cross
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response 4 of 35:
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Sep 19 04:01 UTC 2006 |
The Bourne Shell: /bin/sh (or direct replacement)
The standard 7th Edition shell. Originally, quite a weird implementation
(it allocated memory by trapping signals and increasing the size of the data
segment instead of just calling malloc, and used preprocessor symbols to
make the code look like a sort of weird variant of ALGOL). Most modern
versions contrain job control.
The C-Shell: /bin/csh
Developed at Berkeley by Bill Joy. Descended from the 6th Edition shell
and, while it has some useful features (job control, command history and
associated syntax for its manipulation, file name completion, the use of the
tilde (~) to refer to a user's home directory [default current user]), it
lacks some of the better ones incorporated into the Bourne shell (like the
ability to redirect individual file descriptors. E.g., for output, you can
either redirect stdout (>) or stdout and stderr together (>&). In
particular, you cannot easily redirect stderr independently of stdout). CSH
was designed to have a "C-like" syntax, but I've never really understood
this; it doesn't look particularly C-like to me. At this stage, mostly
historical.
The Tenex C-Shell: tcsh (non-standard)
This took the C shell, and added to it "Tenex-style" command and filename
completion, and command line editting using vi or emacs style keybindings
(similar to GNU's readline library). Much more usable than pure C shell
once you get the hang of it.
The Korn Shell: /bin/ksh
Developed at AT&T by David Korn and others. Derived from the Bourne shell,
but with command recall facilities similar to CSH and many other advanced
features (a command-line editting facility with either emacs or vi modes,
etc). Supposedly the basis for the POSIX shell, though most systems ship
some sort of Bourne-like shell or derivitive, or the C shell.
The Bourne-again Shell: bash (non-standard)
The GNU reimplementation of the Bourne shell, with lots of new features and
enhacements. It features command and filename completion, command line
editing, job control, command history and recall with editting, etc. Pretty
much standard on Linux, much more capable than the original Bourne shell,
and containing pretty much the union of features of all the shells
previously mentioned. Often criticized for being *too* big and
correspondingly slow.
The 9th Edition Shell: rc (non-standard)
A brand new shell with a syntax reminiscent of the Bourne shell, but far
more regular. This one actually looks kinda like C; it's far simpler than
any of the others listed here, but remains powerfl. It has been adopted as
the standard shell under Plan 9. Cedes things like job control, history,
command history and command line editing to other programs (under Plan 9,
the window system mostly).
The Extensible shell: es (non-standard)
Based on a Unix-only clone of rc, featuring an embedded Scheme interpreter.
Interesting, but not hugely popular. A patch to add job control exists.
The Z shell: zsh (non-standard)
Another Bourne-derived shell, quite full-featured. Nate and Jeff are both
users of zsh; perhaps they can comment further.
I think that's most of the biggies.
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twenex
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response 5 of 35:
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Sep 19 15:14 UTC 2006 |
Some of the BSDs (and probably some of the Linux distributions) also used
cut-down or statically-linked shells such as ash, either for system repair
or as the default shell for root (the administrator account).
ZSH has some nifty features, such as being able to go to a directory by typing
its name alone, instead of after "cd", and completion for just about
everything (such as command options and manpages). For example, if I have the
following files in my home directory:
README_Solaris8.txt
README_Solaris9.txt
REALLY_LONG_FILE.txt
and want to read README_SOlaris9.txt. If I type:
cat R<tab><tab>
The shell will beep on the first <tab> and display a list of files beginning
with R. If I then type the letters the two README files have in common,
("EAD") and then <tab> the shell will type out:
$ cat README_Solaris
If I then type 9<tab>, the shell will then complete README_Solaris9.txt.
It's even more useful when trying to find a manpage!
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gull
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response 6 of 35:
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Sep 19 21:14 UTC 2006 |
One feature I remember seeing somewhere, but now can't remember where,
is a directory stack. You could 'push' on the current directory,
change to another one, do some work, then 'pop' back to the original
one. It's a feature I've occasionally wished for when I was deep in a
directory hierarchy.
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