On standard Unix a login shell is choosen from a valid set of shells, listed in /etc/shells. And there is a standard unix command called chsh to change your shell, but some linux distribution use a GUI frontend to change that as well.
You can also find your login shell in the standard file /etc/passwd, but the Mac doesn't use that file (normally).
Not unlike Linux,there is more than one way to login or what kind of terminal program to use. But I believe that all use the same shell from /etc/passwd, at least on Unix. For the Mac, most commonly used are the X11/xterm, and the Terminal. By default /bin/bash is your login shell, and some complex choice of .bashrc, .profile, .bashrc_profile and .bashrc_login (see the man page) will determine which one(s) are read. But whatever we tried in one situation, even using the BASH_ENV environment variable, we could NOT get matlab to have miriad available in it's login shell (/bin/bash).
Switching to /bin/tcsh caused several challenges,but at least got us around the matlab issue:
- for X11 xterm you had to use the chsh command, but a reboot was required to really activate it. Not even kill X11, really a reboot.
- for Terminal there's a preference option where you need to pick /bin/tcsh as the login shell. After killing Terminal, restarting did show the tcsh prompt, but despite that, $SHELL would still show /bin/bash, even after a reboot.