mmap linux 文件

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.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");
        return 1;
    }

    struct stat sb;
    if (fstat(fd, &sb) == -1) {
        perror("fstat");
        close(fd);
        return 1;
    }

    char *addr = mmap(NULL, sb.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (addr == MAP_FAILED) {
        perror("mmap");
        close(fd);
        return 1;
    }

    // 修改文件内容
    addr[0] = 'H';
    addr[1] = 'e';
    addr[2] = 'l';
    addr[3] = 'l';
    addr[4] = 'o';

    if (msync(addr, sb.st_size, MS_SYNC) == -1) {
        perror("msync");
    }

    if (munmap(addr, sb.st_size) == -1) {
        perror("munmap");
    }

    close(fd);
    return 0;
}

if (msync(addr, sb.st_size, MS_SYNC) == -1) {
    perror("msync");
}

if (munmap(addr, sb.st_size) == -1) {
    perror("munmap");
}