Linux 命令 "cp" 代码实现简介

本blog主要是模仿Linux的cp命令的功能，未实现参数，只是基础功能部分。
本文的主要目的在于练习 文件流 和 目录流 中的函数的使用。

主要功能包括两种：

• 源文件属性为文件，拷贝到其它文件(内容复制)或目录(作为目录子文件)
• 源文件属性为目录，拷贝到其它目录(作为子目录存在)

其实现的流程图如下所示：

本copy我们通过三个文件来实现：

• main.c：流程的实现
• copy.c：拷贝功能的实现
• copy.h：必要的头文件

1. main.c

   /*********************************************************
   * File name:
   * Description:
   * Author: Jimmy_Nie
   * Version Modify Time
   * v1.0 creat 2017-09-12
   *
   *********************************************************/

   include "copy_file.h"

   int main(int argc, char *argv[])
   {
   //Check the arguments
   if( 3 != argc)
   {
   printf("%s(%d): arguments error!\n",FILE, LINE);
   exit(EXIT_FAILURE);
   }

   //check the source file is a file or a directory
   struct stat src_stat;

   //destination file check
   struct stat dest_stat;

   //If source is a file
   if( FILES == check_file(argv[1], &src_stat) )
   {
   FILE_ENUM dest_enum;
   dest_enum = check_file( argv[2], &dest_stat );

   char cmd[100] = "";
   char ch;

   switch(dest_enum)
   {
   case NOT_EXIST:
   sprintf(cmd, "touch %s", argv[2]);
   system( cmd );

   check_file( argv[2], &dest_stat );
   cp_file(argv[1], argv[2], &dest_stat);

   break;

   case DIRECTORY:
   cp_file(argv[1], argv[2], &dest_stat);
   break;

   case FILES:
   fprintf(stdout, "Overwrite the dest file %s, [y/n]\n", argv[2]);
   ch = getchar();

   if( ch == 'Y' || ch == 'y' )
   {
   cp_file(argv[1], argv[2], &dest_stat);
   }
   else
   exit(0);

   break;
   default:
   fprintf(stderr, "%s(%d): file type error\n", FILE, LINE);
   }
   }

   //If source file is a directory
   else if( DIRECTORY == check_file(argv[1], &dest_stat) )
   {
   FILE_ENUM dest_enum;
   dest_enum = check_file( argv[2], &dest_stat );

   char cmd[100] = "";

   switch(dest_enum)
   {
   case NOT_EXIST:
   sprintf(cmd, "mkdir -p %s", argv[2]);
   system( cmd );
   cp_dir(argv[1], argv[2] );
   break;

   case DIRECTORY:
   cp_dir(argv[1], argv[2]);
   break;

   case FILES:
   fprintf(stderr, "Can't copy a directory to a file\n");
   exit(EXIT_FAILURE);
   break;

   default:
   fprintf(stderr, "%s(%d): file type error\n", FILE, LINE);
   break;
   }
   }

   return 0;
   }

2. copy.c

   include "copy_file.h"

   FILE_ENUM check_file(char *var, struct stat *st)
   {
   if( stat(var, st) ) //if stat function error(renturn nonzero)
   {
   if( ENOENT == errno) //No such file or directory
   {
   return NOT_EXIST;
   }
   else
   {
   perror("stat");
   exit(EXIT_FAILURE);
   }
   }

   else // stat() ok, no error
   {
   //check file attr(dir or file)
   if( S_ISDIR(st->st_mode ))
   return DIRECTORY;
   else if( S_ISREG(st->st_mode) )
   return FILES;
   else
   {
   fprintf(stderr, "%s(%d):file type error", FILE , LINE);
   exit(EXIT_FAILURE);
   }
   }
   }

   //-----------------------------------------------------

   int cp_file(char *src_var, char *dest_var, struct stat *st)
   {
   FILE *src = NULL;
   FILE *dest = NULL;

   if( S_ISREG(st->st_mode) ) //if dest is file
   {
   //1. open src and dest file
   if( NULL == (src = fopen(src_var, "r")) )
   {
   perror("fopen");
   exit(EXIT_FAILURE);
   }

   if( NULL == (dest = fopen(dest_var, "w+")) )
   {
   perror("fopen");
   exit(EXIT_FAILURE);
   }

   //2. copy the context from src to dest
   char buf[1024];
   int num;

   while(1)
   {
   // if at the end of file or an error occured
   if( 1024 != (num = fread(buf, 1,1024, src)))
   {
   if( !feof(src))
   {
   perror("fread");
   exit(EXIT_FAILURE);
   }

   else
   {
   fwrite(buf, 1, num, dest);
   fclose(dest); //3. close dest file
   break;
   }
   }
   fwrite(buf, 1, 1024, dest);

   }

   //3. close src file
   fclose(src);
   return 0;
   }

   if( S_ISDIR(st->st_mode) )
   {
   char buf[100]="";

   //make the relative path to absolute path
   strncpy(buf, dest_var, sizeof(dest_var));
   strcat(buf, src_var);

   //if dest file doesn't exist, creat it first
   char cmd[100]="";
   sprintf(cmd, "touch %s",buf);
   system(cmd);

   struct stat new_dest_stat;

   if( stat(buf, &new_dest_stat))
   {
   perror("stat");
   exit(EXIT_FAILURE);
   }

   cp_file(src_var, buf, &new_dest_stat);
   }

   return 0;
   }

   //----------------------------------------------
   //if src file is a dir
   int cp_dir(char *src, char *dest)
   {
   DIR *dirp = NULL;

   //1. open the dir
   if( NULL == (dirp = opendir(src)) )
   {
   perror("opendir");
   exit(EXIT_FAILURE);
   }

   struct dirent *entp = NULL;

   //2. read the dir
   while( NULL != (entp = readdir(dirp))) //read the dir context
   {
   if( 0 == (strcmp(entp->d_name,"..")) || 0 == (strcmp(entp->d_name, ".")))
   {
   continue;
   }

   char src_buf[100] = "";
   char dest_buf[100] = "";

   sprintf(src_buf, "%s/%s\0", src, entp->d_name);
   sprintf(dest_buf, "%s/%s\0", dest, entp->d_name);

   struct stat src_stat;

   if( stat(src_buf,&src_stat) )
   {
   perror("stat");
   exit(EXIT_FAILURE);
   }

   if( S_ISREG(src_stat.st_mode) )
   {
   cp_file(src_buf, dest_buf, &src_stat);
   }

   else if( S_ISDIR(src_stat.st_mode) )
   {
   if( -1 == mkdir(dest_buf, src_stat.st_mode) )
   {
   perror("mkdir");
   exit(EXIT_FAILURE);
   }

   cp_dir(src_buf, dest_buf); //if subdir, recursive call itself
   }
   }

   return 0;
   }

3. copy.h

   ifndef COPY_H

   define COPY_H

   include <stdio.h>

   include <unistd.h>

   include <sys/types.h>

   include <sys/stat.h>

   include <errno.h>

   include <string.h>

   include <dirent.h>

   include <stdlib.h>

   typedef enum
   {
   NOT_EXIST=1,
   DIRECTORY,
   FILES
   }FILE_ENUM;

   extern FILE_ENUM check_file(char *var, struct stat *st); //检查文件类型

   extern int cp_file(char *src_var, char *dest_var, struct stat *st); //copy文件

   extern int cp_dir(char *src, char *dest); //copy目录

   endif