     [file docstyle.texi not included]

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 an alternative to the IELM (see Lisp Interaction (The Emacs Editor)) REPL (Short for ``Read-Eval-Print Loop''.) for Emacs and with an interface similar to command shells such as bash, zsh, rc, or 4dos.

This manual is for Eshell, the Emacs shell.

Copyright © 1999--2024 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.''

Introduction
************

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. (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. (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+100aM+6).)

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.

  * John Wiegley is the original author of Eshell.

  * 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.

  * Miles Bader contributed many fixes during the port to Emacs 21.

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

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

  * Alex Schroeder contributed code for interactively querying the user before overwriting files.

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.

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.

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. (To see the Lisp form that will be invoked, type this as the Eshell prompt: eshell-parse-command 'echo hello')

Invocation
==========

Eshell is both a command shell and an Emacs Lisp REPL.  As a result, you can invoke commands in two different ways: in command form or in Lisp form.

You can use the semicolon (;) to separate multiple command invocations on a single line, executing each in turn.  You can also separate commands with && or ||. When using &&, Eshell will execute the second command only if the first succeeds (i.e. has an exit status of 0); with ||, Eshell will execute the second command only if the first fails.

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.

Command form
------------

Command form looks much the same as in other shells.  A command consists of arguments separated by spaces; the first argument is the command to run, with any subsequent arguments being passed to that command.

     ~ $ echo hello
     hello

The command can be either an Elisp function or an external command. Eshell looks for the command in the following order:

 1. As a command alias (see Aliases)

 2. As a built-in command (see Built-ins)

 3. As an external program

 4. As an ordinary Lisp function

If you would prefer to use ordinary Lisp functions over external programs, set the option eshell-prefer-lisp-functions to t.  This will swap the lookup order of the last two items.  You can also force Eshell to look for a command as an external program by prefixing its name with *, like *COMMAND (see Built-ins).

You can also group command forms together into a subcommand with curly braces ({}).  This lets you use the output of a subcommand as an argument to another command, or within control flow statements (see Control Flow).

     ~ $ echo {echo hello; echo there}
     hellothere

Lisp form
---------

Lisp form looks like ordinary Emacs Lisp code, because that's what it is.  As a result, you can use any syntax normally available to an Emacs Lisp program (see The Emacs Lisp Reference Manual).

     ~ $ (format "hello, %s" user-login-name)
     hello, user

In addition, you can combine command forms and Lisp forms together into single statements, letting you use whatever form is the most convenient for expressing your intentions.

     ~ $ ls *.patch > (format-time-string "%F.log")

This command writes a list of all files matching the glob pattern *.patch (see Globbing) to a file named CURRENT-DATE.log (see Redirection).

Arguments
=========

Ordinarily, Eshell parses arguments in command form as either strings or numbers, depending on what the parser thinks they look like.  To specify an argument of some other data type, you can use a Lisp form (see Invocation):

     ~ $ echo (list 1 2 3)
     (1 2 3)

Additionally, many built-in Eshell commands (see Built-ins) will flatten the arguments they receive, so passing a list as an argument will ``spread'' the elements into multiple arguments:

     ~ $ printnl (list 1 2) 3
     1
     2
     3

Quoting and escaping
--------------------

As with other shells, you can escape special characters and spaces by prefixing the character with a backslash (\), or by surrounding the string with apostrophes ('') or double quotes (""). This is needed especially for file names with special characters like pipe (|) or square brackets ([ or ]), which could be part of remote file names.

When you escape a character with \ outside of any quotes, the result is the literal character immediately following it.  For example, \$10 means the literal string $10.

Inside of double quotes, most characters have no special meaning. However, \, ", and $ are still special; to escape them, use backslash as above.  Thus, if the value of the variable ANSWER is 42, then "The answer is: \"$ANSWER\"" returns the string The answer is: "42".  However, when escaping characters with no special meaning, the result is the full \C sequence.  For example, "foo\bar" means the literal string foo\bar.

Additionally, when escaping a newline, the whole escape sequence is removed by the parser.  This lets you continue commands across multiple lines:

     ~ $ echo "foo\
     bar"
     foobar

Inside apostrophes, escaping works differently.  All characters between the apostrophes have their literal meaning except ', which ends the quoted string.  To insert a literal apostrophe, you can use '', so 'It''s me' means the literal string It's me.

When using expansions (see Expansion) in an Eshell command, the result may potentially be of any data type.  To ensure that the result is always a string, the expansion can be surrounded by double quotes.

Special argument types
----------------------

In addition to strings and numbers, Eshell supports a number of special argument types.  These let you refer to various other Emacs Lisp data types, such as lists or buffers.

#'LISP-FORM
     This refers to the quoted Emacs Lisp form LISP-FORM.  Though this looks similar to the ``sharp quote'' syntax for functions (see Special Read Syntax (The Emacs Lisp Reference Manual)), it instead corresponds to quote and can be used for any quoted form. (Eshell would interpret a bare apostrophe (') as the start of a single-quoted string.)

`LISP-FORM
     This refers to the backquoted Emacs Lisp form LISP-FORM (see Backquote (The Emacs Lisp Reference Manual)).  As in Emacs Lisp, you can use , and ,@ to refer to non-constant values.

#<buffer NAME>
#<NAME>
     Return the buffer named NAME.  This is equivalent to $(get-buffer-create "NAME") (see Creating Buffers (The Emacs Lisp Reference Manual)).

#<process NAME>
     Return the process named NAME.  This is equivalent to $(get-process "NAME") (see Process Information (The Emacs Lisp Reference Manual)).

Built-in commands
=================

Eshell provides a number of built-in commands, many of them implementing common command-line utilities, but enhanced for Eshell. (These built-in commands are just ordinary Lisp functions whose names begin with 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 (see Aliases).  Example:

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

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

In some cases, a built-in command's behavior can be configured via user settings, some of which are mentioned below.  For example, certain commands have two user settings to allow them to overwrite files without warning and to ensure that they always prompt before overwriting files.  If both settings are non-nil, the commands always prompt.  If both settings are nil (the default), the commands signal an error.

Several commands observe the value of eshell-default-target-is-dot.  If non-nil, then the default target for the commands cp, mv, and ln is the current directory.

A few commands are wrappers for more niche Emacs features, and can be loaded as part of the eshell-xtra module.  See Extension modules.

.
     Source an Eshell file in the current environment.  This is not to be confused with the command source, which sources a file in a subshell environment.

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 adds it to the aliases file.

basename
     Return a file name without its directory.

cat
     Concatenate file contents into standard output.  If in a pipeline, or if the file is not a regular file, directory, or symlink, then this command reverts to the system's definition of cat.

cd
     This command changes the current working directory.  Usually, it is invoked as cd DIR where DIR 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 ring.  Each line is numbered.

       - With cd =foo, Eshell searches the directory ring for a directory matching the regular expression foo, and changes to that directory.

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

       - If eshell-cd-shows-directory is non-nil, cd will report the directory it changes to.  If eshell-list-files-after-cd is non-nil, then ls is called with any remaining arguments after changing directories.

clear
     Scrolls the contents of the Eshell window out of sight, leaving a blank window.  If provided with an optional non-nil argument, the scrollback contents are cleared instead.

clear-scrollback
     Clear the scrollback contents of the Eshell window.  Unlike the command clear, this command deletes content in the Eshell buffer.

cp
     Copy a file to a new location or copy multiple files to the same directory.

     If eshell-cp-overwrite-files is non-nil, then cp will overwrite files without warning.  If eshell-cp-interactive-query is non-nil, then cp will ask before overwriting anything.

date
     Print the current local time as a human-readable string.  This command is similar to, but slightly different from, the GNU Coreutils date command.

diff
     Compare files using Emacs's internal diff (not to be confused with ediff).  See Comparing Files (The GNU Emacs Manual).

     If eshell-plain-diff-behavior is non-nil, then this command does not use Emacs's internal diff.  This is the same as using alias diff '*diff $*'.

dirname
     Return the directory component of a file name.

dirs
     Prints the directory stack.  Directories can be added or removed from the stack using the commands pushd and popd, respectively.

du
     Summarize disk usage for each file.

echo
     Echoes its input.  By default, this prints in a Lisp-friendly fashion (so that the value is useful to a Lisp command using the result of echo as an argument).  If a single argument is passed, echo prints that; if multiple arguments are passed, it prints a list of all the arguments; otherwise, it prints the empty string.

     If eshell-plain-echo-behavior is non-nil, echo will try to behave more like a plain shell's echo, printing each argument as a string, separated by a space.

env
     Prints the current environment variables.  Unlike in Bash, this command does not yet support running commands with a modified environment.

eshell-debug
     Toggle debugging information for Eshell itself.  You can pass this command the argument errors to enable/disable Eshell trapping errors when evaluating commands, or the argument commands to show/hide command execution progress in the buffer *eshell last cmd*.

exit
     Exit Eshell and save the history.  By default, this command kills the Eshell buffer, but if eshell-kill-on-exit is nil, then the buffer is merely buried instead.

export
     Set environment variables using input like Bash's export, as in export VAR1=VAL1 VAR2=VAL2 ....

grep
agrep
egrep
fgrep
glimpse
     The grep commands are compatible with GNU grep, but use Emacs's internal grep instead. See Grep Searching (The GNU Emacs Manual).

     If eshell-plain-grep-behavior is non-nil, then these commands do not use Emacs's internal grep.  This is the same as using alias grep '*grep $*', though this setting applies to all of the built-in commands for which you would need to create a separate alias.

history
     Prints Eshell's input history.  With a numeric argument N, this command prints the N most recent items in the history.

info
     Browse the available Info documentation.  This command is the same as the external info command, but uses Emacs's internal Info reader. See Misc Help (The GNU Emacs Manual).

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 which can either be a number or a signal name.

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").

ln
     Create links to files.

     If eshell-ln-overwrite-files is non-nil, ln will overwrite files without warning.  If eshell-ln-interactive-query is non-nil, then ln will ask before overwriting files.

locate
     Alias to Emacs's locate function, which simply runs the external locate command and parses the results. See Dired and Find (The GNU Emacs Manual).

     If eshell-plain-locate-behavior is non-nil, then Emacs's internal locate is not used.  This is the same as using alias locate '*locate $*'.

ls
     Lists the contents of directories.

     If eshell-ls-use-colors is non-nil, the contents of a directory is color-coded according to file type and status.  These colors and the regexps used to identify their corresponding files can be customized via M-x customize-group RET eshell-ls RET.

     The user option eshell-ls-date-format determines how the date is displayed when using the -l option.  The date is produced using the function format-time-string (see Time Parsing (GNU Emacs Lisp Reference Manual)).

     The user option eshell-ls-initial-args contains a list of arguments to include with any call to ls.  For example, you can include the option -h to always use a more human-readable format.

     The user option eshell-ls-default-blocksize determines the default blocksize used when displaying file sizes with the option -s.

make
     Run make through compile when run asynchronously (e.g., make &).  See Compilation (The GNU Emacs Manual).  Otherwise call the external make command.

man
     Display Man pages using the Emacs man command. See Man Page (The GNU Emacs Manual).

mkdir
     Make new directories.

mv
     Move or rename files.

     If eshell-mv-overwrite-files is non-nil, mv will overwrite files without warning.  If eshell-mv-interactive-query is non-nil, mv will prompt before overwriting anything.

occur
     Alias to Emacs's occur. See Other Repeating Search (The GNU Emacs Manual).

popd
     Pop a directory from the directory stack and switch to a another place in the stack.

printnl
     Print the arguments separated by newlines.

pushd
     Push the current directory onto the directory stack, then change to another directory.

     If eshell-pushd-dunique is non-nil, then only unique directories will be added to the stack.  If eshell-pushd-dextract is non-nil, then pushd +N will pop the Nth directory to the top of the stack.

pwd
     Prints the current working directory.

rm
     Removes files, buffers, processes, or Emacs Lisp symbols, depending on the argument.

     If eshell-rm-interactive-query is non-nil, rm will prompt before removing anything.  If eshell-rm-removes-directories is non-nil, then rm can also remove directories.  Otherwise, rmdir is required.

rmdir
     Removes directories if they are empty.

set
     Set variable values, using the function set like a command (see Setting Variables (GNU Emacs Lisp Reference Manual)). A variable name can be a symbol, in which case it refers to a Lisp variable, or a string, referring to an environment variable (see Arguments).

setq
     Set variable values, using the function setq like a command (see Setting Variables (GNU Emacs Lisp Reference Manual)).

source
     Source an Eshell file in a subshell environment.  This is not to be confused with the command ., which sources a file in the current environment.

time
     Show the time elapsed during a command's execution.

umask
     Set or view the default file permissions for newly created files and directories.

unset
     Unset one or more variables.  As with set, a variable name can be a symbol, in which case it refers to a Lisp variable, or a string, referring to an environment variable.

wait
     Wait until a process has successfully completed.

which
     Identify a command and its location.

whoami
     Print the current user.  This Eshell version of whoami supports Tramp.

Defining new built-in commands
------------------------------

While Eshell can run Lisp functions directly as commands, it may be more convenient to provide a special built-in command for Eshell.  Built-in commands are just ordinary Lisp functions designed to be called from Eshell.  When defining an Eshell-specific version of an existing function, you can give that function a name starting with eshell/ so that Eshell knows to use it.

 -- Macro: eshell-eval-using-options name macro-args options body...
     This macro processes a list of MACRO-ARGS for the command NAME using a set of command line OPTIONS.  If the arguments are parsed successfully, it will store the resulting values in local symbols and execute BODY; any remaining arguments will be available in the locally let-bound variable args.  The return value is the value of the last form in BODY.

     If an unknown option was passed in MACRO-ARGS and an external command was specified (see below), this macro will start a process for that command and throw the tag eshell-external with the new process as its value.

     OPTIONS should be a list beginning with one or more elements of the following form, with each element representing a particular command-line switch:

          (SHORT LONG VALUE SYMBOL HELP-STRING)

     short
          This element, if non-nil, should be a character to be used as a short switch, like -SHORT.  At least one of this element and LONG must be non-nil.

     long
          This element, if non-nil, should be a string to be used as a long switch, like --LONG.

     value
          This element is the value associated with the option.  It can be either:

          t
               The option needs a value to be specified after the switch.

          nil
               The option is given the value t.

          anything else
               The option is given the specified value.

     symbol
          This element is the Lisp symbol that will be bound to VALUE.  If SYMBOL is nil, specifying this switch will instead call eshell-show-usage, and so is appropriate for an option like --help.

     help-string
          This element is a documentation string for the option, which will be displayed when eshell-show-usage is invoked.

     After the list of command-line switch elements, OPTIONS can include additional keyword arguments to control how eshell-eval-using-options behaves.  Some of these take arguments, while others don't.  The recognized keywords are:

     :external STRING
          Specify STRING as an external command to run if there are unknown switches in MACRO-ARGS.

     :usage STRING
          Set STRING as the initial part of the command's documentation string.  It appears before the options are listed.

     :post-usage STRING
          Set STRING to be the (optional) trailing part of the command's documentation string.  It appears after the list of options, but before the final part of the documentation about the associated external command, if there is one.

     :show-usage
          If present, then show the usage message if the command is called with no arguments.

     :preserve-args
          Normally, eshell-eval-using-options flattens the list of arguments in MACRO-ARGS and converts each to a string.  If this keyword is present, avoid doing that, instead preserving the original arguments.  This is useful for commands which want to accept arbitrary Lisp objects.

     :parse-leading-options-only
          If present, do not parse dash or switch arguments after the first positional argument.  Instead, treat them as positional arguments themselves.

     For example, you could handle a subset of the options for the ls command like this:

          (eshell-eval-using-options
           "ls" macro-args
           '((?a  nil      nil show-all       "show all files")
             (?I  "ignore" t   ignore-pattern "ignore files matching pattern")
             (nil "help"   nil nil            "show this help message")
           :external "ls"
           :usage "[OPTION]... [FILE]...
            List information about FILEs (the current directory by default).")
           ;; List the files in ARGS somehow...
           )

Variables
=========

Since Eshell is a combination of an Emacs REPL and a command shell, it can refer to variables from two different sources: ordinary Emacs Lisp variables, as well as environment variables.  By default, when using a variable in Eshell, it will first look in the list of built-in variables, then in the list of environment variables, and finally in the list of Lisp variables.  If you would prefer to use Lisp variables over environment variables, you can set eshell-prefer-lisp-variables to t.

You can set variables in a few different ways.  To set a Lisp variable, you can use the command setq NAME VALUE, which works much like its Lisp counterpart (see Setting Variables (The Emacs Lisp Reference Manual)).  To set an environment variable, use export NAME=VALUE.  You can also use set VARIABLE VALUE, which sets a Lisp variable if VARIABLE is a symbol, or an environment variable if it's a string (see Arguments).  Finally, you can temporarily set environment variables for a single command with NAME=VALUE COMMAND ....  This is equivalent to:

     {
       export NAME=VALUE
       COMMAND ...
     }

Built-in variables
------------------

Eshell knows a few built-in variables:

$PWD
$+
     This variable always contains the current working directory.

$OLDPWD
$-
     This variable always contains the previous working directory (the current working directory from before the last cd command). When using $-, you can also access older directories in the directory ring via subscripting, e.g. $-[1] refers to the working directory before the previous one.

$PATH
     This specifies the directories to search for executable programs.  Its value is a string, separated by ":" for Unix and GNU systems, and ";" for MS systems.  This variable is connection-aware, so whenever you change the current directory to a different host (see Remote Files (The GNU Emacs Manual)), the value will automatically update to reflect the search path on that host.

$_
     This refers to the last argument of the last command.  With a subscript, you can access any argument of the last command.  For example, $_[1] refers to the second argument of the last command (excluding the command name itself).

$$
     This is the result of the last command.  For external commands, it is t if the exit code was 0 or nil otherwise.

$?
     This variable contains the exit code of the last command.  If the last command was a Lisp function, it is 0 for successful completion or 1 otherwise.  If eshell-lisp-form-nil-is-failure is non-nil, then a command with a Lisp form, like (COMMAND ARGS...), that returns nil will set this variable to 2.

$COLUMNS
$LINES
     These variables tell the number of columns and lines, respectively, that are currently visible in the Eshell window.  They are both copied to the environment, so external commands invoked from Eshell can consult them to do the right thing.

$INSIDE_EMACS
     This variable indicates to external commands that they are being invoked from within Emacs so they can adjust their behavior if necessary.  By default, its value is EMACS-VERSION,eshell.  Other parts of Emacs, such as Tramp, may add extra information to this value.

See Aliases, for the built-in variables $*, $1, $2, ..., in alias definitions.

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).

Note that unlike aliases in Bash, arguments must be handled explicitly.  Typically the alias definition would end in $* to pass all arguments along.  More selective use of arguments via $1, $2, etc., is also possible.  For example, alias mcd 'mkdir $1 && cd $1' would cause mcd foo to create and switch to a directory called foo.

Remote Access
=============

Since Eshell uses Emacs facilities for most of its functionality, you can access remote hosts transparently.  To connect to a remote host, simply cd into it:

     ~ $ cd /ssh:user@remote:
     /ssh:user@remote:~ $

Additionally, built-in Eshell commands (see Built-ins) and ordinary Lisp functions accept remote file names, so you can access them even without explicitly connecting first.  For example, to print the contents of a remote file, you could type cat /ssh:user@remote:~/output.log.  However, this means that when using built-in commands or Lisp functions from a remote directory, you must be careful about specifying absolute file names: cat /var/output.log will always print the contents of your local /var/output.log, even from a remote directory.  If you find this behavior annoying, you can enable the optional electric forward slash module (see Electric forward slash).

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.

When history event designators are enabled (by adding eshell-expand-history-references to eshell-expand-input-functions), !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 previous or next line that begins with that string.

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, the pattern will be removed from the input line, and replaced by the completion.

If you want to see the entire list of possible completions (e.g. when it's below the completion-cycle-threshold), press M-?.

pcomplete
---------

Pcomplete, short for programmable completion, is the completion library originally written for Eshell, but usable for command completion (Command completion, as opposed to code completion, which is beyond the scope of pcomplete.) 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.

Control Flow
============

Because Eshell commands can not (easily) be combined with Lisp forms, Eshell provides command-oriented control flow statements for convenience.

Most of Eshell's control flow statements accept a CONDITIONAL. This can take a few different forms.  If CONDITIONAL is a dollar expansion, the condition is satisfied if the result is a non-nil value.  If CONDITIONAL is a { SUBCOMMAND } or (LISP FORM), the condition is satisfied if the command's exit status is 0.

if CONDITIONAL { TRUE-COMMANDS }
if CONDITIONAL { TRUE-COMMANDS } { FALSE-COMMANDS }
     Evaluate TRUE-COMMANDS if CONDITIONAL is satisfied; otherwise, evaluate FALSE-COMMANDS.

unless CONDITIONAL { FALSE-COMMANDS }
unless CONDITIONAL { FALSE-COMMANDS } { TRUE-COMMANDS }
     Evaluate FALSE-COMMANDS if CONDITIONAL is not satisfied; otherwise, evaluate TRUE-COMMANDS.

while CONDITIONAL { COMMANDS }
     Repeatedly evaluate COMMANDS so long as CONDITIONAL is satisfied.

until CONDITIONAL { COMMANDS }
     Repeatedly evaluate COMMANDS until CONDITIONAL is satisfied.

for VAR in LIST... { COMMANDS }
     Iterate over each element of LIST, storing the element in VAR and evaluating COMMANDS.  If LIST is not a list, treat it as a list of one element.  If you specify multiple LISTS, this will iterate over each of them in turn.

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.

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. (Eshell has no string-manipulation expansions because the Elisp library already provides many functions for this.)  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. (E.g., entering just $VAR at the prompt is equivalent to entering the value of VAR at the prompt.)

You can concatenate expansions with regular string arguments or even other expansions.  In the simplest case, when the expansion returns a string value, this is equivalent to ordinary string concatenation; for example, ${echo "foo"}bar returns foobar.  The exact behavior depends on the types of each value being concatenated:

both strings
     Concatenate both values together.

one or both numbers
     Concatenate the string representation of each value, converting back to a number if possible.

one or both (non-nil) lists
     Concatenate ``adjacent'' elements of each value (possibly converting back to a number as above).  For example, $(list "a" "b")c returns ("a" "bc").

anything else
     Concatenate the string representation of each value.

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"

$'VAR'
     Expands to the value bound to VAR.  This is useful to disambiguate the variable name when concatenating it with another value, such as $"VAR"-suffix.

$(LISP)
     Expands to the result of evaluating the S-expression (LISP).  On its own, this is identical to just (LISP), but with the $, it can be used inside double quotes or within a longer string, such as /some/path/$(LISP).txt.

${COMMAND}
     Returns the output of COMMAND, which can be any valid Eshell command invocation, and may even contain expansions.  Similar to $(LISP), this is identical to {COMMAND} when on its own, but the $ allows it to be used inside double quotes or as part of a string.

     Normally, the output is split line-by-line, returning a list (or the first element if there's only one line of output); if eshell-convert-numeric-arguments is non-nil and every line of output looks like a number, convert each line to a number. However, when this expansion is surrounded by double quotes, it returns the output as a single string instead.

$<COMMAND>
     As with ${COMMAND}, evaluates the Eshell command invocation COMMAND, but writes the output to a temporary file and returns the file name.

$EXPR[I...]
     Expands to the Ith element of the result of EXPR, an expression in one of the above forms listed here.  If multiple indices are supplied, this will return a list containing the elements for each index.  The exact behavior depends on the type of EXPR's value:

     a sequence
          Expands to the element at the (zero-based) index I of the sequence (see Sequences Arrays Vectors (The Emacs Lisp Reference Manual)).

     a string
          Split the string at whitespace, and then expand to the Ith element of the resulting sequence.

     an alist
          If I is a non-numeric value, expand to the value associated with the key "I" in the alist.  For example, if VAR is (("dog" . "fido") ("cat" . "felix")), then $VAR[dog] expands to "fido".  Otherwise, this behaves as with sequences; e.g., $VAR[0] expands to ("dog" . "fido").  See Association Lists (The Emacs Lisp Reference Manual).

     anything else
          Signals an error.

     Multiple sets of indices can also be specified.  For example, if VAR is ((1 2) (3 4)), then $VAR[0][1] will expand to 2, i.e. the second element of the first list member (all indices are zero-based).

$EXPR[REGEXP I...]
     As above (when EXPR expands to a string), but use REGEXP to split the string.  REGEXP can be any form other than a number.  For example, $VAR[: 0] will return the first element of a colon-delimited string.

$#EXPR
     Expands to the length of the result of EXPR, an expression in one of the above forms.  For example, $#VAR returns the length of the variable VAR and $#VAR[0] returns the length of the first element of VAR.  Again, signals an error if the result of EXPR is not a string or a sequence.

Globbing
========

Eshell's globbing syntax is very similar to that of Zsh (see Filename Generation (The Z Shell Manual)).  Users coming from Bash can still use Bash-style globbing, as there are no incompatibilities.

By default, globs are case sensitive, except on MS-DOS/MS-Windows systems.  You can control this behavior via the eshell-glob-case-insensitive option.  You can further customize the syntax and behavior of globbing in Eshell via the Customize group eshell-glob (see Easy Customization (The GNU Emacs Manual)).

*
     Matches any string (including the empty string).  For example, *.el matches any file with the .el extension.

?
     Matches any single character.  For example, ?at matches cat and bat, but not goat.

**/
     Matches zero or more subdirectories in a file name.  For example, **/foo.el matches foo.el, bar/foo.el, bar/baz/foo.el, etc.  Note that this cannot be combined with any other patterns in the same file name segment, so while foo/**/bar.el is allowed, foo**/bar.el is not.

***/
     Like **/, but follows symlinks as well.

[ ... ]
     Defines a character set (see Regexps (The GNU Emacs Manual)).  A character set matches characters between the two brackets; for example, [ad] matches a and d.  You can also include ranges of characters in the set by separating the start and end with -.  Thus, [a-z] matches any lower-case ASCII letter.  Note that, unlike in Zsh, character ranges are interpreted in the Unicode codepoint order, not in the locale-dependent collation order.

     Additionally, you can include character classes in a character set.  A [: and balancing :] enclose a character class inside a character set.  For instance, [[:alnum:]] matches any letter or digit.  See Char Classes (The Emacs Lisp Reference Manual), for a list of character classes.

[^ ... ]
     Defines a complemented character set.  This behaves just like a character set, but matches any character except the ones specified.

( ... )
     Defines a group.  A group matches the pattern between ( and ).  Note that a group can only match a single file name component, so a / inside a group will signal an error.

X|Y
     Inside of a group, matches either X or Y.  For example, e(m|sh)-* matches any file beginning with em- or esh-.

X#
     Matches zero or more copies of the glob pattern X.  For example, fo#.el matches f.el, fo.el, foo.el, etc.

X##
     Matches one or more copies of the glob pattern X.  Thus, fo#.el matches fo.el, foo.el, fooo.el, etc.

X~Y
     Matches anything that matches the pattern X but not Y. For example, [[:digit:]]#~4? matches 1 and 12, but not 42.  Note that unlike in Zsh, only a single ~ operator can be used in a pattern, and it cannot be inside of a group like (X~Y).

Argument Predication and Modification
=====================================

Eshell supports argument predication, to filter elements of a glob, and argument modification, to manipulate argument values. These are similar to glob qualifiers in Zsh (see Glob Qualifiers (The Z Shell Manual)).

Predicates and modifiers are introduced with (FILTERS) after any list argument, where FILTERS is a list of predicates or modifiers.  For example, *(.) expands to all regular files in the current directory and *(^@:U^u0) expands to all non-symlinks not owned by root, upper-cased.

Some predicates and modifiers accept string parameters, such as *(u'USER'), which matches all files owned by USER. These parameters must be surrounded by delimiters; you can use any of the following pairs of delimiters: "...", '...', /.../, |...|, (...), [...], <...>, or {...}.

You can customize the syntax and behavior of predicates and modifiers in Eshell via the Customize group eshell-pred (see Easy Customization (The GNU Emacs Manual)).

Argument Predicates
-------------------

You can use argument predicates to filter lists of file names based on various properties of those files.  This is most useful when combined with globbing, but can be used on any list of files names.  Eshell supports the following argument predicates:

/
     Matches directories.

. (Period)
     Matches regular files.

@
     Matches symbolic links.

=
     Matches sockets.

p
     Matches named pipes.

%
     Matches block or character devices.

%b
     Matches block devices.

%c
     Matches character devices.

*
     Matches regular files that can be executed by the current user.

r

A

R
     Matches files that are readable by their owners (r), their groups (A), or the world (R).

w

I

W
     Matches files that are writable by their owners (w), their groups (I), or the world (W).

x

E

X
     Matches files that are executable by their owners (x), their groups (E), or the world (X).

s
     Matches files with the setuid flag set.

S
     Matches files with the setgid flag set.

t
     Matches files with the sticky bit set.

U
     Matches files owned by the current effective user ID.

G
     Matches files owned by the current effective group ID.

l[+-]N
     Matches files with N links.  With + (or -), matches files with more than (or less than) N links, respectively.

uUID

u'USER-NAME'
     Matches files owned by user ID UID or user name USER-NAME.

gGID

g'GROUP-NAME'
     Matches files owned by group ID GID or group name GROUP-NAME.

a[UNIT][+-]N

a[+-]'FILE'
     Matches files last accessed exactly N days ago.  With + (or -), matches files accessed more than (or less than) N days ago, respectively.

     With UNIT, N is a quantity in that unit of time, so aw-1 matches files last accessed within one week.  UNIT can be M (30-day months), w (weeks), h (hours), m (minutes), or s (seconds).

     If FILE is specified instead, compare against the modification time of file.  Thus, a-'hello.txt' matches all files accessed after hello.txt was last accessed.

m[UNIT][+-]N

m[+-]'FILE'
     Like a, but examines modification time.

c[UNIT][+-]N

c[+-]'FILE'
     Like a, but examines status change time.

L[UNIT][+-]N
     Matches files exactly N bytes in size.  With + (or -), matches files larger than (or smaller than) N bytes, respectively.

     With UNIT, N is a quantity in that unit of size, so Lm+5 matches files larger than 5 MiB in size.  UNIT can be one of the following (case-insensitive) characters: m (megabytes), k (kilobytes), or p (512-byte blocks).

The ^ and - operators are not argument predicates themselves, but they modify the behavior of all subsequent predicates. ^ inverts the meaning of subsequent predicates, so *(^RWX) expands to all files whose permissions disallow the world from accessing them in any way (i.e., reading, writing to, or modifying them).  When examining a symbolic link, - applies the subsequent predicates to the link's target instead of the link itself.

Argument Modifiers
------------------

You can use argument modifiers to manipulate argument values.  For example, you can sort lists, remove duplicate values, capitalize words, etc.  All argument modifiers are prefixed by :, so $exec-path(:h:u:x/^\/home/) lists all of the unique parent directories of the elements in exec-path, excluding those in /home.

E
     Re-evaluates the value as an Eshell argument.  For example, if FOO is "${echo hi}", then the result of $foo(:E) is hi.

L
     Converts the value to lower case.

U
     Converts the value to upper case.

C
     Capitalizes the value.

h
     Treating the value as a file name, gets the directory name (the ``head'').  For example, foo/bar/baz.el(:h) expands to foo/bar/.

t
     Treating the value as a file name, gets the base name (the ``tail''). For example, foo/bar/baz.el(:t) expands to baz.el.

e
     Treating the value as a file name, gets the final extension of the file, excluding the dot.  For example, foo.tar.gz(:e) expands to gz.

r
     Treating the value as a file name, gets the file name excluding the final extension.  For example, foo/bar/baz.tar.gz(:r) expands to foo/bar/baz.tar.

q
     Marks that the value should be interpreted by Eshell literally, so that any special characters like $ no longer have any special meaning.

s/PATTERN/REPLACE/
     Replaces the first instance of the regular expression PATTERN with REPLACE.  Signals an error if no match is found.

     As with other modifiers taking string parameters, you can use different delimiters to separate PATTERN and REPLACE, such as s'...'...', s[...][...], or even s[...]/.../.

gs/PATTERN/REPLACE/
     Replaces all instances of the regular expression PATTERN with REPLACE.

i/PATTERN/
     Filters a list of values to include only the elements matching the regular expression PATTERN.

x/PATTERN/
     Filters a list of values to exclude all the elements matching the regular expression PATTERN.

S

S/PATTERN/
     Splits the value using the regular expression PATTERN as a delimiter.  If PATTERN is omitted, split on spaces.

j

j/DELIM/
     Joins a list of values, inserting the string DELIM between each value.  If DELIM is omitted, use a single space as the delimiter.

o
     Sorts a list of strings in ascending lexicographic order, comparing pairs of characters according to their character codes (see Text Comparison (The Emacs Lisp Reference Manual)).

O
     Sorts a list of strings in descending lexicographic order.

u
     Removes any duplicate elements from a list of values.

R
     Reverses the order of a list of values.

Input/Output
************

Since Eshell does not communicate with a terminal like most command shells, IO is a little different.

Visual Commands
===============

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 such programs in Emacs's terminal emulator.

Programs that need a terminal to display output properly are referred to in this manual as ``visual commands'', because they are not simply line-oriented.  You must tell Eshell which commands are visual, by adding them to eshell-visual-commands; for commands that are visual for only certain sub-commands -- e.g., git log but not git status -- use eshell-visual-subcommands; and for commands that are visual only when passed certain options, use eshell-visual-options.

Caution: Some tools such as Git use the pager less by default to paginate their output but call it with its -F option.  This option causes less to echo the output instead of paginating it if the output is less than one page long.  This causes undesirable behavior if, e.g., git diff, is defined as a visual subcommand. It'll work if the output is big enough and fail if it is less than one page long.  If that occurs to you, search for configuration options for calling less without the -F option.  For Git, you can do that using git config --global core.pager 'less -+F'.

If you want the buffers created by visual programs killed when the program exits, customize the variable eshell-destroy-buffer-when-process-dies to a non-nil value; the default is nil.

Redirection
===========

Redirection in Eshell is similar to that of other command shells.  You can use the output redirection operators > and >>, but there is not yet any support for input redirection.  In the cases below, FD specifies the file descriptor to redirect; if not specified, file descriptor 1 (standard output) will be used by default.

> DEST
FD> DEST
     Redirect output to DEST, overwriting its contents with the new output.

>> DEST
FD>> DEST
     Redirect output to DEST, appending it to the existing contents of DEST.

>>> DEST
FD>>> DEST
     Redirect output to DEST, inserting it at the current mark if DEST is a buffer, at the beginning of the file if DEST is a file, or otherwise behaving the same as >>.

&> DEST
>& DEST
     Redirect both standard output and standard error to DEST, overwriting its contents with the new output.

&>> DEST
>>& DEST
     Redirect both standard output and standard error to DEST, appending it to the existing contents of DEST.

&>>> DEST
>>>& DEST
     Redirect both standard output and standard error to DEST, inserting it like with >>> DEST.

>&OTHER-FD
FD>&OTHER-FD
     Duplicate the file descriptor OTHER-FD to FD (or 1 if unspecified).  The order in which this is used is significant, so

          COMMAND > FILE 2>&1

     redirects both standard output and standard error to FILE, whereas

          COMMAND 2>&1 > FILE

     only redirects standard output to FILE (and sends standard error to the display via standard output's original handle).

Eshell supports redirecting output to several different types of targets:

  * files, including virtual targets (see below);

  * buffers (see Buffers (GNU Emacs Lisp Reference Manual));

  * markers (see Markers (GNU Emacs Lisp Reference Manual));

  * processes (see Processes (GNU Emacs Lisp Reference Manual)); and

  * symbols (see Symbols (GNU Emacs Lisp Reference Manual)).

Virtual Targets
---------------

Virtual targets are mapping of device names to functions.  Eshell comes with four virtual devices:

/dev/null
     Does nothing with the output passed to it.

/dev/eshell
     Writes the text passed to it to the display.

/dev/kill
     Adds the text passed to it to the kill ring.

/dev/clip
     Adds the text passed to it 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 for >, append for >>, or insert for >>>--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.

Pipelines
=========

As with most other shells, Eshell supports pipelines to pass the output of one command the input of the next command.  You can send the standard output of one command to the standard input of another using the | operator.  For example,

     ~ $ echo hello | rev
     olleh

To send both the standard output and standard error of a command to another command's input, you can use the |& operator.

Running Shell Pipelines Natively
--------------------------------

When constructing shell pipelines that will move a lot of data, it is a good idea to bypass Eshell's own pipelining support and use the operating system shell's instead.  This is especially relevant when executing commands on a remote machine using Eshell's Tramp integration: using the remote shell's pipelining avoids copying the data which will flow through the pipeline to local Emacs buffers and then right back again.

Eshell recognizes a special syntax to make it easier to convert pipelines so as to bypass Eshell's pipelining.  Prefixing at least one |, < or > with an asterisk marks a command as intended for the operating system shell.  To make it harder to invoke this functionality accidentally, it is also required that the asterisk be preceded by whitespace or located at the start of input.  For example,

      cat *.ogg *| my-cool-decoder >file

Executing this command will not copy all the data in the *.ogg files, nor the decoded data, into Emacs buffers, as would normally happen.

The command is interpreted as extending up to the next | character which is not preceded by an unescaped asterisk following whitespace, or the end of the input if there is no such character. Thus, all < and > redirections occurring before the next asterisk-unprefixed | are implicitly prefixed with (whitespace and) asterisks.  An exception is that Eshell-specific redirects right at the end of the command are excluded.  This allows input like this:

      foo *| baz >#<buffer quux>

which is equivalent to input like this:

      sh -c "foo | baz" >#<buffer quux>

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. (ERC provides a similar module facility.)

Optional modules
================

In addition to the various modules enabled by default (documented above), Eshell provides several other modules which are not enabled by default.  If you want to enable these, you can add them to eshell-modules-list.

Key rebinding
-------------

This module allows for special keybindings that only take effect while the point is in a region of input text.  The default keybindings mimic the bindings used in other shells when the user is editing new input text.  To enable this module, add eshell-rebind to eshell-modules-list.

For example, it binds C-a to move to the beginning of the input text, C-u to kill the current input text, and C-w to backward-kill-word.  If the history module is enabled, it also binds C-p and C-n to move through the input history.

If eshell-confine-point-to-input is non-nil, this module prevents certain commands from causing the point to leave the input area, such as backward-word, previous-line, etc.

Smart scrolling
---------------

This module combines the facility of normal, modern shells with some of the edit/review concepts inherent in the design of Plan 9's 9term. To enable it, add eshell-smart to eshell-modules-list.

  * When you invoke a command, it is assumed that you want to read the output of that command.

  * If the output is not what you wanted, it is assumed that you will want to edit, and then resubmit a refined version of that command.

  * If the output is valid, pressing any self-inserting character key will jump to end of the buffer and insert that character, in order to begin entry of a new command.

  * If you show an intention to edit the previous command -- by moving around within it -- then the next self-inserting characters will insert *there*, instead of at the bottom of the buffer.

  * If you show an intention to review old commands, such as M-p or M-r, point will jump to the bottom of the buffer before invoking that command.

  * If none of the above has happened yet (i.e. your point is just sitting on the previous command), you can use SPC and BACKSPACE (or Delete) to page forward and backward through the output of the last command only.  It will constrain the movement of the point and window so that the maximum amount of output is always displayed at all times.

  * While output is being generated from a command, the window will be constantly reconfigured (until it would otherwise make no difference) in order to always show you the most output from the command possible. This happens if you change window sizes, scroll, etc.

Electric forward slash
----------------------

To help with supplying absolute file name arguments to remote commands, you can add the eshell-elecslash module to eshell-modules-list.  Then, typing / as the first character of a command line argument will automatically insert the Tramp prefix /method:host:.  If this is not what you want (e.g. because you want to refer to a local file), you can type another / to undo the automatic insertion.  Typing ~/ also inserts the Tramp prefix.  The automatic insertion applies only when default-directory is remote and the command is a Lisp function. In particular, typing arguments to external commands doesn't insert the prefix.

The result is that in most cases of supplying absolute file name arguments to commands you should see the Tramp prefix inserted automatically only when that's what you'd reasonably expect.  This frees you from having to keep track of whether commands are Lisp functions or external when typing command line arguments.  For example, suppose you execute

      cd /ssh:root@example.com:
      find /etc -name "*gnu*"

and in reviewing the output of the command, you identify a file /etc/gnugnu that should be moved somewhere else.  So you type

      mv /etc/gnugnu /tmp

But since mv refers to the local Lisp function eshell/mv, not a remote shell command, to say this is to request that the local file /etc/gnugnu be moved into the local /tmp directory.  After you add eshell-elecslash to eshell-modules-list, then when you type the above mv invocation you will get the following input, which is what you intended:

      mv /ssh:root@example.com:/etc/gnugnu /ssh:root@example.com:/tmp

The code that determines whether or not the Tramp prefix should be inserted uses simple heuristics.  A limitation of the current implementation is that it inspects whether only the command at the very beginning of input is a Lisp function or external program.  Thus when chaining commands with the operators &&, ||, | and ;, the electric forward slash is active only within the first command.

Tramp extensions
----------------

This module adds built-in commands that use Tramp to handle running other commands as different users, replacing the corresponding external commands.  To enable it, add eshell-tramp to eshell-modules-list.

su
sudo
doas
     Uses TRAMP's su, sudo, or doas method (see Inline methods (The Tramp Manual)) to run a command via su, sudo, or doas.

Extra built-in commands
-----------------------

This module provides several extra built-in commands documented below, primarily for working with lists of strings in Eshell.  To enable it, add eshell-xtra to eshell-modules-list.

count
     A wrapper around the function cl-count (see Searching Sequences (GNU Emacs Common Lisp Emulation)).  This command can be used for comparing lists of strings.

expr
     An implementation of expr using the Calc package. See The GNU Emacs Calculator.

ff
     Shorthand for the the function find-name-dired (see Dired and Find (The Emacs Editor)).

gf
     Shorthand for the the function find-grep-dired (see Dired and Find (The Emacs Editor)).

intersection
     A wrapper around the function cl-intersection (see Lists as Sets (GNU Emacs Common Lisp Emulation)).  This command can be used for comparing lists of strings.

mismatch
     A wrapper around the function cl-mismatch (see Searching Sequences (GNU Emacs Common Lisp Emulation)).  This command can be used for comparing lists of strings.

set-difference
     A wrapper around the function cl-set-difference (see Lists as Sets (GNU Emacs Common Lisp Emulation)).  This command can be used for comparing lists of strings.

set-exclusive-or
     A wrapper around the function cl-set-exclusive-or (see Lists as Sets (GNU Emacs Common Lisp Emulation)).  This command can be used for comparing lists of strings.

substitute
     A wrapper around the function cl-substitute (see Sequence Functions (GNU Emacs Common Lisp Emulation)).  This command can be used for comparing lists of strings.

union
     A wrapper around the function cl-union (see Lists as Sets (GNU Emacs Common Lisp Emulation)).  This command can be used for comparing lists of strings.

Writing a module
================

An Eshell module is defined the same as any other library but with two additional requirements: first, the module's source file should be named em-NAME.el; second, the module must define an autoloaded Customize group (see Customization (The Emacs Lisp Reference Manual)) with eshell-module as the parent group. In order to properly autoload this group, you should wrap its definition with progn as follows:

     ;;;###autoload
     (progn
     (defgroup eshell-my-module nil
       "My module lets you do very cool things in Eshell."
       :tag "My module"
       :group 'eshell-module))

Even if you don't have any Customize options in your module, you should still define the group so that Eshell can include your module in the Customize interface for eshell-modules-list.

Bugs and ideas
**************

If you find a bug or misfeature, don't hesitate to report it, by using M-x report-emacs-bug.  The same applies to feature requests. It is best to discuss one thing at a time.  If you find several unrelated bugs, please report them separately.

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

Differentiate between aliases and functions

     Allow for a Bash-compatible syntax, such as:

          alias arg=blah
          function arg () { blah $* }

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

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-pipelines 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

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}/binTAB 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.

(+ 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}

Create a mode eshell-browse

     It would treat the Eshell buffer as an 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?

Make a customizable syntax table for redirects

     This way, 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, ssh, 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 / more electric

     so that it automatically expands and corrects file names, beyond what the em-elecslash module is able to do.  Or make file name completion for Pcomplete auto-expand /u/i/stdTAB to /usr/include/stdTAB.

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.

GNU Free Documentation License
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     [file doclicense.texi not included]