CheckNotExist check if the file exists.

CheckPermission check if the file has permission.

Find files older than overDate.

GetExt get the file ext.

GetSize get the file size.

IsNotExistMkDir create a directory if it does not exist.

Judement file modtime older than overDate.

MkDir create a directory.

MustOpen maximize trying to open the file.

Open a file according to a specific mode.