/*********************************************************************************
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* Copyright: (C) 2025 LingYun IoT System Studio
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* All rights reserved.
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*
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* Filename: mycp.c
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* Description: This file a simple file copy command implement
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*
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* Version: 1.0.0(10/15/2025)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "10/15/2025 11:19:27 AM"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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int main(int argc, char *argv[])
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{
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struct stat src_stat;
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int src_fd = -1;
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int dst_fd = -1;
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char buf[512];
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ssize_t bytes_read;
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ssize_t to_read;
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off_t remaining;
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int rv = 0;
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/* 检查输入参数合法性, 此程序需要两个参数: 源文件和目标文件 */
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if (argc != 3)
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{
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fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);
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return 1;
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}
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/* 获取源文件的属性信息 */
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if (lstat(argv[1], &src_stat) == -1)
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{
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fprintf(stderr, "lstat file %s failure: %s\n", argv[1], strerror(errno));
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return 2;
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}
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/* 此程序只支持普通文件拷贝，不支持文件夹或其它文件 */
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if (!S_ISREG(src_stat.st_mode))
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{
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fprintf(stderr, "Error: %s is not a regular file\n", argv[1]);
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return 2;
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}
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/* 打以只读模式打开要拷贝的源文件 */
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src_fd = open(argv[1], O_RDONLY);
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if (src_fd == -1)
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{
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fprintf(stderr, "open file %s failure: %s\n", argv[1], strerror(errno));
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rv = 3;
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goto cleanup;
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}
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/* 创建要拷贝的目标文件，如果不存在就创建，权限位与源文件一致。如果文件已经存在则截取 */
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dst_fd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, src_stat.st_mode & 0777);
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if (dst_fd == -1)
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{
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fprintf(stderr, "open file %s failure: %s\n", argv[2], strerror(errno));
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rv = 3;
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goto cleanup;
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}
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/* 获取源文件的实际内容大小，并将其所有内容拷贝到目标文件中去 */
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remaining = src_stat.st_size;
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while (remaining > 0)
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{
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to_read = remaining > sizeof(buf) ? sizeof(buf) : remaining;
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bytes_read = read(src_fd, buf, to_read);
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if (bytes_read == -1)
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{
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fprintf(stderr, "read file %s failure: %s\n", argv[1], strerror(errno));
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rv = 3;
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goto cleanup;
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}
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if (bytes_read == 0)
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{
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fprintf(stderr, "Unexpected end of file\n");
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rv = 3;
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goto cleanup;
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}
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if (write(dst_fd, buf, bytes_read) != bytes_read)
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{
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fprintf(stderr, "write file %s failure: %s\n", argv[2], strerror(errno));
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rv = 3;
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goto cleanup;
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}
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remaining -= bytes_read;
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}
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/* 完成后关闭所有打开的文件描述符，如果出错也会goto到这里集中处理 */
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cleanup:
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if(src_fd >= 0)
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close(src_fd);
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if(dst_fd >= 0)
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close(src_fd);
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/* rv在定义时默认初始化为0表示成功，如果代码中有错误发生则会改变rv值，标识相应的错误原因 */
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return rv;
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}
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