There is already one answered the question at Best way to use a shell with Cygwin in Windows 7. That is to start Cygwin with C:\cygwin\bin\mintty.exe -With that $SHELL = /bin/shHow can I launch mintty with /usr/bin/bash as default shell?
Using mintty as default terminal on Cygwin and default shell as bash
terminal;cygwin
There are several different ways to do it:Specify bash as a command-line argument to mintty, as mentioned by Salton.Set the Windows SHELL environment variable to /usr/bin/bash.Make sure you have an /etc/passwd (see mkpasswd(1)) in your Cygwin environment, and set the shell for your UID to /usr/bin/bash. Cygwin doesn't supply a chsh or usermod command, so you'll probably have to edit the file by hand if you want to use this method.From the mintty(1) manpage:INVOCATION   If a program name is supplied on the command line, this is executed   with any additional arguments given.  Otherwise, mintty looks for a   shell to execute in the SHELL environment variable.  If that is not   set, it reads the user's default shell setting from /etc/passwd.  As a   last resort, it falls back to /bin/sh.  If a single dash is specified   instead of a program name, the shell is invoked as a login shell.