linux 调用两次mmap

#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_RDONLY);
    if (fd == -1) {
        perror("open");
        return 1;
    }

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

    size_t file_size = sb.st_size;
    size_t half_size = file_size / 2;

    void *addr1 = mmap(NULL, half_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if (addr1 == MAP_FAILED) {
        perror("mmap");
        close(fd);
        return 1;
    }

    void *addr2 = mmap(NULL, half_size, PROT_READ, MAP_PRIVATE, fd, half_size);
    if (addr2 == MAP_FAILED) {
        perror("mmap");
        munmap(addr1, half_size);
        close(fd);
        return 1;
    }

    // 处理映射的内存区域
    printf("First half: %.*s\n", (int)half_size, (char *)addr1);
    printf("Second half: %.*s\n", (int)half_size, (char *)addr2);

    // 清理资源
    munmap(addr1, half_size);
    munmap(addr2, half_size);
    close(fd);

    return 0;
}