1.1. Mac OS X Shells

Mac OS X comes with the Bourne-Again shell (bash) as the default user shell and also includes the TENEX C shell (tcsh), the Korn shell (ksh), and the Z shell (zsh). The bash, ksh, and zsh are sh-compatible. When tcsh is invoked through the csh link, it behaves much like csh. Similarly, /bin/sh is a hard link to bash, which also reverts to traditional behavior when invoked through this link (see the bash manpage for more information).

The version of bash that ships with Tiger has improved POSIX support over bash implementations that shipped with earlier releases of Mac OS X. Invoking bash with the -posix command-line option changes the default behavior of bash to comply with the POSIX 1003.2 standard in cases where the default behavior differs from this standard.

If you install additional shells , you should add them to /etc/shells. To change the Terminal's default shell, see "Customizing the Terminal," later in this chapter. To change a user's default shell (used for both the Terminal and remote console logins), see "Modifying a User" in Chapter 5.