2.emacs show line numbers
M-x linum-mode (or global-linum-mode), and put (global-linum-mode t) in your ~/.emacs (or ~/.emacs.d/init.el) to enable it at startup.
linum: separating line numbers from text
find this pice of code in linum.el: (setq width (max with (length str)))
change to (setq width (max width (+ (length str) 1)))
conctol the line number format: (setq linum-format "%3d")
set on for appointed mode:
(setq linum-mode-inhibit-modes-list '(eshell-mode
                                      shell-mode
                                      erc-mode
                                      jabber-roster-mode
                                      jabber-chat-mode
                                      gnus-group-mode
                                      gnus-summary-mode
                                      gnus-article-mode))

(defadvice linum-on (around linum-on-inhibit-for-modes)
  "Stop the load of linum-mode for some major modes."
    (unless (member major-mode linum-mode-inhibit-modes-list)
      ad-do-it))

(ad-activate 'linum-on)
compile .el to .elc: atl+x byte-compile-file
http://www.emacswiki.org/emacs/LineNumbers

3.using gzip - compress/uncompress file
compress: gzip [file name]
uncompress: gunzip [file name]
keep the input file: gunzip [file.gz] -c >> [file]
gunzip/gzip -c which simply writes the output stream to stdout
compress all the files under a director: -r
http://blog.csdn.net/yuyongpeng/article/details/1818717

4.emacs do not auto save backup files
(setq auto-save-default nil)

5.emacs close file ctrl+x k