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!
   ",__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]
   ", 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
   ", __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
   ");
                   exit(EXIT_FAILURE);
                   break;
               
               default:
                   fprintf(stderr, "%s(%d): file type error
   ", __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", src, entp->d_name);
           sprintf(dest_buf, "%s/%s", 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