Effective spell check in Emacs

CREATED: <2014-01-21>

UPDATED: <2016-12-07 Wed>

I use Flyspell in web-mode. But the solution works in other major modes.

I assume you already turn on flyspell for all the programming languages by inserting below code into .emacs,

(add-hook 'prog-mode-hook 'flyspell-prog-mode)

There is also a short tutorial on:

  • How to setup flyspell
  • Difference between hunspell and aspell
  • How to setup hunspell

1 Spell check in HTML

I will check,

  • Text between html tag like <label>Please input email</label>
  • Value of html input control like <input type"text" value="Please input your name">=
  • CSS class name like <div class"btn btn-default" />=

My setup:

;; {{ flyspell setup for web-mode
(defun web-mode-flyspell-verify ()
  (let* ((f (get-text-property (- (point) 1) 'face))
     ;; Check the words with these font faces, possibly.
     ;; this *blacklist* will be tweaked in next condition
     ((not (memq f '(web-mode-html-attr-value-face
                     web-mode-comment-face ;; focus on get html label right
      (setq rlt t))
     ;; check attribute value under certain conditions
     ((memq f '(web-mode-html-attr-value-face))
        (search-backward-regexp "=['\"]" (line-beginning-position) t)
        (setq rlt (string-match "^\\(value\\|class\\|ng[A-Za-z0-9-]*\\)$"
                                (thing-at-point 'symbol)))))
     ;; finalize the blacklist
      (setq rlt nil)))
(put 'web-mode 'flyspell-mode-predicate 'web-mode-flyspell-verify)
;; }}

I use web-mode for HTML files. The technique applies on other modes (php-mode, html-mode ….) .

2 Don't display doublon (double word) as error

Modern CSS frameworks like Bootstrap make doublon unavoidable. For example, CSS class name btn btn-default contains double word btn.

So we need stop displaying doublon as error in HTML,

(defvar flyspell-check-doublon t
  "Check doublon (double word) when calling `flyspell-highlight-incorrect-region'.")
 (make-variable-buffer-local 'flyspell-check-doublon)

(defadvice flyspell-highlight-incorrect-region (around flyspell-highlight-incorrect-region-hack activate)
  (if (or flyspell-check-doublon (not (eq 'doublon (ad-get-arg 2))))

(defun web-mode-hook-setup ()
  (flyspell-mode 1)
  (setq flyspell-check-doublon nil))

(add-hook 'web-mode-hook 'web-mode-hook-setup)

3 Spell check camel case strings

We can check camel cased string/variable/function if and only if aspell is used.

Insert below code into .emacs,

;; if (aspell installed) { use aspell}
;; else if (hunspell installed) { use hunspell }
;; whatever spell checker I use, I always use English dictionary
;; I prefer use aspell because:
;; 1. aspell is older
;; 2. looks Kevin Atkinson still get some road map for aspell:
;; @see http://lists.gnu.org/archive/html/aspell-announce/2011-09/msg00000.html
(setq ispell-program-name "aspell"
      ;; force the English dictionary, support Camel Case spelling check (tested with aspell 0.6)
      ispell-extra-args '("--sug-mode=ultra" "--lang=en_US" "--run-together" "--run-together-limit=5" "--run-together-min=2"))

Please note the option --run-together-min=2 means the minimum length of each sub-word extracted from camel case string is two. Please run man aspell in shell for details.

4 Summary

EmacsWiki suggests (flyspell-prog-mode) which only checks typo in comments.

But as I proved, Emacs gives you full freedom to design a different solution.

Screen shot (typos are underscored):


5 Javascript and ReactJS setup (OPTIONAL)

If you fully understand my previous sections, you don't need read this section.

Insert below code into .emacs,

(defun js-flyspell-verify ()
  (let* ((f (get-text-property (- (point) 1) 'face)))
    ;; *whitelist*
    ;; only words with following font face will be checked
    (memq f '(js2-function-call
(put 'js2-mode 'flyspell-mode-predicate 'js-flyspell-verify)
(put 'rjsx-mode 'flyspell-mode-predicate 'js-flyspell-verify)

How to execute user program for System V init script

Memo for my self.

sudo ls -1 /etc/{rc,init}.d/|grep local

# then read the file either rc.local or local

Notes on Google Chrome's dev tool

command in source panel hotkey
Continue C-\
Toggle break point C-B
Step over C-'
Step into C-;
Step out S-C-;
Up call stack C-,
Down call stack C-.
Toggle console view ESC
Goto line C-G
Goto file C-P
Jump to method S-C-O
  • I don't use hotkey F1~F12 because my windows manager is different from most developers
  • live editing does not work on Chromium 30.0.1599.114 Built on Ubuntu 13.04. Anyway, I don't need this functionality
  • hotkeys of "Continue" button in Sources panel does not work on Chromium 30.0.1599.114 Built on Ubuntu 13.04.
  • "Break on" inspected element is extremely useful

My grub2 configuration


!/bin/sh -e

echo "# Adding Windows GRUB 2 menu"

cat &lt;&lt; EOF

menuentry "Windows XP" {


insmod chain

insmod ntfs

set root=(hd0,1)

chainloader +1




Copyright 1999-2013 Gentoo Foundation

Distributed under the terms of the GNU General Public License v2

$Header: /var/cvsroot/gentoo-x86/sys-boot/grub/files/grub.default-2,v 1.4 2013/09/21 18:10:55 floppym Exp $

To populate all changes in this file you need to regenerate your

grub configuration file afterwards:

'grub2-mkconfig -o /boot/grub/grub.cfg'

See the grub info page for documentation on possible variables and

their associated values.







Append parameters to the linux kernel command line


Append parameters to the linux kernel command line for non-recovery entries


Uncomment to disable graphical terminal (grub-pc only)


The resolution used on graphical terminal.

Note that you can use only modes which your graphic card supports via VBE.

You can see them in real GRUB with the command `vbeinfo'.


Path to theme spec txt file.

The starfield is by default provided with use truetype.

NOTE: when enabling custom theme, ensure you have required font/etc.


Background image used on graphical terminal.

Can be in various bitmap formats.


Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to kernel


Uncomment to disable generation of recovery mode menu entries


Why Emacs is better editor - a case study for javascript developer

UPDATED: 2014-01-15 Wed

Let's see an example in real life development.


For people who does not get the key points of this article, here are the points:

  • Emacs has an embedded javascript interpreter which I extend a little bit.
  • Other editors just use external tools or regular expression to do the semantic analysis.
  • The difference of above two is bigger than the difference between machine gun and spear.


I'm maintaining a big javascript file with thousands of lines of legacy code.

My most urgent issue is how to list all the functions in that javascript file and jump to the definition of specific function easily.

The modern enterprise application usually define the javascript function in some complex data structure. So most editors are not good at listing the functions.

To understand what "complex" means, let's check some code from real world application:

    ignore: " :hidden",
    rules : {
        password : {
            required : function () { return $(el.password).is(":visible"); }
        accountNumber : {
            required : function () {
                return $(el.accountNumber).is(":visible");
            digits : true
        // ... I skipped next 200 lines which are similar to above lines

    messages : {
        password: {
            required : "Please input a valid password"
        accountNumber: {
            required : "Please provide a valid account number",
            digits : "Please enter only digits",
        // ... I skipped next 200 lines which are similar to above lines

Most editors like Sublime Text 3 cannot display the javascript functions with meaningful context in this case. All you can see is only a bunch of functions with name "required".: http://blog.binchen.org/wp-content/uploads/2013/12/wpid-sublime-functions.png


Emacs has a js2-mode which is basically a javascript interpreter written in lisp. It's created by Steve Yegge and now maintained by mooz.

Since js2-mode is a interpreter, basically it can do anythig you want. The key point is to understand the Abstract Syntax Tree (AST) defined in js2-mode.

I already submitted the patch to mooz so everyone will enjoy this feature in the future.

Here is the screen shot of emacs in old js2-mode, the UI is based on Imenu Mode and helm: http://blog.binchen.org/wp-content/uploads/2013/12/wpid-emacs-functions.png

The screen shot after we applying the above patch: http://blog.binchen.org/wp-content/uploads/2013/12/wpid-emacs-functions-improved.png


That's an example of beauty of Emacs.

It gives you freedom and power. You can base your work on the top geeks like Steve Yegge and mooz. Just a few lines of lisp code to kick ass.


My patch is incorporated into js2-mode since version 20140114. You can install it through emacs package manager.

After installing js2-mode, you need paste only one line code into your ~/.emacs to enable the feature:


The UI to display the candidate in this actile is from package helm. But there are many other UI front end for imenu instead of helm.

The helm version should be 20140125.1101 or higher, you can install helm from melpa.

After installing helm, you can use command "M-x helm-imenu" to show the list of functions to jump to. Here is the screen shot how I use imenu in my hello2.js:


Why some systemd service on ArchLinux does not work

List failed services

sudo systemctl --failed

I can also use sudo journalctl -b to get the log message when booting all the services. But not very useful.

Find the root cause of failed service

sudo systemctl status service-name

Why my /usr/lib/systemd/system/network-wifi.service does not work

Here is the content of my wifi service


Description=Wireless networkd connectivity (wlan0)









ExecStart=/usr/bin/ip link set wlan0 up

ExecStart=/usr/bin/wpa_supplicant -B -i wlan0 -c /etc/wpa_supplicant/yang.conf

ExecStart=/usr/bin/dhcpcd wlan0

ExecStop=/usr/bin/ip addr flush dev wlan0

ExecStop=/usr/bin/ip link set dev wlan0 down



It's because netcfg.service blocks my network-wifi.service.

Solutin is simple:

sudo systemctl disable netcfg

How to start a service as as specific user (mpd, for example)

This is the content of /usr/lib/systemd/system/mpd.service:


Description=Music Player Daemon

After=network.target sound.target


ExecStart=/usr/bin/mpd --no-daemon /home/cb/.mpd/config





  • 菜谱
  • 油炸蒜末,倒入蚝油(至少4大勺)搅拌,最后放入生菜(半颗),搅拌一下即可,可以最后放盐如果嫌不咸的话
  • 生菜用开水烫过沥干,因为其容易出水
  • 不要放糖,蚝油本身有甜味了





2.1. 利用香菇去做燴的動作,讓一些物料巴在上頭

2.2. 不要加雞精粉跟糖,蠔油已經有甜度了。

2.3. 蠔油跟豬油一起拌會更香



2.起鍋下1茶匙油,爆香香菇片,下蠔油拌炒〈炒過的蠔油有焦糖味在裡面, 味道會更香〉,加入自來高湯〈自來高湯的量,只要抓蠔油鹹度即可〉,小滾一會兒, 讓香菇的甜味煮出來。

3.調太白粉水〈粉1:水3〉,加入適量的太白粉水,加入少許香油,不需攪拌,熄火 〈澱粉會吃油,攪拌的話會膨脹變成一團糊〉。

4.在滾水鍋中加鹽,汆燙西生菜〈菜要最後汆燙〉,加入少許薑末〈薑汁也行,薑可提味,巴在葉片上會更好吃〉汆燙,撈起西生菜瀝乾水份〈因為西生菜很會出水, 一定要徹底瀝乾水份,否則會水水的〉。



Screen shot: http://blog.binchen.org/wp-content/uploads/2013/11/wpid-fried-cabbage.jpg

Memo on upgrading ArchLinux

shit happens

pacman -Syu

archlinux replace grub with grub2

I cannot install grub2, blocklists stuff

downgrade to grub-obsolete

then grub

setup (hd0) to install MBR

restart netbook (make sure the boot priority is right)

notes on upgrading Gentoo Linux

sudo emerge --update --deep --with-bdeps=y --newuse world

  • I get notified that some newer version package is required, so I have to manually install those package and re-run the emerge world
  • Some package is gone (libreoffice-bin, for example).

Here is command to manually install package:

sudo ebuild /usr/portage/www-client/firefox-bin/firefox-bin-23.0.ebuild unpack compile install qmerge clean

How to take screen shot for business people efficiently in Emacs

CREATED: <2013-10-23 Wed>

UPDATED: <2015-08-11 Tue>

1 Tools

Name Description Minimum version
Org-mode create org-file which could be converted to odt file 7.8
scrot command line tool to take screen shot any version
Libreoffice convert odt to Microsoft Word any version
xsel X clipboard tool any version

2 Work flow

2.1 Use scrot to screenshot and put its path into clipboard

scrot '%H%M%S-%d_$wx$h.png' -e 'mkdir -p ~/screenshot;mv $f ~/screenshot/;echo ~/screenshot/$f|tr -d \"\\n\"|xsel -ib;'

2.2 Create org file and insert path of screen shot

Actually I use below elisp command to do the insertion for me.

(defun insert-file-link-from-clipboard ()
  "Make sure the full path of file exist in clipboard. This command will convert
The full path into relative path and insert it as a local file link in org-mode"
  (let (str)
        ((eq system-type 'cygwin) "getclip")
        ((eq system-type 'darwin) "pbpaste")
        (t "xsel -ob"))
      (setq str (buffer-string)))

    ;; convert to relative path (relative to current buffer) if possible
    (let ((m (string-match (file-name-directory (buffer-file-name)) str) ))
      (when m
        (if (= 0 m )
            (setq str (substring str (length (file-name-directory (buffer-file-name)))))
        (insert (format "[[file:%s]]" str)))

2.3 Convert org file into Microsoft Word format

I'm sure this method works even on Windows. But I don't have Windows PC to validate my belief. Libreoffice is required.

Run the command "M-x org-export-as-odt".

Word document is automatically created if you insert below code into your ~/.emacs:

;; This setup is tested on Emacs 24.3 & Emacs 24.4 on Linux/OSX
;; org v7 bundled with Emacs 24.3
(setq org-export-odt-preferred-output-format "doc")
;; org v8 bundled with Emacs 24.4
(setq org-odt-preferred-output-format "doc")
;; BTW, you can assign "pdf" in above variables if you prefer PDF format

;; Only OSX need below setup
(defun my-setup-odt-org-convert-process ()
  (let ((cmd "/Applications/LibreOffice.app/Contents/MacOS/soffice"))
    (when (and (eq system-type 'darwin) (file-exists-p cmd))
      ;; org v7
      (setq org-export-odt-convert-processes '(("LibreOffice" "/Applications/LibreOffice.app/Contents/MacOS/soffice --headless --convert-to %f%x --outdir %d %i")))
      ;; org v8
      (setq org-odt-convert-processes '(("LibreOffice" "/Applications/LibreOffice.app/Contents/MacOS/soffice --headless --convert-to %f%x --outdir %d %i"))))

Emacs will find the binary "soffice" from libreoffice to do the conversion.

2.4 Tips

If you need page break in exported document, insert below snippet into the org file:

#+ODT: <text:p text:style-name="PageBreak"/>