Linux进程使用文件进行通信的常用方法

// 写入进程示例
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("comm_file.txt", O_WRONLY | O_CREAT, 0644);
    char message[] = "Hello from process 1";
    write(fd, message, sizeof(message));
    close(fd);
    return 0;
}

#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>

#define SHM_SIZE 4096

int main() {
    int fd = shm_open("/my_shm", O_CREAT | O_RDWR, 0666);
    ftruncate(fd, SHM_SIZE);
    
    char *shared_memory = mmap(NULL, SHM_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    strcpy(shared_memory, "Hello from shared memory");
    
    munmap(shared_memory, SHM_SIZE);
    close(fd);
    return 0;
}

// 创建命名管道
mkfifo /tmp/my_pipe

// 写入进程
int fd = open("/tmp/my_pipe", O_WRONLY);
write(fd, "Hello from named pipe", 21);
close(fd);

// 读取进程
int fd = open("/tmp/my_pipe", O_RDONLY);
char buffer[100];
read(fd, buffer, sizeof(buffer));
close(fd);

#include <sys/file.h>

int fd = open("shared_file.txt", O_RDWR);

// 获取共享锁
flock(fd, LOCK_SH);
// 读取文件内容
flock(fd, LOCK_UN);

// 获取排他锁
flock(fd, LOCK_EX);
// 写入新内容
flock(fd, LOCK_UN);

close(fd);

#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("data_file.txt", O_RDWR);
    struct stat sb;
    fstat(fd, &sb);
    
    char *mapped = mmap(NULL, sb.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    
    // 直接操作内存，就像操作文件内容一样
    strcpy(mapped, "This data is written via memory mapping");
    
    // 同步更改到文件
    msync(mapped, sb.st_size, MS_SYNC);
    
    munmap(mapped, sb.st_size);
    close(fd);
    return 0;
}