实验七：文件系统拷贝功能模拟 用C语言编写文件复制程序。分别使用系统调用read (fd,buf,nbytes)、write(fd, buf,nbytes)和文件的库函数fread(buf,size,nitems,fp)、fwrite(buf,size,nitems,fp)，编写一个文件复制程序。

以下是一个使用系统调用的文件复制程序示例：

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

#define BUFFER_SIZE 4096

int main(int argc, char *argv[]) {
    int input_fd, output_fd, bytes_read, bytes_written;
    char buffer[BUFFER_SIZE];

    if (argc != 3) {
        printf("Usage: %s <input_file> <output_file>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    input_fd = open(argv[1], O_RDONLY);
    if (input_fd == -1) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    output_fd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (output_fd == -1) {
        perror("open");
        exit(EXIT_FAILURE);
    }

    while ((bytes_read = read(input_fd, buffer, BUFFER_SIZE)) > 0) {
        bytes_written = write(output_fd, buffer, bytes_read);
        if (bytes_written != bytes_read) {
            perror("write");
            exit(EXIT_FAILURE);
        }
    }

    if (bytes_read == -1) {
        perror("read");
        exit(EXIT_FAILURE);
    }

    if (close(input_fd) == -1) {
        perror("close");
        exit(EXIT_FAILURE);
    }

    if (close(output_fd) == -1) {
        perror("close");
        exit(EXIT_FAILURE);
    }

    return 0;
}

以下是一个使用文件的库函数的文件复制程序示例：

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

#define BUFFER_SIZE 4096

int main(int argc, char *argv[]) {
    FILE *input_file, *output_file;
    char buffer[BUFFER_SIZE];
    size_t bytes_read, bytes_written;

    if (argc != 3) {
        printf("Usage: %s <input_file> <output_file>\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    input_file = fopen(argv[1], "rb");
    if (input_file == NULL) {
        perror("fopen");
        exit(EXIT_FAILURE);
    }

    output_file = fopen(argv[2], "wb");
    if (output_file == NULL) {
        perror("fopen");
        exit(EXIT_FAILURE);
    }

    while ((bytes_read = fread(buffer, 1, BUFFER_SIZE, input_file)) > 0) {
        bytes_written = fwrite(buffer, 1, bytes_read, output_file);
        if (bytes_written != bytes_read) {
            perror("fwrite");
            exit(EXIT_FAILURE);
        }
    }

    if (ferror(input_file)) {
        perror("fread");
        exit(EXIT_FAILURE);
    }

    if (fclose(input_file) != 0) {
        perror("fclose");
        exit(EXIT_FAILURE);
    }

    if (fclose(output_file) != 0) {
        perror("fclose");
        exit(EXIT_FAILURE);
    }

    return 0;
}