linux mmap读写文件

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int main() {
    int fd = open("example.txt", O_RDWR);
    if (fd == -1) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    // 获取文件大小
    off_t file_size = lseek(fd, 0, SEEK_END);
    lseek(fd, 0, SEEK_SET);

    // 映射文件到内存
    void *addr = mmap(NULL, file_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (addr == MAP_FAILED) {
        perror("mmap");
        close(fd);
        exit(EXIT_FAILURE);
    }

    // 读取文件内容
    printf("File content: %s\n", (char *)addr);

    // 修改文件内容
    char *data = (char *)addr;
    data[0] = 'H';

    // 解除映射
    if (munmap(addr, file_size) == -1) {
        perror("munmap");
        close(fd);
        exit(EXIT_FAILURE);
    }

    close(fd);
    return 0;
}