LR File Manipulation Functions examples

例子：The following example uses mkdir to create a new directory,xyz. It then moves to the new directory.

#ifdef unix

char new_dir[]="/tmp/xyz"

#else

char new_dir[]="C:\\xyz";

#endif

//加载外部函数

lr_load_dll("D:\Accessdll.dll");

//动态文件中包含如下函数

/*int file_exists(char *filename)

return (access(filename,0)==0);*/

//判断目录是否存在可以用

if(file_exists(new_dir)) {

lr_output_message("%s directory exists",new_dir);

rmdir(new_dir);

}

//在root目录下创建xyz目录，并设置其为当前目录

if (mkdir(new_dir)) {

        lr_output_message("Create directory %s failed",new_dir);

        return -1;

}

else

lr_output_message("Created new directory %s",new_dir);

//变更目录

if (chdir(new_dir)) {

        lr_output_message("Unable to change to dir %s",new_dir);

        return -1;

}

else

lr_output_message("Changed to new dir %s",new_dir);*/

例子：The following example uses chdrive to move to all available drives on the file system.

It saves the original drive in curdrive, so it can be restored later.

int drive,curdrive;

//获取当前的盘符

curdrive=getdrive();

lr_output_message("Available drives are:");

//循环读取本系统中所有的盘符

for(drive=1;drive<=26;drive++)

        if(!chdrive(drive))

          lr_output_message("%c:",drive + 'A'-1);

        chdrive(curdrive);

例子：This example uses getcwd to save the current directory, before moving to a new directory.

It then moves back to the first directory.

#define DIR_LEN 512

char original_dir[DIR_LEN];

#ifdef unix

char new_dir[]="/tmp";

#else

char new_dir[]="C:\\";

#endif

//getcwd如果成功返回当前的字符串,否则返回空值

if (!getcwd(original_dir,DIR_LEN)) {

lr_output_message("getcwd error");

return -1;

}

else

lr_output_message("The current dir is: %s",original_dir);

if (chdir(new_dir)) {

        lr_output_message("Unable to locate directory:%s",new_dir);

        return -1;

}

else

lr_output_message("Changed dir to %s",new_dir);

if (chdir(original_dir)) {

        lr_output_message("Cannot move back to #s",original_dir);

        return -1;

}

else

lr_output_message("Move back to %s",original_dir);

例子：/*The system function executes a dir command.

The output of the command is written (using `>) to the newly created file.

The content of the file should be a list of the contents of the C drive.

It then deletes the new file with remove*/

char filename[1024],command[1024];

char new_dir[]="C:\\xyz";

extern int errno;

//在root下创建xyz目录，并设为当前目录

if(mkdir(new_dir))

        lr_output_message("Create directory %s failed",new_dir);

else

lr_output_message("Created new directory %s",new_dir);

//filename赋值为C:\xyz\newfile.txt

sprintf(filename,"%s\\%s",new_dir,"newfile.txt");

//command赋值为dir C:\ > C:\xyz\newfile.txt /w

sprintf(command,"dir /b C:\\ > %s /w",filename);

//运行命令：dir /b C:\ > C:\xyz\newfile.txt /w

system(command);

lr_output_message("Create new file %s",filename);

//删除已经建立的文件

if (remove(filename) == 0)

       lr_output_message ("Removed new file %s", filename);

   else

       lr_output_message ("Unable to remove %s error %d", filename, errno);

例子：/*在windows系统,用LR中的system函数执行系统命令,在LR中利用C函数建立文件，写文件，读文件。
　　主要相关函数：sprintf/fopen/fgetc/fread/fclose*/
  int count,total=0,i;
     char buffer[1000];
     long file_stream;
     char filename[1024], command[1024],line[100];
     char new_dir[] = "C:\\test";
     if (mkdir(new_dir))
          lr_output_message("Create directory %s failed", new_dir);
     else
          lr_output_message("Created new directory %s", new_dir);
     sprintf (filename, "%s\\%s", new_dir, "newfile.txt");
     sprintf (command, "dir /b c:\\ > %s /w", filename );
     system(command);//通过DOS管道命令创建TXT文件
     lr_output_message("Created new file %s", filename);
  //以只读方式打开文件
   if((file_stream=fopen(filename,"r"))==NULL)
       {
       lr_error_message("can not open %s",filename);
       return -1;
   }
   //逐行读取TXT文件中的字符串
   for(i=1;i<10;i++)
    {
       if (fgets(line, 100, file_stream) == NULL)
          lr_output_message("fgets error" );
     else 
          lr_output_message( "The line%d is: %s",i,line);
    }
//如果已经到文件结尾，计算总得字节数
    while(!feof(file_stream))
              {
      count=fread(buffer,sizeof(char),1000,file_stream);
       lr_output_message("%3d read",count);

 //Checks if any error has occurred during file I/0.
    if(ferror(file_stream))
              {
    lr_output_message("error reading file %s",filename);
    break;
        }
//把计算后的Count赋值给total
   total+=count;
        }
      lr_output_message("Total number of bytes read = %d",total);

     if(fclose(file_stream))//关闭文件
      lr_error_message("Error closing file %s",filename);

File Manipulation functions.rar(14.5 KB)