Currently at version 0.70, and seeming likely to stay there permanently, lsh is a shell for Linux (or other unix-like) systems written by Marc Welz that acts in many ways like the old MS-DOS COMMAND.COM, even including many builtin commands like dir, pause, prompt, and all the standard DOS file manipulation commands. Take, for example, the root directory on my laptop:

carson@peregrine:~ $ lsh

C:\>dir

 Volume in drive C is too loud
 Volume Serial Number is EF53-00FF
 Directory List

root                09-15-02   2:35p
boot                07-19-02   0:50p
tmp                 09-27-02   1:16p
lib                 08-31-02   7:16p
usr                 09-20-02   5:19p
sbin                09-25-02   2:10a
etc                 09-27-02   1:12p
var                 09-25-02   3:14p
bin                 09-09-02   3:26p
dev                 09-27-02   1:56a
home                06-27-02   5:14p
mnt                 06-17-02   0:07a
proc                09-27-02   1:55a
floppy              06-17-02   0:08a
cdrom               09-12-02   7:59p
initrd              06-17-02   0:08a
music               09-25-02   2:22a
cdrom0              09-12-02   7:59p
       18 files            0 bytes
                  3428933632 bytes free

C:\>cd home

C:\HOME>

As you can see, even the standard unix directory separator, the forward slash, is translated to a backslash. Forward slashes are, as in DOS, interpreted as precursors to command-line options (at least for the built-in commands). On execution, it reads /etc/autoexec and ~/.autoexecrc for its options.

lsh is distributed under the GNU General Public License. Source code used to be available at http://people.cs.uct.ac.za/~mwelz/lsh.html but this now gives a 404. Google turns up no current website as far as I can find. Debian and Ubuntu users, however, can apt-get install lsh--although why they'd really want to is beyond me. Users of RPM-based distributions may also find binaries from their vendor.

Completely unrelatedly, lsh is also an attempt to create a GPL-licensed implementation of the SSHv2 protocol. I haven't used it, but from what I understand, it acts pretty much the same as the official ssh or OpenSSH do. See http://www.lysator.liu.se/~nisse/lsh/ for more info; Debian users can apt-get install lsh-client lsh-server—as above, RPM packages may (or may not) be available from your respective vendor.