IPC程序例子 一

这里只是简单的举例来说明ipc通讯机制相关函数用法：

管道

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#include <unistd.h>

int pipe(int pipefides[]);

举例：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/errno.h>

#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>

#define BUF_SIZE 50

int main() {
    pid_t pid;
    char buf[BUF_SIZE] ={0};
    int pfds[2] = {-1, -1};
    if (pipe(pfds) < 0) {
        perror("pipe error");
        exit(0);
    }
    if ((pid = fork()) < 0) {
        perror("fork error");
        exit(0);
    }

    if (pid == 0) {
        close(pfds[1]);
        int len = 0;
        while (len == 0) {
            read(pfds[0], buf, BUF_SIZE);
            len = strlen(buf);
        }
        printf("%s\n", buf);
        close(pfds[0]);
        exit(0);
    }
    
    close(pfds[0]);
    strcpy(buf, "This is a pipe test!");
    write(pfds[1], buf, BUF_SIZE);
    close(pfds[1]);
    sleep(2);
    int status;
    waitpid(-1, &status, 0);
    if (WIFEXITED(status)) {
        printf("child exit status %d", WEXITSTATUS(status));
    }
    return 0;
}

运行结果：

This is a pipe test!
child exit status 0
运行 FINISHED; 退出值0; 实时:  2s; 用户:  0ms; 系统:  0ms

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有名管道

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#include<sys/ipc.h>

#include <sys/stat.h>

int mkfifo (__const char *__path, __mode_t __mode);

举例：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/errno.h>

#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>

#include <fcntl.h>
#include <sys/stat.h>

#define BUF_SIZE 50

#define PIPE_FILE_PATH          "/tmp/pipe0"

int main() {

    unlink(PIPE_FILE_PATH);
    int fd;
    pid_t pid;
    char buf[BUF_SIZE] = {0};
    if (mkfifo(PIPE_FILE_PATH, 0666) < 0) {
        perror("mk fifo error");
        exit(0);
    }
    if ((pid = fork()) < 0) {
        perror("fork error");
        exit(0);
    }
    if (pid == 0) {
        int len = 0;
        if ((fd = open(PIPE_FILE_PATH, O_RDONLY)) < 0) {
            perror("open read failed");
            exit(0);
        }
        while (len == 0) {
            if (read(fd, buf, BUF_SIZE) < 0) {
                exit(0);
            }
            len = strlen(buf);
        }
        printf("%s\n", buf);
        close(fd);
        exit(0);
    }

    if ((fd = open(PIPE_FILE_PATH, O_WRONLY)) < 0) {
        perror("open write failed");
        exit(0);
    }
    strcpy(buf, "This is a pipe test!");
    write(fd, buf, BUF_SIZE);
    close(fd);
    sleep(2);
    int status;
    waitpid(-1, &status, 0);
    if (WIFEXITED(status)) {
        printf("child exit status %d", WEXITSTATUS(status));
    }
    return 0;
}

运行结果：

This is a pipe test!
child exit status 0
运行 FINISHED; 退出值0; 实时:  2s; 用户:  0ms; 系统:  0ms

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类似命令行管道（cat /etc/passwd|grep 'root'）

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#include <stdio.h>

FILE *popen (__const char *__command, __const char *__modes)

int pclose (FILE *__stream);

举例说明：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>


#include <unistd.h>
#include <sys/types.h>
#include <sys/errno.h>


int main() {


    char buf[2048];
    FILE *pipe = popen("cat /etc/passwd","r");
    fgets(buf,2048,pipe);//只读取一行
    puts(buf);
    return 0;
}

运行结果：

root:x:0:0:root:/root:/bin/bash
运行 FINISHED; 退出值0; 实时:  10ms; 用户:  0ms; 系统:  0ms

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消息队列

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#include<sys/ipc.h>

#include<sys/msg.h>

int     msgctl (int msqid, int cmd, struct msqid_ds *buf);
int     msgget (key_t key, int msgflg);
ssize_t msgrcv (int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);
int     msgsnd (int msqid, const void *msgp, size_t msgsz, int msgflg);

举例：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>


#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/errno.h>

#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>

#define MSG_KEY 1000ll
#define BUF_SIZE 50

typedef struct {
    long msg_type;
    char text[BUF_SIZE];
} Message;

#define MSG_TYPE 0x100al

int main() {

    int msgid;
    Message msg = {0};
    if ((msgid = msgget(MSG_KEY, IPC_CREAT | 0666)) < 0) {
        perror("creat msg id as 1000 error");
        exit(0);
    }
    pid_t pid;
    if ((pid = fork()) < 0) {
        perror("fork error");
        exit(0);
    }
    if (pid == 0) {
        msg.msg_type = MSG_TYPE;
        memset(msg.text, 0, sizeof (msg.text));
        strcpy(msg.text, "This is a test for msg queue!");
        msgsnd(msgid, &msg, BUF_SIZE, 0);
        exit(1);
    }
    if (waitpid(-1, NULL, 0) < 0) {
        perror("wait error");
    }
    sleep(2);
    msgrcv(msgid, &msg, BUF_SIZE, MSG_TYPE, 0);
    printf("%s\n", msg.text);
    msgctl(msgid, IPC_RMID, NULL);
    return 0;
}

运行结果：

This is a test for msg queue!
运行 FINISHED; 退出值0; 实时:  2s; 用户:  0ms; 系统:  0ms

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