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This manual documents Eshell, a shell-like command interpretor
implemented in Emacs Lisp. It invokes no external processes except for
those requested by the user. It is intended to be a functional
replacement for command shells such as bash, zsh,
rc, or 4dos; since Emacs itself is capable of
handling the sort of tasks accomplished by those tools.
1. What is Eshell? A brief introduction to the Emacs Shell. 2. Installation For users of Emacs 20 and XEmacs. 3. Basic overview The basics of command usage. 4. Commands 5. Arguments 6. Input/Output 7. Process control 8. Extension modules 9. Extras and Goodies 10. Bugs and ideas Known problems, and future ideas. Concept Index Function and Variable Index Key Index
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Eshell is a command shell written in Emacs Lisp. Everything it does, it uses Emacs' facilities to do. This means that Eshell is as portable as Emacs itself. It also means that cooperation with Lisp code is natural and seamless.
What is a command shell? To properly understand the role of a shell, it's necessary to visualize what a computer does for you. Basically, a computer is a tool; in order to use that tool, you must tell it what to do--or give it "commands." These commands take many forms, such as clicking with a mouse on certain parts of the screen. But that is only one form of command input.
By far the most versatile way to express what you want the computer to do is by using an abbreviated language called script. In script, instead of telling the computer, "list my files, please", one writes a standard abbreviated command word---`ls'. Typing `ls' in a command shell is a script way of telling the computer to list your files.(1)
The real flexibility of this approach is apparent only when you realize that there are many, many different ways to list files. Perhaps you want them sorted by name, sorted by date, in reverse order, or grouped by type. Most graphical browsers have simple ways to express this. But what about showing only a few files, or only files that meet a certain criteria? In very complex and specific situations, the request becomes too difficult to express using a mouse or pointing device. It is just these kinds of requests that are easily solved using a command shell.
For example, what if you want to list every Word file on your hard drive, larger than 100 kilobytes in size, and which hasn't been looked at in over six months? That is a good candidate list for deletion, when you go to clean up your hard drive. But have you ever tried asking your computer for such a list? There is no way to do it! At least, not without using a command shell.
The role of a command shell is to give you more control over what your computer does for you. Not everyone needs this amount of control, and it does come at a cost: Learning the necessary script commands to express what you want done. A complicated query, such as the example above, takes time to learn. But if you find yourself using your computer frequently enough, it is more than worthwhile in the long run. Any tool you use often deserves the time spent learning to master it. (2)
As of Emacs 21, Eshell is part of the standard Emacs distribution.
1.1 Contributors to Eshell People who have helped out!
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Contributions to Eshell are welcome. I have limited time to work on this project, but I will gladly add any code you contribute to me to this package.
The following persons have made contributions to Eshell.
Apart from these, a lot of people have sent suggestions, ideas, requests, bug reports and encouragement. Thanks a lot! Without you there would be no new releases of Eshell.
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As mentioned above, Eshell comes preinstalled as of Emacs 21. If you're using Emacs 20.4 or later, or XEmacs 21, you can download the most recent version of Eshell from http://www.gci-net.com/users/j/johnw/Emacs/eshell.tar.gz.
However, if you are using Emacs 21, you may skip this section.
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Here's exactly what to do, with no explanation why:
You should see a version banner displayed.
Confirm that you see a file listing.
Confirm that everything runs correctly. Use M-x eshell-report-bug if not.
(add-to-list 'load-path "<directory where you install Eshell>") (load "eshell-auto") |
Read the manual and enjoy!
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load-path variable. This can be done within Emacs by
typing:
ESC : (add-to-list 'load-path "<path where Eshell resides>") RET ESC : (add-to-list 'load-path "<path where Pcomplete resides>") RET |
ls followed by
RET. You should have already seen a version banner announcing the
version number of this release, followed by a prompt.
eshell-test followed by RET
in the Eshell buffer. It is important that Emacs be left alone while
the tests are running, since extraneous command input may cause some of
the tests to fail (they were never intended to run in the background).
If all of the tests pass, Eshell should work just fine on your system.
If any of the tests fail, please send e-mail to the Eshell maintainer
using the command M-x eshell-report-bug.
lispdir and infodir. The elisp files will be copied to
lispdir, and the info file to infodir.
install-info can
be found on your system.
If you only want to create the compiled elisp files, but don't want to install them, you can type just make instead.
load-path variable. This can be done by adding the following
line to your `.emacs' file:
(add-to-list 'load-path "/usr/local/share/emacs/site-lisp/eshell") |
The actual directory on your system may differ.
(load "eshell-auto") |
eshell-modules-list. This variable selects which Eshell
extension modules you want to use. You will find documentation on each
of those modules in the Info manual.
If you have TeX installed at your site, you can make a typeset manual from `eshell.texi'.
dvi2ps, which does that; there
is also a program which comes together with TeX, dvips, which
you can use. For other printers, use a suitable DVI driver,
e.g., dvilj4 for LaserJet-compatible printers.
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A command shell is a means of entering verbally-formed commands. This is really all that it does, and every feature described in this manual is a means to that end. Therefore, it's important to take firm hold on exactly what a command is, and how it fits in the overall picture of things.
3.1 Commands verbs Commands always begin with a verb. 3.2 Command arguments Some verbs require arguments.
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Commands are expressed using script, a special shorthand language computers can understand with no trouble. Script is an extremely simple language; oddly enough, this is what makes it look so complicated! Whereas normal languages use a variety of embellishments, the form of a script command is always:
verb [arguments] |
The verb expresses what you want your computer to do. There are a fixed number of verbs, although this number is usually quite large. On the author's computer, it reaches almost 1400 in number. But of course, only a handful of these are really necessary.
Sometimes, the verb is all that's written. A verb is always a single
word, usually related to the task it performs. reboot is a
good example. Entering that on GNU/Linux will reboot the
computer--assuming you have sufficient privileges.
Other verbs require more information. These are usually very capable
verbs, and must be told specifically what to do. The extra information
is given in the form of arguments. For example, the
echo verb prints back whatever arguments you type. It
requires these arguments to know what to echo. A proper use of
echo looks like this:
echo This is an example of using echo! |
This script command causes the computer to echo back: "This is an example of using echo!"
Although command verbs are always simple words, like reboot or
echo, arguments may have a wide variety of forms. There are
textual arguments, numerical arguments--even Lisp arguments.
Distinguishing these different types of arguments requires special
typing, for the computer to know exactly what you mean.
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Eshell recognizes several different kinds of command arguments:
Most users need to worry only about the first two. The third, Lisp lists, occur very frequently, but almost always behind the scenes.
Strings are the most common type of argument, and consist of nearly any character. Special characters--those used by Eshell specifically--must be preceded by a backslash (`\'). When in doubt, it is safe to add backslashes anywhere and everywhere.
Here is a more complicated echo example:
echo A\ Multi-word\ Argument\ With\ A\ \$\ dollar |
Beyond this, things get a bit more complicated. While not beyond the reach of someone wishing to learn, it is definitely beyond the scope of this manual to present it all in a simplistic manner. Get comfortable with Eshell as a basic command invocation tool, and learn more about the commands on your system; then come back when it all sits more familiarly on your mind. Have fun!
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4.1 Invocation 4.2 Completion 4.3 Aliases 4.4 History 4.5 Scripts
Essentially, a command shell is all about invoking commands--and everything that entails. So understanding how Eshell invokes commands is the key to comprehending how it all works.
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Unlike regular system shells, Eshell never invokes kernel functions
directly, such as exec(3). Instead, it uses the Lisp functions
available in the Emacs Lisp library. It does this by transforming the
command you specify into a callable Lisp form.(3)
This transformation, from the string of text typed at the command prompt, to the ultimate invocation of either a Lisp function or external command, follows these steps:
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5.1 The Parser 5.2 Variables 5.3 Substitution 5.4 Globbing 5.5 Predicates
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8.1 Writing a module 8.2 Module testing 8.3 Directory handling 8.4 Key rebinding 8.5 Smart scrolling 8.6 Terminal emulation 8.7 Built-in UNIX commands
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If you find a bug or misfeature, don't hesitate to let me know! Send email to johnw@gnu.org. Feature requests should also be sent there. I prefer discussing one thing at a time. If you find several unrelated bugs, please report them separately.
If you have ideas for improvements, or if you have written some extensions to this package, I would like to hear from you. I hope you find this package useful!
10.1 Known problems
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Below is complete list of known problems with Eshell version 2.4.1, which is the version included with Emacs 21.1.
Allow for a bash-compatible syntax, such as:
alias arg=blah
function arg () { blah $* }
|
In fact, piping to a process from a looping construct doesn't work in
general. If I change the call to eshell-copy-handles in
eshell-rewrite-for-command to use eshell-protect, it seems
to work, but the output occurs after the prompt is displayed. The whole
structured command thing is too complicated at present.
bc in eshell-test
On some XEmacs system, the subprocess interaction test fails
inexplicably, although bc works fine at the command prompt.
In XEmacs 21.1.8, the `*Help*' buffer has been renamed such that multiple instances of the `*Help*' buffer can exist.
You press TAB, but no completions appear, even though the directory has matching files. This behavior is rare.
This happens because the grep Lisp function returns immediately,
and then the asynchronous grep process expects to examine the
temporary file, which has since been deleted.
If the text before point reads "./run", and you type C-r r u n, it will repeat the line for every character typed.
Hitting space during a process invocation, such as make, will
cause it to track the bottom of the output; but backspace no longer
scrolls back.
unload-feature Eshell
This happened a few times in Emacs 21, but has been unreproducable since.
sleep-for when killing child processes
Make it so that the Lisp command on the right of the pipe is repeatedly
called with the input strings as arguments. This will require changing
eshell-do-pipeline to handle non-process targets.
See the above entry.
less without arguments on Windows
The result in the Eshell buffer is:
Spawning child process: invalid argument |
Also a new less buffer was created with nothing in it...
(presumably this holds the output of less).
If less.exe is invoked from the Eshell command line, the
expected output is written to the buffer.
Note that this happens on NT-Emacs 20.6.1 on Windows 2000. The term.el
package and the supplied shell both use the cmdproxy program
for running shells.
cp
This is because the tar option --remove-files doesn't do so. Should it be Eshell's job?
standard-output and standard-error
This would be so that if a Lisp function calls print, everything
will happen as it should (albeit slowly).
So that M-DEL acts in a predictable manner, etc.
If a script file, somewhere in the middle, uses `> /dev/null', output from all subsequent commands is swallowed.
Make it similar to the way that `esh-arg.el' is structured. Then add parsing of `$[?\n]'.
/usr/local/src/editors/vim $ vi **/CVS(/)/Root(.)
Invalid regexp: "Unmatched ( or \\("
|
With zsh, the glob above expands to all files named
`Root' in directories named `CVS'.
Perhaps it should interpolate all permutations, and make that the
globbing result, since otherwise hitting return here will result in
"(list of filenames)/bin", which is never valuable. Thus, one could
cat only C backup files by using `ls ${identity *.c}~'.
In that case, having an alias command name glob for
identity would be useful.
umask, implement chmod in Lisp
eshell-expand-file-name
This would use a data table to transform things such as `~+', `...', etc.
It only really needs: to be hooked onto the output filter and the pre-command hook, and to have the input-end and input-start markers. And to know whether the last output group was "successful."
This would include: variables, history, buffer, input, dir stack, etc.
It means that files beginning with a dot should be included in the glob match.
At the moment, this is not supported.
An error should be generated only if eshell-error-if-no-glob is
non-nil.
indent-according-to-mode to occur
eshell-auto-accumulate-list
This is a list of commands for which, if the user presses RET, the text is staged as the next Eshell command, rather than being sent to the current interactive process.
wait doesn't work with process ids at the moment
With smart display active, if RET is held down, after a while it can't keep up anymore and starts outputting blank lines. It only happens if an asynchronous process is involved...
I think the problem is that eshell-send-input is resetting the
input target location, so that if the asynchronous process is not done
by the time the next RET is received, the input processor thinks
that the input is meant for the process; which, when smart display is
enabled, will be the text of the last command line! That is a bug in
itself.
In holding down RET while an asynchronous process is running,
there will be a point in between termination of the process, and the
running of eshell-post-command-hook, which would cause
eshell-send-input to call eshell-copy-old-input, and then
process that text as a command to be run after the process. Perhaps
there should be a way of killing pending input between the death of the
process, and the post-command-hook.
Perhaps toggled by a command, that makes each output block a smart display block.
info alias that can take arguments
So that the user can enter `info chmod', for example.
eshell-browse
It would treat the Eshell buffer as a outline. Collapsing the outline hides all of the output text. Collapsing again would show only the first command run in each directory
This would be expanded by eshell-expand-file-name (see above).
If it's a Lisp function, input redirection implies xargs (in a
way...). If input redirection is added, also update the
file-name-quote-list, and the delimiter list.
With the handling of word specified by an
eshell-special-alist.
eshell-veal-using-options, allow a :complete tag
It would be used to provide completion rules for that command. Then the macro will automagically define the completion function.
eshell-command-on-region, apply redirections to the result
So that `+ > 'blah' would cause the result of the + (using
input from the current region) to be inserting into the symbol
blah.
If an external command is being invoked, the input is sent as standard input, as if a `cat <region> |' had been invoked.
If a Lisp command, or an alias, is invoked, then if the line has no
newline characters, it is divided by whitespace and passed as arguments
to the Lisp function. Otherwise, it is divided at the newline
characters. Thus, invoking + on a series of numbers will add
them; min would display the smallest figure, etc.
eshell-script-mode as a minor mode
It would provide syntax, abbrev, highlighting and indenting support like
emacs-lisp-mode and shell-mode.
bash-style support
This means `!n', `!#', `!:%', and `!:1-' as separate from `!:1*'.
history
fc in Lisp
This would allow for an "output translators", that take a function to modify output with, and a target. Devise a syntax that works well with pipes, and can accomodate multiple functions (i.e., `>'(upcase regexp-quote)' or `>'upcase').
This would be optional, rather than always using the Eshell buffer. This would allow it to be run from the command line (perhaps).
help command
It would call subcommands with `--help', or `-h' or `/?', as appropriate.
stty in Lisp
rc's matching operator, e.g. `~ (list) regexp'
bg and fg as editors of eshell-process-list
Using bg on a process that is already in the background does
nothing. Specifying redirection targets replaces (or adds) to the list
current being used.
jobs print only the processes for the current shell
The syntax table for parsing these should be customizable, such that the user could change it to use rc syntax: `>[2=1]'.
Return them as a list, so that `$_[*]' is all the arguments of the last command.
Make it possible for the user to send char-by-char to the underlying process. Ultimately, I should be able to move away from using term.el altogether, since everything but the ANSI code handling is already part of Eshell. Then, things would work correctly on MS-Windows as well (which doesn't have `/bin/sh', although `term.el' tries to use it).
That is, make (su, bash, telnet,
rlogin, rsh, etc.) be part of
eshell-visual-commands. The only exception is if the shell is
being used to invoke a single command. Then, the behavior should be
based on what that command is.
open
This would search for some way to open its argument (similar to opening a file in the Windows Explorer).
read to be the same as open, only read-only
tail command which uses view-file
It would move point to the end of the buffer, and then turns on
auto-revert mode in that buffer at frequent intervals--and a
head alias which assums an upper limit of
eshell-maximum-line-length characters per line.
dgrep load dired, mark everything, then invoke dired-do-search
This would run Emacs with the appropriate arguments to invoke Eshell only. That way, it could be listed as a login shell.
PS2 string for multi-line input prompts
TERMCAP usage
So that it automatically expands and corrects pathnames. Or make pathname completion for Pcomplete auto-expand `/u/i/std<TAB>' to `/usr/include/std<TAB>'.
pushd stack to disk along with last-dir-ring
eshell/cat which would allow it to sort and uniq
wc in Lisp
Add support for counting sentences, paragraphs, pages, etc.
sort and uniq in Lisp
touch in Lisp
comm in Lisp
epatch command in Lisp
This would call ediff-patch-file, or ediff-patch-buffer,
depending on its argument.
xargs based on command rewriting
That is, `find X | xargs Y' would be indicated using `Y
${find X}'. Maybe eshell-do-pipelines could be changed to
perform this on-thy-fly rewriting.
less that brings up a view-mode buffer
Such that the user can press SPC and DEL, and then q to return to Eshell. It would be equivalent to: `X > #<buffer Y>; view-buffer #<buffer Y>'.
eshell-mode as much a full citizen as shell-mode
Everywhere in Emacs where shell-mode is specially noticed, add
eshell-mode there.
cp target
eshell-command
If the first thing that I do after entering Emacs is to run
eshell-command and invoke ls, and then use M-x
eshell, it doesn't display anything.
Since it keeps the cursor up where the command was invoked.
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This is comparable to viewing the contents of a folder using a graphical display.
For the understandably curious, here is what that command
looks like: But don't let it fool you; once you know what's going on,
it's easier than it looks: ls -lt **/*.doc(Lk+50aM+5).
To see the Lisp form that will be invoked, type: `eshell-parse-command "echo hello"'
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1. What is Eshell?
2. Installation
3. Basic overview
4. Commands
5. Arguments
6. Input/Output
7. Process control
8. Extension modules
9. Extras and Goodies
10. Bugs and ideas
Concept Index
Function and Variable Index
Key Index
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| Button | Name | Go to | From 1.2.3 go to |
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