Effective emacs - Part:1

1 Effective emacs - Part:1

emacs is very powerful and effective operating system. Ah wait did I said "operating system", Yes emacs is such a powerful editor that it runs itself as operating system. Starting from web to mail to irc to terminal to music player to coding to blogging everything you can achieve with emacs. Here I a talking about shell or terminal. There are four terminal emulator programs in emacs; shell, term, ansi-term and emacs shell (eshell).

I have worked with all of them and evaluated and I found that eshell(emacs shell) is one of the best among other. I wouldn't mind to say that its the best shell in Unix/Linux world.

1.1 Why I have chosen eshell

1. Its entirely written in lisp so I can eval and run.
2. you can use all emacs function as command prompt.

for example generate html from org or starting [[http://www.gnus.org] gnus] from command prompt

1:  10:05 AM| gnmk@:/home/gnmk $ gnus

just type "gnus", it will open buffer with gnus.

1. you can use all Linux/Unix command which are available in your box.

Please note that eshell itself has some inbuilt command like ls,cp etc.

1.2 Code snippet (from emacswiki and other website)

add below to your .emacs

1.2.1 setting up environment related variable

1:  (require 'eshell)
2:  ;; setting up environment related variable in eshell
3:  (setenv "JAVA_HOME" "/usr/local/java")
4:  (setenv "CATALINA_HOME" "/var/lib/tomcat4")
5:  (setenv "LC_ALL" "C")
6:  (setenv "PATH" "/usr/local/java/bin:/usr/local/sbin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin:/home/gnmk/bin")
7:  (setenv "LANG" "en_US.UTF8")
8:  (setenv "EDITOR" "emacsclient")

1.2.2 eshell history size and saving history while exit.

1:  (setq eshell-history-size 20000)
2:  (setq eshell-save-history-on-exit t)
3:  (setq eshell-hist-ignoredups t)
4:  (setq eshell-cmpl-cycle-completions nil)

1.2.3 scroll to the bottom

1:  (setq eshell-scroll-to-bottom-on-output t)
2:  (setq eshell-scroll-show-maximum-output t)

1.2.4 run top/ps from eshell, require term to be open

 1:  (eval-after-load 'esh-opt
 2:    '(progn
 3:       (require 'em-cmpl)
 4:       (require 'em-prompt)
 5:       (require 'em-term)
 6:       (add-hook 'eshell-mode-hook 
 7:                 '(lambda () (define-key eshell-mode-map "\C-a" 'eshell-bol)))
 8:       (add-to-list 'eshell-visual-commands "ssh")
 9:       (add-to-list 'eshell-visual-commands "tail")
10:       (add-to-list 'eshell-visual-commands "top")
11:       (add-to-list 'eshell-command-completions-alist
12:                    '("gunzip" "gz\\'"))
13:       (add-to-list 'eshell-command-completions-alist
14:                    '("tar" "\\(\\.tar|\\.tgz\\|\\.tar\\.gz\\)\\'"))
15:       (add-to-list 'eshell-output-filter-functions 'eshell-handle-ansi-color)))

1.2.5 eshell/clear function

1:  ;;from http://www.khngai.com/emacs/eshell.php
2:  (defun eshell/clear ()
3:  "04Dec2001 - sailor, to clear the eshell buffer."
4:  (interactive)
5:  (let ((inhibit-read-only t))
6:  (erase-buffer)))

1.2.6 eshell short and long prompt on request (from emacswiki)

 1:  ;; Returns the short propmpt string for eshell
 2:  (defun eshell-prompt-function-short ()
 3:    "Makes a short eshell prompt to avoid moving out of the buffer
 4:      window boundary"
 5:    (let* ((pwd (eshell/pwd))
 6:           (pwdlst (split-string pwd "/"))
 7:           (rpwdlst (reverse pwdlst))
 8:           (base (car rpwdlst)))
 9:      (concat (if (string= base "")
10:                  "/"
11:                (if (cdr pwdlst) "<...> /" ""))
12:              base
13:              (if (= (user-uid) 0) " # " " $ "))))
14:  
15:  ;; Returns the long prompt string for eshell
16:  (defun eshell-prompt-function-long ()
17:    "Makes a long standard eshell prompt"
18:    (concat (format-time-string "%l:%M %p") "| "
19:            (getenv "USER") "@" (getenv "HOSTNAME") ":"
20:            (eshell/pwd) (if (= (user-uid) 0) " # " " $ ")))
21:  
22:  (setq eshell-prompt-function
23:        'eshell-prompt-function-long)
24:  
25:  (defun eshell/sprompt ()
26:    "Makes a short eshell prompt to avoid moving out of the buffer
27:        window boundary (link to eshell-prompt-function-short)"
28:    (setq eshell-prompt-function
29:          'eshell-prompt-function-short))
30:  
31:  (defun eshell/lprompt ()
32:    "Makes a long standard eshell prompt (link to
33:        eshell-prompt-function-long)"
34:    (setq eshell-prompt-function
35:          'eshell-prompt-function-long))

1.2.7 find file when use emacs as one of the command

1:  (defun eshell/emacs (file)
2:  "find-file alias"
3:    (find-file file))

1.2.8 find file when use w3m

1:  (defun eshell/w3m (file)
2:  "w3m-find-file alias"
3:    (w3m-find-file file))

1.2.9 info command

1:  (defun eshell/info ()
2:    "info alias"
3:    (info))

1.2.10 display emacs manual when type einfo

1:  (defun eshell/einfo ()
2:    "Display emacs manual"
3:    (info-emacs-manual))

1.2.11 aliase

1:  (defun eshell/ll (&rest args)
2:    "ls -alh alias"
3:    (eshell/ls "-alh" args))
4:  
5:  (defun eshell/la (&rest args)
6:    "ls -a alias"
7:    (eshell/ls "-a" args))

1.2.12 convert ansi color faces in eshell

 1:  ;; This will transform ansi color to faces in Emacs shell!
 2:  (ansi-color-for-comint-mode-on)
 3:  (defun eshell-handle-ansi-color ()
 4:    (ansi-color-apply-on-region eshell-last-output-start
 5:                                eshell-last-output-end))
 6:  (add-hook 'eshell-mode-hook
 7:            '(lambda ()
 8:               (add-to-list
 9:                'eshell-output-filter-functions
10:                'eshell-handle-ansi-color)))

1.2.13 compile process in background

 1:  ;;Here’s how to compile in the background, also by Kai.
 2:  (defun eshell/ec (&rest args)
 3:    "Use `compile' to do background makes."
 4:    (if (eshell-interactive-output-p)
 5:        (let ((compilation-process-setup-function
 6:               (list 'lambda nil
 7:                     (list 'setq 'process-environment
 8:                           (list 'quote (eshell-copy-environment))))))
 9:          (compile (eshell-flatten-and-stringify args))
10:          (pop-to-buffer compilation-last-buffer))
11:      (throw 'eshell-replace-command
12:             (let ((l (eshell-stringify-list (eshell-flatten-list args))))
13:               (eshell-parse-command (car l) (cdr l))))))
14:  (put 'eshell/ec 'eshell-no-numeric-conversions t)

Type ec <command> from eshll prompt will open another buffer with command output/status.