4.2 Features of Available Shells

This section is excerpted from Shell Choice, A shell comparison (dated September 28, 1994) by Arnaud Taddei of CERN. His eleven-page document contains a brief description of the six major shells and provides an excellent comparison of features between the shells. It is available on the Web at http://consult.cern.ch/writeup/shellchoice.

Of the six major shells, four are in the Bourne family: sh, ksh, bash, and zsh; and two are in the Berkeley/C family: csh, tsch.

The most up-to-date shells are tcsh (Berkeley/C), and bash and zsh (Bourne). These are also the three shells that are public domain (as opposed to vendor-supported). The public domain shells are the same on all platforms, which is not true of vendor shells. This is desirable when attempting to homogenize user environments. Note that zsh is not supported at Fermilab.

Some of the common features of these newer shells are:

• specific startup files
• startup files are the same for any platform
• specific shell variables
• specific built-in commands

The tcsh is essentially an enhanced csh. Some additional features of the tcsh are:

• enhanced completion[12] mechanism (programmable for commands, file names, variable names, user names, etc.)
• multiline editing capabilities (command line editing using emacs or vi-style key bindings)
• enhanced file expression syntax
• spelling correction (see section 5.3)
• enhanced prompt
• step up/down through history list

The following table should give you an idea of the virtues of each of the shells supported at Fermilab. It is adapted from one in Taddei's document referenced above. More complete feature lists for all the shells can be found there.

++

good

+

existing

-

weak

--

absent

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