return 0;}

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