All of the Linux distributions included with this book use bash as the default shell, with the exception
of some bootable Linux distributions, which use the ash shell instead.
Using tcsh (and Earlier csh) Shells
The tcsh shell is the open source version of the C shell (csh). The csh shell was created by Bill Joy
and used with most Berkeley UNIX systems (such as those produced by Sun Microsystems) as the
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Running Commands from the Shell 2
default shell. Features from the TENEX and TOPS-20 operating systems (used on PDP-11s in the
1970s) that are included in this shell are responsible for the T in tcsh.
Many features of the original csh shell, such as command-line editing and its history mechanism,
are included in tcsh as well as in other shells. While you can run both csh and tcsh on most Linux
systems, both commands actually point to the same executable file. In other words, starting csh
actually runs the tcsh shell in csh compatibility mode.
Using ash
The ash shell is a lightweight version of the Berkeley UNIX sh shell. It doesn??™t include many of the
sh shell??™s basic features, and is missing such features as command histories. Kenneth Almquist created
the ash shell.
The ash shell is a good shell for embedded systems that have fewer system resources available.
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