在linux环境下，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。

以下是使用系统调用read和write实现的文件复制程序：

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

#define BUFFER_SIZE 1024

int main(int argc, char *argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);
        return 1;
    }

    int source_fd = open(argv[1], O_RDONLY);
    if (source_fd == -1) {
        perror("open");
        return 2;
    }

    int dest_fd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (dest_fd == -1) {
        perror("open");
        return 3;
    }

    char buffer[BUFFER_SIZE];
    ssize_t nread;
    while ((nread = read(source_fd, buffer, BUFFER_SIZE)) > 0) {
        ssize_t nwritten = write(dest_fd, buffer, nread);
        if (nwritten == -1) {
            perror("write");
            return 4;
        }
    }

    if (nread == -1) {
        perror("read");
        return 5;
    }

    close(source_fd);
    close(dest_fd);

    return 0;
}

以下是使用文件的库函数fread和fwrite实现的文件复制程序：

#include <stdio.h>

#define BUFFER_SIZE 1024

int main(int argc, char *argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);
        return 1;
    }

    FILE *source_fp = fopen(argv[1], "rb");
    if (source_fp == NULL) {
        perror("fopen");
        return 2;
    }

    FILE *dest_fp = fopen(argv[2], "wb");
    if (dest_fp == NULL) {
        perror("fopen");
        return 3;
    }

    char buffer[BUFFER_SIZE];
    size_t nread;
    while ((nread = fread(buffer, 1, BUFFER_SIZE, source_fp)) > 0) {
        size_t nwritten = fwrite(buffer, 1, nread, dest_fp);
        if (nwritten != nread) {
            perror("fwrite");
            return 4;
        }
    }

    if (ferror(source_fp)) {
        perror("fread");
        return 5;
    }

    fclose(source_fp);
    fclose(dest_fp);

    return 0;
}