emacs/man/eshell.texi

\input texinfo  @c -*-texinfo-*-
@c "@(#)$Name:  $:$Id: eshell.texi,v 1.16 2002/10/02 23:24:31 karl Exp $"
@c %**start of header
@setfilename ../info/eshell
@settitle Eshell: The Emacs Shell
@synindex vr fn
@c %**end of header

@copying
This manual is for Eshell, the Emacs shell.

Copyright @copyright{} 1999, 2000, 2001, 2002 Free Software Foundation, Inc.

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with the Front-Cover texts being ``A GNU
Manual'', and with the Back-Cover Texts as in (a) below.  A copy of the
license is included in the section entitled ``GNU Free Documentation
License'' in the Emacs manual.

(a) The FSF's Back-Cover Text is: ``You have freedom to copy and modify
this GNU Manual, like GNU software.  Copies published by the Free
Software Foundation raise funds for GNU development.''

This document is part of a collection distributed under the GNU Free
Documentation License.  If you want to distribute this document
separately from the collection, you can do so by adding a copy of the
license to the document, as described in section 6 of the license.
@end quotation
@end copying

@dircategory Emacs
@direntry
* Eshell: (eshell).     A command shell implemented in Emacs Lisp.
@end direntry

@setchapternewpage on

@titlepage
@sp 4
@c The title is printed in a large font.
@center @titlefont{User's Guide}
@sp
@center @titlefont{to}
@sp
@center @titlefont{Eshell: The Emacs Shell}
@ignore
@sp 2
@center release 2.4
@c -release-
@end ignore
@sp 3
@center John Wiegley
@c -date-

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents

@c ================================================================
@c                   The real text starts here
@c ================================================================

@ifnottex
@node Top, What is Eshell?, (dir), (dir)
@top Eshell

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 @command{bash}, @command{zsh},
@command{rc}, or @command{4dos}; since Emacs itself is capable of
handling the sort of tasks accomplished by those tools.
@c This manual is updated to release 2.4 of Eshell.
@end ifnottex

@menu
* What is Eshell?::             A brief introduction to the Emacs Shell.
* Installation::                For users of Emacs 20 and XEmacs.
* Command basics::              The basics of command usage.     
* Commands::                    
* Arguments::                   
* Input/Output::                
* Process control::             
* Extension modules::           
* Extras and Goodies::          
* Bugs and ideas::              Known problems, and future ideas.
* Concept Index::               
* Function and Variable Index::  
* Key Index::                   
@end menu

@node What is Eshell?
@chapter What is Eshell?
@cindex what is Eshell?
@cindex Eshell, what it is

Eshell is a @dfn{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 @dfn{script}.  In
script, instead of telling the computer, ``list my files, please'',
one writes a standard abbreviated command word---@samp{ls}.  Typing
@samp{ls} in a command shell is a script way of telling the computer
to list your files.@footnote{This is comparable to viewing the
contents of a folder using a graphical display.}

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.
@footnote{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: @code{ls -lt **/*.doc(Lk+50aM+5)}.}

As of Emacs 21, Eshell is part of the standard Emacs distribution.

@menu
* Contributors to Eshell::      People who have helped out!
@end menu

@node Contributors to Eshell
@section Contributors to Eshell
@cindex contributors
@cindex authors

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.

@itemize @bullet
@item
Eli Zaretskii made it possible for Eshell to run without requiring
asynchronous subprocess support.  This is important for MS-DOS, which
does not have such support.@refill

@item
Miles Bader contributed many fixes during the port to Emacs 21.@refill

@item
Stefan Monnier fixed the things which bothered him, which of course made
things better for all.@refill

@item
Gerd Moellmann also helped to contribute bug fixes during the initial
integration with Emacs 21.@refill

@item
Alex Schroeder contributed code for interactively querying the user
before overwriting files.@refill

@item
Sudish Joseph helped with some XEmacs compatibility issues.@refill
@end itemize

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.

@node Installation
@chapter Installation
@cindex installation

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
@url{http://www.gci-net.com/users/j/johnw/Emacs/packages/eshell.tar.gz}.

However, if you are using Emacs 21, you may skip this section.

@section Short Form

Here's exactly what to do, with no explanation why:

@enumerate
@item
@samp{M-x load-file RET eshell-auto.el RET}.

@item
@samp{ESC : (add-to-list 'load-path "<path where Eshell resides>") RET}.

@item
@samp{ESC : (add-to-list 'load-path "<path where Pcomplete resides>") RET}.

@item
@samp{M-x eshell RET}.

You should see a version banner displayed.

@item
@samp{ls RET}.

Confirm that you see a file listing.

@item
@samp{eshell-test RET}.

Confirm that everything runs correctly.  Use @kbd{M-x eshell-report-bug} if
not.

@item
@samp{cd $@{dirname (locate-library "eshell-auto")@} RET}.

@item
@samp{find-file Makefile RET}.

@item
Edit the Makefile to reflect your site.

@item
@samp{M-x eshell RET}.

@item
@samp{make install RET}.

@item
@samp{find-file $user-init-file RET}.

@item
Add the following lines to your @file{.emacs} file:

@example
(add-to-list 'load-path "<directory where you install Eshell>")
(load "eshell-auto")
@end example

@item
@samp{M-x eshell RET}.

@item
@samp{customize-option #'eshell-modules-list RET}.

@item
Select the extension modules you prefer.

@item
Restart Emacs!

@item
@samp{M-x info RET m Eshell RET}.

Read the manual and enjoy!
@end enumerate

@section Long Form

@enumerate
@item
Before building and installing Eshell, it is important to test that it
will work properly on your system.  To do this, first load the file
@file{eshell-auto}, which will define certain autoloads required to run
Eshell.  This can be done using the command @kbd{M-x load-file}, and
then selecting the file @file{eshell-auto.el}.

@item
In order for Emacs to find Eshell's files, the Eshell directory must be
added to the @code{load-path} variable.  This can be done within Emacs by
typing:

@example
ESC : (add-to-list 'load-path "<path where Eshell resides>") RET
ESC : (add-to-list 'load-path "<path where Pcomplete resides>") RET
@end example

@item
Start Eshell from the distributed sources, using default settings, by
typing @kbd{M-x eshell}.

@item
Verify that Eshell is functional by typing @command{ls} followed by
@key{RET}.  You should have already seen a version banner announcing the
version number of this release, followed by a prompt.

@item
Run the test suite by typing @command{eshell-test} followed by @key{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 @kbd{M-x eshell-report-bug}.

@item
Edit the file @file{Makefile} in the directory containing the Eshell
sources to reflect the location of certain Emacs directories at your
site.  The only things you really have to change are the definitions of
@code{lispdir} and @code{infodir}.  The elisp files will be copied to
@code{lispdir}, and the info file to @code{infodir}.

@item
Type @kbd{make install} in the directory containing the Eshell sources.
This will byte-compile all of the @file{*.el} files and copy both the
source and compiled versions to the directories specified in the
previous step.  It will also copy the info file, and add a corresponding
entry to your @file{dir} file----if the program @code{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 @kbd{make} instead.

@item
Add the directory into which Eshell was installed to your
@code{load-path} variable.  This can be done by adding the following
line to your @file{.emacs} file:

@example
(add-to-list 'load-path "/usr/local/share/emacs/site-lisp/eshell")
@end example

The actual directory on your system may differ.

@item
To install Eshell privately, edit your @file{.emacs} file; to install
Eshell site-wide, edit the file @file{site-start.el} in your
@file{site-lisp} directory (usually
@file{/usr/local/share/emacs/site-lisp} or something similar).  In
either case enter the following line into the appropriate file:

@example
(load "eshell-auto")
@end example

@item
Restart Emacs.  After restarting, customize the variable
@code{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.
@end enumerate

@cindex documentation, printed version
@cindex printed version of documentation
If you have @TeX{} installed at your site, you can make a typeset manual
from @file{eshell.texi}.

@enumerate
@item
Run @TeX{} by typing @kbd{texi2dvi eshell.texi}.  (With Emacs 21.1 or
later, typing @kbd{make eshell.dvi} in the @file{man/} subdirectory of
the Emacs source distribution will do that.)

@item
Convert the resulting device independent file @file{eshell.dvi} to a
form which your printer can output and print it.  If you have a
postscript printer, there is a program, @code{dvi2ps}, which does that; there
is also a program which comes together with @TeX{}, @code{dvips}, which
you can use.  For other printers, use a suitable DVI driver,
e.g., @code{dvilj4} for LaserJet-compatible printers.
@end enumerate

@node Command basics
@chapter Basic overview

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.

@menu
* Commands verbs::              Commands always begin with a verb.
* Command arguments::           Some verbs require arguments.
@end menu

@node Commands verbs
@section Commands verbs

Commands are expressed using @dfn{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:

@example
@var{verb} [@var{arguments}]
@end example

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.  @command{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 @dfn{arguments}.  For example, the
@command{echo} verb prints back whatever arguments you type.  It
requires these arguments to know what to echo.  A proper use of
@command{echo} looks like this:

@example
echo This is an example of using echo!
@end example

This script command causes the computer to echo back: ``This is an
example of using echo!''

Although command verbs are always simple words, like @command{reboot} or
@command{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.

@node Command arguments
@section Command arguments

Eshell recognizes several different kinds of command arguments:

@enumerate
@item Strings (also called textual arguments)
@item Numbers (floating point or integer)
@item Lisp lists
@item Lisp symbols
@item Emacs buffers
@item Emacs process handles
@end enumerate

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 (@samp{\}).  When in doubt, it
is safe to add backslashes anywhere and everywhere.

Here is a more complicated @command{echo} example:

@example
echo A\ Multi-word\ Argument\ With\ A\ \$\ dollar
@end example

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!

@node Commands
@chapter Commands

@menu
* Invocation::                  
* Completion::                  
* Aliases::                     
* History::                     
* Scripts::                     
* Built-ins::
@end menu

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.

@node Invocation
@section Invocation

Unlike regular system shells, Eshell never invokes kernel functions
directly, such as @code{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.@footnote{To see the Lisp
form that will be invoked, type: @samp{eshell-parse-command "echo
hello"}}

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:

@enumerate
@item Parse the command string into separate arguments.
@item 
@end enumerate

@node Completion
@section Completion

@node Aliases
@section Aliases

@node History
@section History

Eshell knows a few built-in variables:

@table @code

@item $+
@vindex $+
This variable always contains the current working directory.

@item $-
@vindex $-
This variable always contains the previous working directory (the
current working directory from before the last @code{cd} command).

@end table

@node Scripts
@section Scripts


@node Built-ins
@section Built-in commands

Here is a list of built-in commands that Eshell knows about:

@table @code

@item cd
@findex cd
This command changes the current working directory.  Usually, it is
invoked as @samp{cd foo} where @file{foo} is the new working
directory.  But @code{cd} knows about a few special arguments:

When it receives no argument at all, it changes to the home directory.

Giving the command @samp{cd -} changes back to the previous working
directory (this is the same as @samp{cd $-}).

The command @samp{cd =} shows the directory stack.  Each line is
numbered.

With @samp{cd =foo}, Eshell searches the directory stack for a
directory matching the regular expression @samp{foo} and changes to
that directory.

With @samp{cd -42}, you can access the directory stack by number.

@end table


@node Arguments
@chapter Arguments

@menu
* The Parser::                  
* Variables::                   
* Substitution::                
* Globbing::                    
* Predicates::                  
@end menu

@node The Parser
@section The Parser

@node Variables
@section Variables

@node Substitution
@section Substitution

@node Globbing
@section Globbing

@node Predicates
@section Predicates


@node Input/Output
@chapter Input/Output

@node Process control
@chapter Process control


@node Extension modules
@chapter Extension modules

@menu
* Writing a module::            
* Module testing::              
* Directory handling::          
* Key rebinding::               
* Smart scrolling::             
* Terminal emulation::          
* Built-in UNIX commands::      
@end menu

@node Writing a module
@section Writing a module

@node Module testing
@section Module testing

@node Directory handling
@section Directory handling

@node Key rebinding
@section Key rebinding

@node Smart scrolling
@section Smart scrolling

@node Terminal emulation
@section Terminal emulation

@node Built-in UNIX commands
@section Built-in UNIX commands


@node Extras and Goodies
@chapter Extras and Goodies

@node Bugs and ideas
@chapter Bugs and ideas
@cindex reporting bugs and ideas
@cindex bugs, how to report them
@cindex author, how to reach
@cindex email to the author
@cindex FAQ
@cindex problems, list of common

If you find a bug or misfeature, don't hesitate to let me know!  Send
email to @email{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!

@menu
* Known problems::              
@end menu

@node Known problems
@section Known problems
@cindex known bugs
@cindex bugs, known

Below is complete list of known problems with Eshell version 2.4.1,
which is the version included with Emacs 21.1.

@table @asis
@item Differentiate between aliases and functions

Allow for a bash-compatible syntax, such as:

@example
alias arg=blah
function arg () @{ blah $* @}
@end example

@item @samp{for i in 1 2 3 @{ grep -q a b && *echo has it @} | wc -l} outputs result after prompt

In fact, piping to a process from a looping construct doesn't work in
general.  If I change the call to @code{eshell-copy-handles} in
@code{eshell-rewrite-for-command} to use @code{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.

@item Error with @command{bc} in @code{eshell-test}

On some XEmacs system, the subprocess interaction test fails
inexplicably, although @command{bc} works fine at the command prompt.

@item Eshell does not delete @file{*Help*} buffers in XEmacs 21.1.8+

In XEmacs 21.1.8, the @file{*Help*} buffer has been renamed such that
multiple instances of the @file{*Help*} buffer can exist.

@item Pcomplete sometimes gets stuck

You press @key{TAB}, but no completions appear, even though the
directory has matching files.  This behavior is rare.

@item @samp{grep python $<rpm -qa>} doesn't work, but using @samp{*grep} does

This happens because the @code{grep} Lisp function returns immediately,
and then the asynchronous @command{grep} process expects to examine the
temporary file, which has since been deleted.

@item Problem with C-r repeating text

If the text @emph{before point} reads "./run", and you type @kbd{C-r r u
n}, it will repeat the line for every character typed.

@item Backspace doesn't scroll back after continuing (in smart mode)

Hitting space during a process invocation, such as @command{make}, will
cause it to track the bottom of the output; but backspace no longer
scrolls back.

@item It's not possible to fully @code{unload-feature} Eshell

@item Menu support was removed, but never put back

@item Using C-p and C-n with rebind gets into a locked state

This happened a few times in Emacs 21, but has been unreproducible
since.

@item If an interactive process is currently running, @kbd{M-!} doesn't work

@item Use a timer instead of @code{sleep-for} when killing child processes

@item Piping to a Lisp function is not supported

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
@code{eshell-do-pipeline} to handle non-process targets.

@item Input redirection is not supported

See the above entry.

@item Problem running @command{less} without arguments on Windows

The result in the Eshell buffer is:

@example
Spawning child process: invalid argument
@end example

Also a new @command{less} buffer was created with nothing in it@dots{}
(presumably this holds the output of @command{less}).

If @command{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 @command{cmdproxy} program
for running shells.

@item Implement @samp{-r}, @samp{-n} and @samp{-s} switches for @command{cp}

@item Make @kbd{M-5 M-x eshell} switch to ``*eshell<5>*'', creating if need be

@item @samp{mv @var{dir} @var{file}.tar} does not remove directories

This is because the tar option --remove-files doesn't do so.  Should it
be Eshell's job?

@item Bind @code{standard-output} and @code{standard-error}

This would be so that if a Lisp function calls @code{print}, everything
will happen as it should (albeit slowly).

@item When an extension module fails to load, @samp{cd /} gives a Lisp error

@item If a globbing pattern returns one match, should it be a list?

@item Make sure syntax table is correct in Eshell mode

So that @kbd{M-DEL} acts in a predictable manner, etc.

@item Allow all Eshell buffers to share the same history and list-dir

@item There is a problem with script commands that output to @file{/dev/null}

If a script file, somewhere in the middle, uses @samp{> /dev/null},
output from all subsequent commands is swallowed.

@item Split up parsing of text after @samp{$} in @file{esh-var.el}

Make it similar to the way that @file{esh-arg.el} is structured.
Then add parsing of @samp{$[?\n]}.

@item After pressing @kbd{M-RET}, redisplay before running the next command

@item Argument predicates and modifiers should work anywhere in a path

@example
/usr/local/src/editors/vim $ vi **/CVS(/)/Root(.)
Invalid regexp: "Unmatched ( or \\("
@end example

With @command{zsh}, the glob above expands to all files named
@file{Root} in directories named @file{CVS}.

@item Typing @samp{echo $@{locate locate@}/bin<TAB>} results in a Lisp error

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
@command{cat} only C backup files by using @samp{ls $@{identity *.c@}~}.
In that case, having an alias command name @command{glob} for
@command{identity} would be useful.

@item Once symbolic mode is supported for @command{umask}, implement @command{chmod} in Lisp

@item Create @code{eshell-expand-file-name}

This would use a data table to transform things such as @samp{~+},
@samp{...}, etc.

@item Abstract @file{em-smart.el} into @file{smart-scroll.el}

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.''

@item Allow for fully persisting the state of Eshell

This would include: variables, history, buffer, input, dir stack, etc.

@item Implement D as an argument predicate

It means that files beginning with a dot should be included in the
glob match.

@item A comma in a predicate list should mean OR

At the moment, this is not supported.

@item Error if a glob doesn't expand due to a predicate

An error should be generated only if @code{eshell-error-if-no-glob} is
non-nil.

@item @samp{(+ RET SPC TAB} does not cause @code{indent-according-to-mode} to occur

@item Create @code{eshell-auto-accumulate-list}

This is a list of commands for which, if the user presses @kbd{RET}, the
text is staged as the next Eshell command, rather than being sent to the
current interactive process.

@item Display file and line number if an error occurs in a script

@item @command{wait} doesn't work with process ids at the moment

@item Enable the direct-to-process input code in @file{em-term.el}

@item Problem with repeating @samp{echo $@{find /tmp@}}

With smart display active, if @kbd{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@dots{}

I think the problem is that @code{eshell-send-input} is resetting the
input target location, so that if the asynchronous process is not done
by the time the next @kbd{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 @kbd{RET} while an asynchronous process is running,
there will be a point in between termination of the process, and the
running of @code{eshell-post-command-hook}, which would cause
@code{eshell-send-input} to call @code{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 @code{post-command-hook}.

@item Allow for a more aggressive smart display mode

Perhaps toggled by a command, that makes each output block a smart
display block.

@item Create more meta variables

@table @samp
@item $!
The reason for the failure of the last disk command, or the text of the
last Lisp error.

@item $=
A special associate array, which can take references of the form
@samp{$=[REGEXP]}.  It indexes into the directory ring.
@end table

@item Eshell scripts can't execute in the background

@item Support zsh's ``Parameter Expansion'' syntax, i.e. @samp{$@{@var{name}:-@var{val}@}}

@item Write an @command{info} alias that can take arguments

So that the user can enter @samp{info chmod}, for example.

@item Create a mode @code{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

@item Allow other revisions of a file to be referenced using @samp{file@{rev@}}

This would be expanded by @code{eshell-expand-file-name} (see above).

@item Print ``You have new mail'' when the ``Mail'' icon is turned on

@item Implement @kbd{M-|} for Eshell

@item Implement input redirection

If it's a Lisp function, input redirection implies @command{xargs} (in a
way@dots{}).  If input redirection is added, also update the
@code{file-name-quote-list}, and the delimiter list.

@item Allow @samp{#<@var{word} @var{arg}>} as a generic syntax

With the handling of @emph{word} specified by an
@code{eshell-special-alist}.

@item In @code{eshell-veal-using-options}, allow a @code{:complete} tag

It would be used to provide completion rules for that command.  Then the
macro will automagically define the completion function.

@item For @code{eshell-command-on-region}, apply redirections to the result

So that @samp{+ > 'blah} would cause the result of the @code{+} (using
input from the current region) to be inserting into the symbol
@code{blah}.

If an external command is being invoked, the input is sent as standard
input, as if a @samp{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 @code{+} on a series of numbers will add
them; @code{min} would display the smallest figure, etc.

@item Write @code{eshell-script-mode} as a minor mode

It would provide syntax, abbrev, highlighting and indenting support like
@code{emacs-lisp-mode} and @code{shell-mode}.

@item In the history mechanism, finish the @command{bash}-style support

This means @samp{!n}, @samp{!#}, @samp{!:%}, and @samp{!:1-} as separate
from @samp{!:1*}.

@item Support the -n command line option for @command{history}

@item Implement @command{fc} in Lisp

@item Specifying a frame as a redirection target should imply the currently active window's buffer

@item Implement @samp{>@var{func-or-func-list}}

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 accommodate multiple functions (i.e., @samp{>'(upcase
regexp-quote)} or @samp{>'upcase}).

@item Allow Eshell to read/write to/from standard input and output

This would be optional, rather than always using the Eshell buffer.
This would allow it to be run from the command line (perhaps).

@item Write a @command{help} command

It would call subcommands with @option{--help}, or @option{-h} or
@option{/?}, as appropriate.

@item Implement @command{stty} in Lisp

@item Support @command{rc}'s matching operator, e.g. @samp{~ (@var{list}) @var{regexp}}

@item Implement @command{bg} and @command{fg} as editors of @code{eshell-process-list}

Using @command{bg} on a process that is already in the background does
nothing.  Specifying redirection targets replaces (or adds) to the list
current being used.

@item Have @command{jobs} print only the processes for the current shell

@item How can Eshell learn if a background process has requested input?

@item Support @samp{2>&1} and @samp{>&} and @samp{2>} and @samp{|&}

The syntax table for parsing these should be customizable, such that the
user could change it to use rc syntax: @samp{>[2=1]}.

@item Allow @samp{$_[-1]}, which would indicate the last element of the array

@item Make @samp{$x[*]} equal to listing out the full contents of @samp{x}

Return them as a list, so that @samp{$_[*]} is all the arguments of the
last command.

@item Copy ANSI code handling from @file{term.el} into @file{em-term.el}

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 @file{/bin/sh}, although @file{term.el} tries to use
it).

@item Make the shell spawning commands be visual

That is, make (@command{su}, @command{bash}, @command{telnet},
@command{rlogin}, @command{rsh}, etc.) be part of
@code{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.

@item Create a smart viewing command named @command{open}

This would search for some way to open its argument (similar to opening
a file in the Windows Explorer).

@item Alias @command{read} to be the same as @command{open}, only read-only

@item Write a @command{tail} command which uses @code{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
@command{head} alias which assums an upper limit of
@code{eshell-maximum-line-length} characters per line.

@item Make @command{dgrep} load @code{dired}, mark everything, then invoke @code{dired-do-search}

@item Write mesh.c

This would run Emacs with the appropriate arguments to invoke Eshell
only.  That way, it could be listed as a login shell.

@item Use an intangible @code{PS2} string for multi-line input prompts

@item Auto-detect when a command is visual, by checking @code{TERMCAP} usage

@item The first keypress after @kbd{M-x watson} triggers `eshell-send-input'

@item Make @kbd{/} electric

So that it automatically expands and corrects pathnames.  Or make
pathname completion for Pcomplete auto-expand @samp{/u/i/std<TAB>} to
@samp{/usr/include/std<TAB>}.

@item Write the @command{pushd} stack to disk along with @code{last-dir-ring}

@item Add options to @code{eshell/cat} which would allow it to sort and uniq

@item Implement @command{wc} in Lisp

Add support for counting sentences, paragraphs, pages, etc.

@item Once piping is added, implement @command{sort} and @command{uniq} in Lisp

@item Implement @command{touch} in Lisp

@item Implement @command{comm} in Lisp

@item Implement an @command{epatch} command in Lisp

This would call @code{ediff-patch-file}, or @code{ediff-patch-buffer},
depending on its argument.

@item Have an option such that @samp{ls -l} generates a dired buffer

@item Write a version of @command{xargs} based on command rewriting

That is, @samp{find X | xargs Y} would be indicated using @samp{Y
$@{find X@}}.  Maybe @code{eshell-do-pipelines} could be changed to
perform this on-thy-fly rewriting.

@item Write an alias for @command{less} that brings up a @code{view-mode} buffer

Such that the user can press @key{SPC} and @key{DEL}, and then @key{q}
to return to Eshell.  It would be equivalent to: 
@samp{X > #<buffer Y>; view-buffer #<buffer Y>}.

@item Make @code{eshell-mode} as much a full citizen as @code{shell-mode}

Everywhere in Emacs where @code{shell-mode} is specially noticed, add
@code{eshell-mode} there.

@item Permit the umask to be selectively set on a @command{cp} target

@item Problem using @kbd{M-x eshell} after using @code{eshell-command}

If the first thing that I do after entering Emacs is to run
@code{eshell-command} and invoke @command{ls}, and then use @kbd{M-x
eshell}, it doesn't display anything.

@item @kbd{M-RET} during a long command (using smart display) doesn't work

Since it keeps the cursor up where the command was invoked.

@end table

@node Concept Index
@unnumbered Concept Index

@printindex cp

@node Function and Variable Index
@unnumbered Function and Variable Index

@printindex fn

@node Key Index
@unnumbered Key Index

@printindex ky
@bye