Linux進程間的五種通信方式介紹 6

client.c

#include#include // shared memory#include // semaphore#include // message queue
// 消息隊列結構struct msg_form {    long mtype;    char mtext;};
// 聯合體，用于semctl初始化union semun{    int              val; /for SETVAL/    struct semid_ds buf;    unsigned short  *array;};
// P操作://  若信號量值為1，獲取資源并將信號量值-1 //  若信號量值為0，進程掛起等待int sem_p(int sem_id){    struct sembuf sbuf;    sbuf.sem_num = 0; /序號/    sbuf.sem_op = -1; /P操作/    sbuf.sem_flg = SEM_UNDO;
    if(semop(sem_id, &sbuf, 1) == -1)    {        perror("P operation Error");        return -1;    }    return 0;}
// V操作：//  釋放資源并將信號量值+1//  如果有進程正在掛起等待，則喚醒它們int sem_v(int sem_id){    struct sembuf sbuf;    sbuf.sem_num = 0; /序號/    sbuf.sem_op = 1;  /V操作/    sbuf.sem_flg = SEM_UNDO;
    if(semop(sem_id, &sbuf, 1) == -1)    {        perror("V operation Error");        return -1;    }    return 0;}
int main(){    key_t key;    int shmid, semid, msqid;    char shm;    struct msg_form msg;    int flag = 1; /while循環條件/
    // 獲取key值    if((key = ftok(".", 'z')) < 0)    {        perror("ftok error");        exit(1);    }
    // 獲取共享內存    if((shmid = shmget(key, 1024, 0)) == -1)    {        perror("shmget error");        exit(1);    }
    // 連接共享內存    shm = (char*)shmat(shmid, 0, 0);    if((int)shm == -1)    {        perror("Attach Shared Memory Error");        exit(1);    }
    // 創建消息隊列    if ((msqid = msgget(key, 0)) == -1)    {        perror("msgget error");        exit(1);    }
    // 獲取信號量    if((semid = semget(key, 0, 0)) == -1)    {        perror("semget error");        exit(1);    }    // 寫數據    printf("\\n");    printf("*                 IPC                 \\n");    printf("    Input r to send data to server.  \\n");    printf("    Input q to quit.                 \\n");    printf("\\n");    while(flag)    {        char c;        printf("Please input command: ");        scanf("%c", &c);        switch(c)        {            case 'r':                printf("Data to send: ");                sem_p(semid);  /訪問資源/                scanf("%s", shm);                sem_v(semid);  /釋放資源/                /清空標準輸入緩沖區/                while((c=getchar())!='\\n' && c!=EOF);                msg.mtype = 888;                  msg.mtext = 'r';  /發送消息通知服務器讀數據/                msgsnd(msqid, &msg, sizeof(msg.mtext), 0);                break;            case 'q':                msg.mtype = 888;                msg.mtext = 'q';                msgsnd(msqid, &msg, sizeof(msg.mtext), 0);                flag = 0;                break;            default:                printf("Wrong input!\\n");                /清空標準輸入緩沖區*/                while((c=getchar())!='\\n' && c!=EOF);        }    }
    // 斷開連接    shmdt(shm);
    return 0;}