CheckFileExist 파일이 있는지 체크.

CheckFileNotExist check if the file exists.

CheckPermission check if the file has permission.

GetExt get the file ext, include dot(.) abc.txt --> .txt.

GetSize get the file size.

GetCurrentWorkDirectory get current working directory.

MakeDir create a directory.

MkDirIfNotExist create a directory if it does not exist.

MustOpen maximize trying to open the file.

Open a file according to a specific mode.

RemoveDirIfExist remove directory if exist.