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Shells, and More Shells
the program that prompts you for commands, interprets what you type in, and
runs that. It can handle job
you, letting you run utilities in the background while another runs in the
foreground. It can do completion,
saving you keystrokes. (The original developers of UNIX
keystrokes. This explains the terse syntax of C, and the lack of vowels/use
of acronyms in the basic commands -- eg.
not to mention
the original shell.
the Beginning There Was ...UNIX
named after its author, Steve Bourne of Bell Labs. Written for Version
it is a rather simple shell, best left for non-interactive scripts.
to the ShoreLater,
during the development of BSD
the University of California at Berkeley, Bill Joy wrote
New features included C-like control statements, job
This became the default login shell on BSD systems, while the Bourne
used for scripts. Even today, most users of the C shell & its derivatives write
scripts in Bourne.
not without bugs. Rather than waiting for UCB, users submitted bug fixes and
new features to the net, including TENEX-style command completion. The result
(See the man
a list of over four dozen authors and contributors.) If you like the C
the shell for you.
Maize of FeaturesPopping
back to Bell Labs, we find the KornShell,
written by David Korn. Using a syntax based on the Bourne shell, it adds the
features that made the C shell so popular. The KornShell is only available
in System V -- and was an extra cost add on prior to Release 4. Due to its
limited availability -- and the fact that you needed a full AT& source license
to get the KornShell's source -- Eric Gisin took the public domain System 7
version of the Bourne Shell and added on most of the features of the KornShell.
The result, pdksh,
is shipped by BSDI
This is our default login shell.
is not UNIXSeeing
how well the KornShell
to its predecessors, the folks behind POSIX made it their standard shell.
comes the Free Software Foundation, wanting a free, POSIX compatable system.
Part of that is
Bash has many of the same features as the real KornShell,
and is recommended for those who favour the Bourne syntax in their login shells.
9 From Outer SpaceRather
than porting the Bourne
Tom Duff wrote
and then published a paper on it. Byron Rakitzis liked it enought to implement
it under UNIX.
Not having the historical garbage, many people find it to be a cleaner shell.
We don't, currently, have
or its successor,
Alphabet Ends With ZedLast
on our list of shells is Paul Falstad's entry,
Similar to but not completely compatable with Bourne,
to expand regularly. There can be great power in an excess of features -- if
can learn them all. (Cf. PL/1.)
Do I Ever ChooseFirst,
you want to look at the file
see what choices you have for your login shell. UNIX
limit you to choosing a shell from
security reasons -- and also to ensure that you can log in next time....
go read the excellent
you can use our web-based
user account information management page
change your password settings, shell, or handle. The change will go into effect
within 30 minutes.
revised August 3, 2000