High Quality Content by WIKIPEDIA articles! In computing, ren (or rename) is a command in various DOS, OS/2 and Microsoft Windows command line interpreters (shells) such as COMMAND.COM, cmd.exe, 4DOS/4NT and Windows PowerShell. It is used to rename files and in some implementations also directories. It is analogous to the Unix mv command. RT-11, RSX-11 and OpenVMS also provide the rename command which can be contracted to ren.