Eshell

Eshell is a shell-like command interpreter 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.

This manual is for Eshell, the Emacs shell.

Copyright © 1999–2013 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 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”.

(a) The FSF's Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

What is Eshell? A brief introduction to the Emacs Shell.
Command basics The basics of command usage.
Commands
Expansion
Input/Output
Extension modules
Bugs and ideas Known problems, and future ideas.
GNU Free Documentation License The license for this documentation.
Concept Index
Function and Variable Index
Command Index
Key Index

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1 What is Eshell?

Eshell is a command shell written in Emacs Lisp. Everything it does, it uses Emacs's 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

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1.1 Contributors to Eshell

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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2 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.

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2.1 Commands verbs

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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2.2 Command arguments

Eshell recognizes several different kinds of command arguments:

  1. Strings (also called textual arguments)
  2. Numbers (floating point or integer)
  3. Lisp lists
  4. Lisp symbols
  5. Emacs buffers
  6. Emacs process handles

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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3 Commands

In a command shell, everything is done by invoking commands. This chapter covers command invocations in Eshell, including the command history and invoking commands in a script file.

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3.1 Invocation

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 input line into a callable Lisp form.3

The command can be either an Elisp function or an external command. Eshell looks first for an alias with the same name as the command, then a built-in command or a function with the same name; if there is no match, it then tries to execute it as an external command.

The semicolon (;) can be used to separate multiple command invocations on a single line. A command invocation followed by an ampersand (&) will be run in the background. Eshell has no job control, so you can not suspend or background the current process, or bring a background process into the foreground. That said, background processes invoked from Eshell can be controlled the same way as any other background process in Emacs.

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3.2 Arguments

Command arguments are passed to the functions as either strings or numbers, depending on what the parser thinks they look like. If you need to use a function that takes some other data type, you will need to call it in an Elisp expression (which can also be used with expansions). As with other shells, you can escape special characters and spaces with the backslash (\) and the single ('') and double ("") quotes.

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3.3 Built-in commands

Several commands are built-in in Eshell. In order to call the external variant of a built-in command foo, you could call *foo. Usually, this should not be necessary. You can check what will be applied by the which command:

     ~ $ which ls
     eshell/ls is a compiled Lisp function in `em-ls.el'
     ~ $ which *ls
     /bin/ls

If you want to discard a given built-in command, you could declare an alias, Aliases. Example:

     ~ $ which sudo
     eshell/sudo is a compiled Lisp function in `em-unix.el'
     ~ $ alias sudo '*sudo $*'
     ~ $ which sudo
     sudo is an alias, defined as "*sudo $*"

If you would prefer to use the built-in commands instead of the external commands, set eshell-prefer-lisp-functions to t.

Some of the built-in commands have different behaviour from their external counterparts, and some have no external counterpart. Most of these will print a usage message when given the --help option.

addpath
Adds a given path or set of paths to the PATH environment variable, or, with no arguments, prints the current paths in this variable.
alias
Define an alias (see Aliases). This does not add it to the aliases file.
date
Similar to, but slightly different from, the GNU Coreutils date command.
define
Define a varalias. See Variable Aliases.
diff
Use Emacs's internal diff (not to be confused with ediff). See Comparing Files.
grep
agrep
egrep
fgrep
glimpse
The grep commands are compatible with GNU grep, but use Emacs's internal grep instead.
info
Same as the external info command, but uses Emacs's internal Info reader.
jobs
List subprocesses of the Emacs process, if any, using the function list-processes.
kill
Kill processes. Takes a PID or a process object and an optional signal specifier.
listify
Eshell version of list. Allows you to create a list using Eshell syntax, rather than Elisp syntax. For example, ‘listify foo bar’ and ("foo" "bar") both evaluate to ("foo" "bar").
locate
Alias to Emacs's locate function, which simply runs the external locate command and parses the results. See Dired and Find.
make
Run make through compile. See Compilation.
occur
Alias to Emacs's occur. See Other Repeating Search.
printnl
Print the arguments separated by newlines.
cd
This command changes the current working directory. Usually, it is invoked as ‘cd foo’ where foo is the new working directory. But cd knows about a few special arguments:

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

Giving the command ‘cd -’ changes back to the previous working directory (this is the same as ‘cd $-’).

The command ‘cd =’ shows the directory stack. Each line is numbered.

With ‘cd =foo’, Eshell searches the directory stack for a directory matching the regular expression ‘foo’ and changes to that directory.

With ‘cd -42’, you can access the directory stack by number.

su
sudo
Uses TRAMP's su or sudo method to run a command via su or sudo.

3.3.1 Built-in variables

Eshell knows a few built-in variables:

$+
This variable always contains the current working directory.
$-
This variable always contains the previous working directory (the current working directory from before the last cd command).
$_
It refers to the last argument of the last command.
$$
This is the result of the last command. In case of an external command, it is t or nil.
$?
This variable contains the exit code of the last command (0 or 1 for Lisp functions, based on successful completion).

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3.4 Variables

Since Eshell is just an Emacs REPL4, it does not have its own scope, and simply stores variables the same you would in an Elisp program. Eshell provides a command version of setq for convenience.

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3.5 Aliases

Aliases are commands that expand to a longer input line. For example, ll is a common alias for ls -l, and would be defined with the command invocation ‘alias ll ls -l’; with this defined, running ‘ll foo’ in Eshell will actually run ‘ls -l foo’. Aliases defined (or deleted) by the alias command are automatically written to the file named by eshell-aliases-file, which you can also edit directly (although you will have to manually reload it).

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3.6 History

The ‘history’ command shows all commands kept in the history ring as numbered list. If the history ring contains eshell-history-size commands, those numbers change after every command invocation, therefore the ‘history’ command shall be applied before using the expansion mechanism with history numbers.

The n-th entry of the history ring can be applied with the ‘!n’ command. If n is negative, the entry is counted from the end of the history ring.

!foo’ expands to the last command beginning with foo, and ‘!?foo’ to the last command containing foo. The n-th argument of the last command beginning with foo is accessible by !foo:n.

The history ring is loaded from a file at the start of every session, and written back to the file at the end of every session. The file path is specified in eshell-history-file-name. Unlike other shells, such as Bash, Eshell can not be configured to keep a history ring of a different size than that of the history file.

Since the default buffer navigation and searching key-bindings are still present in the Eshell buffer, the commands for history navigation and searching are bound to different keys:

M-r
M-s
History I-search.
M-p
M-n
Previous and next history line. If there is anything on the input line when you run these commands, they will instead jump to the precious or next line that begins with that string.

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3.7 Completion

Eshell uses the pcomplete package for programmable completion, similar to that of other command shells. Argument completion differs depending on the preceding command: for example, possible completions for rmdir are only directories, while rm completions can be directories and files. Eshell provides predefined completions for the built-in functions and some common external commands, and you can define your own for any command.

Eshell completion also works for lisp forms and glob patterns. If the point is on a lisp form, then <TAB> will behave similarly to completion in elisp-mode and lisp-interaction-mode. For glob patterns, If there are few enough possible completions of the patterns, they will be cycled when <TAB> is pressed, otherwise it will be removed from the input line and the possible completions will be listed.

If you want to see the entire list of possible completions when it's below the cycling threshold, press M-?.

3.7.1 pcomplete

Pcomplete, short for programmable completion, is the completion library originally written for Eshell, but usable for command completion5 in other modes.

Completions are defined as functions (with defun) named pcomplete/COMMAND, where COMMAND is the name of the command for which this function provides completions; you can also name the function pcomplete/MAJOR-MODE/COMMAND to define completions for a specific major mode.

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3.8 for loop

Because Eshell commands can not (easily) be combined with lisp forms, Eshell provides a command-oriented for-loop for convenience. The syntax is as follows:

     for VAR in TOKENS { command invocation(s) }

where ‘TOKENS’ is a space-separated sequence of values of VAR for each iteration. This can even be the output of a command if ‘TOKENS’ is replaced with ‘{ command invocation }’.

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3.9 Scripts

You can run Eshell scripts much like scripts for other shells; the main difference is that since Eshell is not a system command, you have to run it from within Emacs. An Eshell script is simply a file containing a sequence of commands, as with almost any other shell script. Scripts are invoked from Eshell with source, or from anywhere in Emacs with eshell-source-file.

If you wish to load a script into your current environment, rather than in a subshell, use the . command.

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4 Expansion

Expansion in a command shell is somewhat like macro expansion in macro parsers (such as cpp and m4), but in a command shell, they are less often used for constants, and usually for using variables and string manipulation.6 For example, $var on a line expands to the value of the variable var when the line is executed. Expansions are usually passed as arguments, but may also be used as commands.7

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4.1 Dollars Expansion

Eshell has different $ expansion syntax from other shells. There are some similarities, but don't let these lull you into a false sense of familiarity.

$var
Expands to the value bound to var. This is the main way to use variables in command invocations.
$#var
Expands to the length of the value bound to var. Raises an error if the value is not a sequence (see Sequences).
$(lisp)
Expands to the result of evaluating the S-expression (lisp). On its own, this is identical to just (lisp), but with the $, it can be used in a string, such as ‘/some/path/$(lisp).txt’.
${command}
Returns the output of command, which can be any valid Eshell command invocation, and may even contain expansions.
$var[i]
Expands to the ith element of the value bound to var. If the value is a string, it will be split at whitespace to make it a list. Again, raises an error if the value is not a sequence.
$var[: i]
As above, but now splitting occurs at the colon character.
$var[: i j]
As above, but instead of returning just a string, it now returns a list of two strings. If the result is being interpolated into a larger string, this list will be flattened into one big string, with each element separated by a space.
$var["\\\\" i]
Separate on backslash characters. Actually, the first argument – if it doesn't have the form of a number, or a plain variable name – can be any regular expression. So to split on numbers, use ‘$var["[0-9]+" 10 20]’.
$var[hello]
Calls assoc on var with "hello", expecting it to be an alist (see Association Lists).
$#var[hello]
Returns the length of the cdr of the element of var who car is equal to "hello".

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4.2 Globbing

Eshell's globbing syntax is very similar to that of Zsh. Users coming from Bash can still use Bash-style globbing, as there are no incompatibilities. Most globbing is pattern-based expansion, but there is also predicate-based expansion. See Filename Generation for full syntax. To customize the syntax and behaviour of globbing in Eshell see the Customize8 groups “eshell-glob” and “eshell-pred”.

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5 Input/Output

Since Eshell does not communicate with a terminal like most command shells, IO is a little different. If you try to run programs from within Eshell that are not line-oriented, such as programs that use ncurses, you will just get garbage output, since the Eshell buffer is not a terminal emulator. Eshell solves this problem by running specified commands in Emacs's terminal emulator; to let Eshell know which commands need to be run in a terminal, add them to the list eshell-visual-commands.

Redirection is mostly the same in Eshell as it is in other command shells. The output redirection operators > and >> as well as pipes are supported, but there is not yet any support for input redirection. Output can also be redirected to Elisp functions, using virtual devices.

eshell-virtual-targets is a list of mappings of virtual device names to functions. Eshell comes with two virtual devices: /dev/kill, which sends the text to the kill ring, and /dev/clip, which sends text to the clipboard.

You can, of course, define your own virtual targets. They are defined by adding a list of the form ("/dev/name" function mode) to eshell-virtual-targets. The first element is the device name; function may be either a lambda or a function name. If mode is nil, then the function is the output function; if it is non-nil, then the function is passed the redirection mode as a symbol–overwrite, append, or insert–and the function is expected to return the output function.

The output function is called once on each line of output until nil is passed, indicating end of output.

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6 Extension modules

Eshell provides a facility for defining extension modules so that they can be disabled and enabled without having to unload and reload them, and to provide a common parent Customize group for the modules.9 An Eshell module is defined the same as any other library but one requirement: the module must define a Customize10 group using eshell-defgroup (in place of defgroup) with eshell-module as the parent group.11 You also need to load the following as shown:

     (eval-when-compile
       (require 'cl)
       (require 'esh-mode)
       (require 'eshell))
     
     (require 'esh-util)

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6.1 Writing a module

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6.2 Module testing

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6.3 Directory handling

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6.4 Key rebinding

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6.5 Smart scrolling

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6.6 Terminal emulation

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7 Bugs and ideas

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!

Below is a complete list of known problems with Eshell version 2.4.2, which is the version included with Emacs 22.

Documentation incomplete
Differentiate between aliases and functions
Allow for a Bash-compatible syntax, such as:
          alias arg=blah
          function arg () { blah $* }

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 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.
Error with bc in eshell-test
On some XEmacs system, the subprocess interaction test fails inexplicably, although bc works fine at the command prompt.
Eshell does not delete *Help* buffers in XEmacs 21.1.8+
In XEmacs 21.1.8, the *Help* buffer has been renamed such that multiple instances of the *Help* buffer can exist.
Pcomplete sometimes gets stuck
You press <TAB>, but no completions appear, even though the directory has matching files. This behavior is rare.
grep python $<rpm -qa>’ doesn't work, but using ‘*grep’ does
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.
Problem with C-r repeating text
If the text before point reads "./run", and you type C-r r u n, it will repeat the line for every character typed.
Backspace doesn't scroll back after continuing (in smart mode)
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.
It's not possible to fully unload-feature Eshell
Menu support was removed, but never put back
Using C-p and C-n with rebind gets into a locked state
This happened a few times in Emacs 21, but has been irreproducible since.
If an interactive process is currently running, M-! doesn't work
Use a timer instead of sleep-for when killing child processes
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 eshell-do-pipeline to handle non-process targets.
Input redirection is not supported
See the above entry.
Problem running 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.

Implement ‘-r’, ‘-n’ and ‘-s’ switches for cp
Make M-5 M-x eshell switch to “*eshell<5>*”, creating if need be
mv dir file.tar’ does not remove directories
This is because the tar option –remove-files doesn't do so. Should it be Eshell's job?
Bind standard-output and standard-error
This would be so that if a Lisp function calls print, everything will happen as it should (albeit slowly).
When an extension module fails to load, ‘cd /’ gives a Lisp error
If a globbing pattern returns one match, should it be a list?
Make sure syntax table is correct in Eshell mode
So that M-DEL acts in a predictable manner, etc.
Allow all Eshell buffers to share the same history and list-dir
There is a problem with script commands that output to /dev/null
If a script file, somewhere in the middle, uses ‘> /dev/null’, output from all subsequent commands is swallowed.
Split up parsing of text after ‘$’ in esh-var.el
Make it similar to the way that esh-arg.el is structured. Then add parsing of ‘$[?\n]’.
After pressing M-RET, redisplay before running the next command
Argument predicates and modifiers should work anywhere in a path
          /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.

Typing ‘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 cat only C backup files by using ‘ls ${identity *.c}~’. In that case, having an alias command name glob for identity would be useful.
Once symbolic mode is supported for umask, implement chmod in Lisp
Create eshell-expand-file-name
This would use a data table to transform things such as ‘~+’, ‘...’, etc.
Abstract em-smart.el into 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.”
Allow for fully persisting the state of Eshell
This would include: variables, history, buffer, input, dir stack, etc.
Implement D as an argument predicate
It means that files beginning with a dot should be included in the glob match.
A comma in a predicate list should mean OR
At the moment, this is not supported.
Error if a glob doesn't expand due to a predicate
An error should be generated only if eshell-error-if-no-glob is non-nil.
(+ RET SPC TAB’ does not cause indent-according-to-mode to occur
Create 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.
Display file and line number if an error occurs in a script
wait doesn't work with process ids at the moment
Enable the direct-to-process input code in em-term.el
Problem with repeating ‘echo ${find /tmp}
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.

Allow for a more aggressive smart display mode
Perhaps toggled by a command, that makes each output block a smart display block.
Create more meta variables
$!
The reason for the failure of the last disk command, or the text of the last Lisp error.
$=
A special associate array, which can take references of the form ‘$=[REGEXP]’. It indexes into the directory ring.

Eshell scripts can't execute in the background
Support zsh's “Parameter Expansion” syntax, i.e., ‘${name:-val}
Write an info alias that can take arguments
So that the user can enter ‘info chmod’, for example.
Create a mode 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
Allow other revisions of a file to be referenced using ‘file{rev}
This would be expanded by eshell-expand-file-name (see above).
Print “You have new mail” when the “Mail” icon is turned on
Implement M-| for Eshell
Implement input redirection
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.
Allow ‘#<word arg>’ as a generic syntax
With the handling of word specified by an eshell-special-alist.
In eshell-eval-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.
For 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.

Write eshell-script-mode as a minor mode
It would provide syntax, abbrev, highlighting and indenting support like emacs-lisp-mode and shell-mode.
In the history mechanism, finish the Bash-style support
This means ‘!n’, ‘!#’, ‘!:%’, and ‘!:1-’ as separate from ‘!:1*’.
Support the -n command line option for history
Implement fc in Lisp
Specifying a frame as a redirection target should imply the currently active window's buffer
Implement ‘>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., ‘>'(upcase regexp-quote)’ or ‘>'upcase’).
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).
Write a help command
It would call subcommands with --help, or -h or /?, as appropriate.
Implement stty in Lisp
Support rc's matching operator, e.g., ‘~ (list) regexp
Implement 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.
Have jobs print only the processes for the current shell
How can Eshell learn if a background process has requested input?
Support ‘2>&1’ and ‘>&’ and ‘2>’ and ‘|&
The syntax table for parsing these should be customizable, such that the user could change it to use rc syntax: ‘>[2=1]’.
Allow ‘$_[-1]’, which would indicate the last element of the array
Make ‘$x[*]’ equal to listing out the full contents of ‘x
Return them as a list, so that ‘$_[*]’ is all the arguments of the last command.
Copy ANSI code handling from term.el into 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 /bin/sh, although term.el tries to use it).
Make the shell spawning commands be visual
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.
Create a smart viewing command named open
This would search for some way to open its argument (similar to opening a file in the Windows Explorer).
Alias read to be the same as open, only read-only
Write a 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 assumes an upper limit of eshell-maximum-line-length characters per line.
Make dgrep load dired, mark everything, then invoke dired-do-search
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.
Use an intangible PS2 string for multi-line input prompts
Auto-detect when a command is visual, by checking TERMCAP usage
The first keypress after M-x watson triggers `eshell-send-input'
Make / electric
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>’.
Write the pushd stack to disk along with last-dir-ring
Add options to eshell/cat which would allow it to sort and uniq
Implement wc in Lisp
Add support for counting sentences, paragraphs, pages, etc.
Once piping is added, implement sort and uniq in Lisp
Implement touch in Lisp
Implement comm in Lisp
Implement an epatch command in Lisp
This would call ediff-patch-file, or ediff-patch-buffer, depending on its argument.
Have an option such that ‘ls -l’ generates a dired buffer
Write a version of 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.
Write an alias for 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>’.
Make eshell-mode as much a full citizen as shell-mode
Everywhere in Emacs where shell-mode is specially noticed, add eshell-mode there.
Permit the umask to be selectively set on a cp target
Problem using M-x eshell after using 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.
M-RET during a long command (using smart display) doesn't work
Since it keeps the cursor up where the command was invoked.

Next: , Previous: Bugs and ideas, Up: Top

Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
     Copyright © 2000, 2001, 2002, 2007, 2008, 2009 Free Software Foundation, Inc.
     http://fsf.org/
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ascii without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

    The “publisher” means any person or entity that distributes copies of the Document to the public.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation's users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document's Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

  12. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

       Copyright (C)  year  your name.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
       Texts.  A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:

         with the Invariant Sections being list their titles, with
         the Front-Cover Texts being list, and with the Back-Cover Texts
         being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

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Concept Index

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Function and Variable Index

Next: , Previous: Function and Variable Index, Up: Top

Command Index

Previous: Command Index, Up: Top

Key Index


Footnotes

[1] This is comparable to viewing the contents of a folder using a graphical display.

[2] 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).

[3] To see the Lisp form that will be invoked, type: ‘eshell-parse-command "echo hello"

[4] Read-Eval-Print Loop

[5] Command completion as opposed to code completion, which is a beyond the scope of pcomplete.

[6] Eshell has no string-manipulation expansions because the Elisp library already provides many functions for this.

[7] E.g., entering just ‘$var’ at the prompt is equivalent to entering the value of var at the prompt.

[8] See Easy Customization.

[9] ERC provides a similar module facility.

[10] See Customization.

[11] If the module has no user-customizable options, then there is no need to define it as an Eshell module.