Hmm... perhaps there should be some elaboration on the UNIX shells available to those who use Windows. Truth be told, I can't masquerade as a expert on this subject, having never even really used a Windows machine in my life. Anyhow, of those I know, there are plenty of options for those who want a UNIX prompt under Windows.
- Cygwin - Some of my friends use this, and some folks in MIT Center for Space Research recommend this as the next best thing to running Linux. I have used it, it is sluggish. But... I think this is your best bet if you want to have as close as possible to a UNIX environment under a Windows DOS evironment. It has sed, awk, bash, a version of mount, the gnu C compiler, among other things. Runs sshd and ftpd as well. Released under the General GNU Public License.
- U/Win -I don't know of anyone who uses U/Win, I think most settle for Cygwin, which seems to have a superior installer, and all around superior shell support. However, U/Win has very extensive library support - in fact, fork has been reprogrammed from the ground up, U/Win can even run the XFree86 and GNOME. At the DOS prompt, it has a port of the Korn Shell, but I here it is slower then Cygwin. U/Win, developed by AT&T, is free as a binary for educational purposes and private use, making it free as in beer, not free as in libre.
- Many of the GNU Utils have been ported to Windows out of the kindness of people's hearts. Mingw is a Cygnus port of GCC without the rest of Cygwin, making it rather convenient. There are of course ports of gzip, sed, awk, perl, python, su and many other utils that you can install into the DOS search paths. Just about everything that you can find stand alone is under the GPL, and this is probably the fastest option of all.
- Update: yerricde writes: "DJGPP is like Cygwin for DOS. It includes a compiler and binutils in the standard package; you can go on the FTP site and download a LOT of ported GNU packages, including bash, fileutils, and textutils (which comprise most common UNIX comands)." Thanks yerricde!
And those are the shells I know of. Please /msg me if I am wrong about licensing/speeds, and feel free to post other Shells for Windows.