eshell / eshell.el

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;;; eshell --- the Emacs command shell

;; Copyright (C) 1999, 2000 Free Software Foundation

;; Author: John Wiegley <johnw@gnu.org>
;; Keywords: processes

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

(provide 'eshell)

(eval-when-compile (require 'esh-maint))

(defgroup eshell nil
  "Eshell is a command shell implemented entirely in Emacs Lisp.  It
invokes no external processes beyond those requested by the user.  It
is intended to be a functional replacement for command shells such as
bash, zsh, rc, 4dos; since Emacs itself is capable of handling most of
the tasks accomplished by such tools."
  :tag "The Emacs shell"
  :link '(info-link "(eshell)The Emacs shell")
  :version "21.1"
  :group 'applications)

;;; Commentary:

;;;_* What does Eshell offer you?
;;
;; Despite the sheer fact that running an Emacs shell can be fun, here
;; are a few of the unique features offered by Eshell:
;;
;; @ Integration with the Emacs Lisp programming environment
;;
;; @ A high degree of configurability
;;
;; @ The ability to have the same shell on every system Emacs has been
;;   ported to. Since Eshell imposes no external requirements, and
;;   relies upon only the Lisp functions exposed by Emacs, it is quite
;;   operating system independent. Several of the common UNIX
;;   commands, such as ls, mv, rm, ln, etc., have been implemented in
;;   Lisp in order to provide a more consistent work environment.
;;
;; For those who might be using an older version of Eshell, version
;; 2.1 represents an entirely new, module-based architecture. It
;; supports most of the features offered by modern shells. Here is a
;; brief list of some of its more visible features:
;;
;; @ Command argument completion (tcsh, zsh)
;; @ Input history management (bash)
;; @ Intelligent output scrolling
;; @ Psuedo-devices (such as "/dev/clip" for copying to the clipboard)
;; @ Extended globbing (zsh)
;; @ Argument and globbing predication (zsh)
;; @ I/O redirection to buffers, files, symbols, processes, etc.
;; @ Many niceties otherwise seen only in 4DOS
;; @ Alias functions, both Lisp and Eshell-syntax
;; @ Piping, sequenced commands, background jobs, etc...
;;
;;;_* Eshell is free software
;;
;; Eshell is free software; you can redistribute it and/or modify it
;; under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.
;;
;; This program is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;; General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with Eshell; see the file COPYING.  If not, write to the Free
;; Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
;; 02111-1307, USA.
;;
;;;_* How to begin
;;
;; To start using Eshell, add the following to your .emacs file:
;;
;;   (load "eshell-auto")
;;
;; This will define all of the necessary autoloads.
;;
;; Now type `M-x eshell'.  See the INSTALL file for full installation
;; instructions.
;;
;;;_* Philosophy
;;
;; A shell is a layer which metaphorically surrounds the kernel, or
;; heart of an operating system.  This kernel can be seen as an engine
;; of pure functionality, waiting to serve, while the user programs
;; take advantage of that functionality to accomplish their purpose.
;;
;; The shell's role is to make that functionality accessible to the
;; user in an unformed state.  Very roughly, it associates kernel
;; functionality with textual commands, allowing the user to interact
;; with the operating system via linguistic constructs.  Process
;; invocation is perhaps the most significant form this takes, using
;; the kernel's `fork' and `exec' functions.
;;
;; Other programs also interact with the functionality of the kernel,
;; but these user applications typically offer a specific range of
;; functionality, and thus are not classed as "shells" proper.
;; (What they lose in quiddity, they gain in rigidity).
;;
;; Emacs is also a user application, but it does make the
;; functionality of the kernel accessible through an interpreted
;; language -- namely, Lisp.  For that reason, there is little
;; preventing Emacs from serving the same role as a modern shell.  It
;; too can manipulate the kernel in an unpredetermined way to cause
;; system changes.  All it's missing is the shell-ish linguistic
;; model.
;;
;; Enter Eshell.  Eshell translates "shell-like" syntax into Lisp
;; in order to exercise the kernel in the same manner as typical
;; system shells.  There is a fundamental difference here, however,
;; although it may seem subtle at first...
;;
;; Shells like csh and Bourne shell were written several decades ago,
;; in different times, under more restrictive circumstances.  This
;; confined perspective shows itself in the paradigm used by nearly
;; all command-line shells since.  They are linear in conception, byte
;; stream-based, sequential, and confined to movement within a single
;; host machine.
;;
;; Emacs, on the other hand, is more than just a limited translator
;; that can invoke subprocesses and redirect file handles.  It also
;; manages character buffers, windowing frames, network connections,
;; registers, bookmarks, processes, etc.  In other words, it's a very
;; multi-dimensional environment, within which eshell emulates a highly
;; linear methodology.
;;
;; Taking a moment, let's look at how this could affect the future of
;; a shell allowed to develop in such a wider field of play:
;;
;; @ There is no reason why directory movement should be linear, and
;;   confined to a single file-system.  Emacs, through w3 and ange-ftp,
;;   has access to the entire Web.  Why not allow a user to cd to
;;   multiple directories simultaneously, for example?  It might make
;;   some tasks easier, such as diff'ing files separated by very long
;;   pathnames.
;;
;; @ Data sources are available from anywhere Emacs can derive
;;   information from: not just from files or the output of other
;;   processes.
;;
;; @ Multiple shell invocations all share the same environment -- even
;;   the same process list!  It would be possible to have "process
;;   views", so that one buffer is watching standard output, another
;;   standard error, and another the result of standard output grep'd
;;   through a regular expression...
;;
;; @ It is not necessary to "leave" the shell, losing all input and
;;   output history, environment variables, directory stack, etc.
;;   Emacs could save the contents of your eshell environment, and
;;   restore all of it (or at least as much as possible) each time you
;;   restart.  This could occur automatically, without requiring
;;   complex initialization scripts.
;;
;; @ Typos occur all of the time; many of them are repeats of common
;;   errors, such as 'dri' for `dir'.  Since executing non-existent
;;   programs is rarely the intention of the user, eshell could prompt
;;   for the replacement string, and then record that in a database of
;;   known misspellings. (Note: The typo at the beginning of this
;;   paragraph wasn't discovered until two months after I wrote the
;;   text; it was not intentional).
;;
;; @ Emacs' register and bookmarking facilities can be used for
;;   remembering where you've been, and what you've seen -- to varying
;;   levels of persistence.  They could perhaps even be tied to
;;   specific "moments" during eshell execution, which would include
;;   the environment at that time, as well as other variables.
;;   Although this would require functionality orthogonal to Emacs'
;;   own bookmarking facilities, the interface used could be made to
;;   operate very similarly.
;;
;; This presents a brief idea of what the fuller dimensionality of an
;; Emacs shell could offer.  It's not just the language of a shell
;; that determines how it's used, but also the Weltanschauung
;; underlying its design -- and which is felt behind even the smallest
;; feature.  I would hope the freedom provided by using Emacs as a
;; parent environment will invite rich ideas from others.  It
;; certainly feels as though all I've done so far is to tie down the
;; horse, so to speak, so that he will run at a man's pace.
;;
;;;_* Influences
;;
;; The author of Eshell has been a long-time user of the following
;; shells, all of which contributed to Eshell's design:
;;
;; @ rc
;; @ bash
;; @ zsh
;; @ sh
;; @ 4nt
;; @ csh

;;;_* User Options
;;
;; The following user options modify the behavior of Eshell overall.

(load "esh-util" nil t)

(defsubst eshell-add-to-window-buffer-names ()
  "Add `eshell-buffer-name' to `same-window-buffer-names'."
  (add-to-list 'same-window-buffer-names eshell-buffer-name))

(defsubst eshell-remove-from-window-buffer-names ()
  "Remove `eshell-buffer-name' from `same-window-buffer-names'."
  (setq same-window-buffer-names
	(delete eshell-buffer-name same-window-buffer-names)))

(defcustom eshell-load-hook nil
  "*A hook run once Eshell has been loaded."
  :type 'hook
  :group 'eshell)

(defcustom eshell-unload-hook
  '(eshell-remove-from-window-buffer-names
    eshell-unload-all-modules)
  "*A hook run when Eshell is unloaded from memory."
  :type 'hook
  :group 'eshell)

(defcustom eshell-buffer-name "*eshell*"
  "*The basename used for Eshell buffers."
  :set (lambda (symbol value)
	 ;; remove the old value of `eshell-buffer-name', if present
	 (if (boundp 'eshell-buffer-name)
	     (eshell-remove-from-window-buffer-names))
	 (set symbol value)
	 ;; add the new value
	 (eshell-add-to-window-buffer-names)
	 value)
  :type 'string
  :group 'eshell)

(eshell-deftest mode same-window-buffer-names
  "`eshell-buffer-name' is a member of `same-window-buffer-names'"
  (member eshell-buffer-name same-window-buffer-names))

;;;###autoload
(defcustom eshell-directory-name (convert-standard-filename "~/.eshell/")
  "*The directory where Eshell control files should be kept."
  :type 'directory
  :group 'eshell)

(eshell-deftest mode eshell-directory-exists
  "`eshell-directory-name' exists and is writable"
  (file-writable-p eshell-directory-name))

(eshell-deftest mode eshell-directory-modes
  "`eshell-directory-name' has correct access protections"
  (or (eshell-under-windows-p)
      (= (file-modes eshell-directory-name)
	 eshell-private-directory-modes)))

(defcustom eshell-prefer-to-shell nil
  "*If non-nil, \\[shell-command] will use Eshell instead of shell-mode."
  :set (lambda (symbol value)
	 ;; modifying the global keymap directly is odious, but how
	 ;; else to achieve the takeover?
	 (if value
	     (progn
	       (define-key global-map [(meta ?!)] 'eshell-command)
;;;            (define-key global-map [(meta ?|)] 'eshell-command-on-region)
	       )
	   (define-key global-map [(meta ?!)] 'shell-command)
;;;        (define-key global-map [(meta ?|)] 'shell-command-on-region)
	   )
	 (set symbol value))
  :type 'boolean
  :require 'eshell
  :group 'eshell)

;;;_* Running Eshell
;;
;; There are only three commands used to invoke Eshell.  The first two
;; are intended for interactive use, while the third is meant for
;; programmers.  They are:

;;;###autoload
(defun eshell (&optional arg)
  "Create an interactive Eshell buffer.
The buffer used for Eshell sessions is determined by the value of
`eshell-buffer-name'.  If there is already an Eshell session active in
that buffer, Emacs will simply switch to it.  Otherwise, a new session
will begin.  A new session is always created if the the prefix
argument ARG is specified.  Returns the buffer selected (or created)."
  (interactive "P")
  (assert eshell-buffer-name)
  (let ((buf (if arg
		 (generate-new-buffer eshell-buffer-name)
	       (get-buffer-create eshell-buffer-name))))
    ;; Simply calling `pop-to-buffer' will not mimic the way that
    ;; shell-mode buffers appear, since they always reuse the same
    ;; window that that command was invoked from.  To achieve this,
    ;; it's necessary to add `eshell-buffer-name' to the variable
    ;; `same-window-buffer-names', which is done when Eshell is loaded
    (assert (and buf (buffer-live-p buf)))
    (pop-to-buffer buf)
    (unless (fboundp 'eshell-mode)
      (error "`eshell-auto' must be loaded before Eshell can be used"))
    (unless (eq major-mode 'eshell-mode)
      (eshell-mode))
    (assert (eq major-mode 'eshell-mode))
    buf))

(defun eshell-return-exits-minibuffer ()
  (define-key eshell-mode-map [(control ?g)] 'abort-recursive-edit)
  (define-key eshell-mode-map [return] 'exit-minibuffer)
  (define-key eshell-mode-map [(control ?m)] 'exit-minibuffer)
  (define-key eshell-mode-map [(control ?j)] 'exit-minibuffer)
  (define-key eshell-mode-map [(meta return)] 'exit-minibuffer)
  (define-key eshell-mode-map [(meta control ?m)] 'exit-minibuffer))

;;;###autoload
(defun eshell-command (&optional command arg)
  "Execute the Eshell command string COMMAND.
With prefix ARG, insert output into the current buffer at point."
  (interactive)
  (require 'esh-cmd)
  (setq arg current-prefix-arg)
  (unwind-protect
      (let ((eshell-non-interactive-p t))
	(add-hook 'minibuffer-setup-hook 'eshell-mode)
	(add-hook 'eshell-mode-hook 'eshell-return-exits-minibuffer)
	(setq command (read-from-minibuffer "Emacs shell command: ")))
    (remove-hook 'eshell-mode-hook 'eshell-return-exits-minibuffer)
    (remove-hook 'minibuffer-setup-hook 'eshell-mode))
  (unless command
    (error "No command specified!"))
  ;; redirection into the current buffer is achieved by adding an
  ;; output redirection to the end of the command, of the form
  ;; 'COMMAND >>> #<buffer BUFFER>'.  This will not interfere with
  ;; other redirections, since multiple redirections merely cause the
  ;; output to be copied to multiple target locations
  (if arg
      (setq command
	    (concat command
		    (format " >>> #<buffer %s>"
			    (buffer-name (current-buffer))))))
  (save-excursion
    (require 'esh-mode)
    (let ((buf (set-buffer (generate-new-buffer " *eshell cmd*")))
	  (eshell-non-interactive-p t))
      (eshell-mode)
      (let* ((proc (eshell-eval-command
		    (list 'eshell-commands
			  (eshell-parse-command command))))
	     intr
	     (bufname (if (and proc (listp proc))
			  "*EShell Async Command Output*"
			(setq intr t)
			"*EShell Command Output*")))
	(if (buffer-live-p (get-buffer bufname))
	    (kill-buffer bufname))
	(rename-buffer bufname)
	;; things get a little coarse here, since the desire is to
	;; make the output as attractive as possible, with no
	;; extraneous newlines
	(when intr
	  (if (eshell-interactive-process)
	      (eshell-wait-for-process (eshell-interactive-process)))
	  (assert (not (eshell-interactive-process)))
	  (goto-char (point-max))
	  (while (and (bolp) (not (bobp)))
	    (delete-backward-char 1)))
	(assert (and buf (buffer-live-p buf)))
	(unless arg
	  (let ((len (if (not intr) 2
		       (count-lines (point-min) (point-max)))))
	    (cond
	     ((= len 0)
	      (message "(There was no command output)")
	      (kill-buffer buf))
	     ((= len 1)
	      (message (buffer-string))
	      (kill-buffer buf))
	     (t
	      (save-selected-window
		(select-window (display-buffer buf))
		(goto-char (point-min))
		;; cause the output buffer to take up as little screen
		;; real-estate as possible, if temp buffer resizing is
		;; enabled
		(and intr temp-buffer-resize-mode
		     (resize-temp-buffer-window)))))))))))

;;;###autoload
(defun eshell-command-result (command &optional status-var)
  "Execute the given Eshell COMMAND, and return the result.
The result might be any Lisp object.
If STATUS-VAR is a symbol, it will be set to the exit status of the
command.  This is the only way to determine whether the value returned
corresponding to a successful execution."
  ;; a null command produces a null, successful result
  (if (not command)
      (ignore
       (if (and status-var (symbolp status-var))
	   (set status-var 0)))
    (with-temp-buffer
      (require 'esh-mode)
      (let ((eshell-non-interactive-p t))
	(eshell-mode)
	(let ((result (eshell-do-eval
		       (list 'eshell-commands
			     (list 'eshell-command-to-value
				   (eshell-parse-command command))) t)))
	  (assert (eq (car result) 'quote))
	  (if (and status-var (symbolp status-var))
	      (set status-var eshell-last-command-status))
	  (cadr result))))))

(eshell-deftest mode simple-command-result
  "`eshell-command-result' works with a simple command."
  (= (eshell-command-result "+ 1 2") 3))

;;;_* Reporting bugs
;;
;; Since Eshell has not yet been in use by a wide audience, and since
;; the number of possible configurations is quite large, it is certain
;; that many bugs slipped past the rigors of testing it was put
;; through.  If you do encounter a bug, on any system, please report
;; it -- in addition to any particular oddities in your configuration
;; -- so that the problem may be corrected for the benefit of others.

(defconst eshell-report-bug-address "johnw@gnu.org"
  "E-mail address to send Eshell bug reports to.")

;;;###autoload
(defun eshell-report-bug (topic)
  "Report a bug in Eshell.
Prompts for the TOPIC.  Leaves you in a mail buffer.
Please include any configuration details that might be involved."
  (interactive "sBug Subject: ")
  (compose-mail eshell-report-bug-address topic)
  (goto-char (point-min))
  (re-search-forward (concat "^" (regexp-quote mail-header-separator) "$"))
  (forward-line 1)
  (let ((signature (buffer-substring (point) (point-max))))
    ;; Discourage users from writing non-English text.
    (set-buffer-multibyte nil)
    (delete-region (point) (point-max))
    (insert signature)
    (backward-char (length signature)))
  (insert "emacs-version: " (emacs-version))
  (insert "\n\nThere appears to be a bug in Eshell.\n\n"
	  "Please describe exactly what actions "
	  "triggered the bug and the precise\n"
	  "symptoms of the bug:\n\n")
  ;; This is so the user has to type something in order to send
  ;; the report easily.
  (use-local-map (nconc (make-sparse-keymap) (current-local-map))))

;;; Code:

(defun eshell-unload-all-modules ()
  "Unload all modules that were loaded by Eshell, if possible.
If the user has require'd in any of the modules, or customized a
variable with a :require tag (such as `eshell-prefer-to-shell'), it
will be impossible to unload Eshell completely without restarting
Emacs."
  ;; if the user set `eshell-prefer-to-shell' to t, but never loaded
  ;; Eshell, then `eshell-subgroups' will be unbound
  (when (fboundp 'eshell-subgroups)
    (eshell-for module (eshell-subgroups 'eshell)
      ;; this really only unloads as many modules as possible,
      ;; since other `require' references (such as by customizing
      ;; `eshell-prefer-to-shell' to a non-nil value) might make it
      ;; impossible to unload Eshell completely
      (if (featurep module)
	  (ignore-errors
	    (message "Unloading %s..." (symbol-name module))
	    (unload-feature module)
	    (message "Unloading %s...done" (symbol-name module)))))
    (message "Unloading eshell...done")))

(run-hooks 'eshell-load-hook)

;;; eshell.el ends here
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