linux进程间通信实例代码

以下是一个使用Linux进程间通信（IPC）机制的示例代码，包括使用管道（pipe）、共享内存（shared memory）和信号量（semaphore）进行进程间通信。

1. 使用管道（pipe）进行进程间通信：

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

#define BUFFER_SIZE 25

int main()
{
    int fd[2];
    pid_t pid;
    char write_msg[BUFFER_SIZE] = "Greetings";
    char read_msg[BUFFER_SIZE];

    if (pipe(fd) == -1)
    {
        fprintf(stderr, "Pipe failed");
        return 1;
    }

    pid = fork();

    if (pid < 0)
    {
        fprintf(stderr, "Fork failed");
        return 1;
    }

    if (pid > 0)  // Parent process
    {
        close(fd[0]);
        write(fd[1], write_msg, BUFFER_SIZE);
        close(fd[1]);
    }
    else  // Child process
    {
        close(fd[1]);
        read(fd[0], read_msg, BUFFER_SIZE);
        printf("Received message: %s\n", read_msg);
        close(fd[0]);
    }

    return 0;
}

2. 使用共享内存（shared memory）进行进程间通信：

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

#define SHM_SIZE 1024

int main()
{
    int shmid;
    key_t key = 1234;
    char *shm, *s;

    if ((shmid = shmget(key, SHM_SIZE, IPC_CREAT | 0666)) < 0)
    {
        perror("shmget");
        exit(1);
    }

    if ((shm = shmat(shmid, NULL, 0)) == (char *) -1)
    {
        perror("shmat");
        exit(1);
    }

    printf("Enter message: ");

    for (s = shm; (*s = getchar()) != '\n'; s++)
        ;

    *s = '\0';

    printf("You entered: %s\n", shm);

    shmdt(shm);

    return 0;
}

3. 使用信号量（semaphore）进行进程间通信：

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

#define MAX_RETRIES 10

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

int main()
{
    key_t key = 1234;
    int semid, semval;
    union semun arg;
    struct sembuf sembuf;

    if ((semid = semget(key, 1, IPC_CREAT | 0666)) == -1)
    {
        perror("semget");
        exit(1);
    }

    arg.val = 1;

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

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

    printf("Semaphore value before decrement: %d\n", semval);

    sembuf.sem_num = 0;
    sembuf.sem_op = -1;
    sembuf.sem_flg =