Haifeng's Technical Blog

How to setup spell checking for Kile editor

2011-05-22T06:16:00.000-07:00

Spell checking in Kile will be very useful. Here is one way to setup it.

Install aspell

sudo apt-get install aspell aspell-en dictionaries-common hunspell-en-us

Goto Applications->Other->Spell Check
In the client, choose Aspell.
Restart Kile.

You can open the file

~/.aspell.en.pws

It stores the local dictionary for the spell checking.

How to install and upgrade package in Ubuntu

2011-02-22T04:52:00.000-08:00

Edit


vi /etc/apt/sources.list


deb http://ppa.launchpad.net/chromium-daily/ppa/ubuntu karmic main
deb-src http://ppa.launchpad.net/chromium-daily/ppa/ubuntu karmic main


sudo apt-get update
sudo apt-get install chromium-browser


sudo apt-get upgrade

Make a standalone plot using TikZ

2011-02-11T14:01:00.000-08:00


\documentclass{minimal}

\usepackage{tikz}

\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{5pt}%


\begin{document}

\begin{tikzpicture}[scale=1.6]
    \draw[->] (0,0) -- (4,0) coordinate (x axis);
    \draw[->] (0,0) -- (0,3.5) coordinate (y axis);
  \shadedraw [shading=axis,shading angle=90, left color=blue!70,right color=blue!30, draw=blue!50!black] (0.2,0) rectangle (3.8,3.3);
    \shadedraw [shading=axis,shading angle=90] (0.6,0) rectangle (2.0,2.3);
 
 \node at(0.2,-0.2){{$20$}};
 \node at(0.6,-0.2){{$60$}};
 \node at(2.0, -0.2){{$600$}};
 \node at(3.8, -0.2){{$1400$}};
 \node at(4.5, 0){{$p_{T}$[GeV]}};

 \node at(-0.2, 2.3){{$2.8$}};
 \node at(-0.2, 3.3){{$4.4$}};
 \node at(-0.2, 3.7){{$|y|$}};

 %
 \node at(1.3, 1.3){{$17\,\,nb^{-1}$}};
 \node at(2.9, 2.6){{$40\,\,pb^{-1}$}};
    \end{tikzpicture}

\end{document}

Merge several EPS files to one file

2011-02-09T04:02:00.001-08:00


gs -sDEVICE=epswrite     -dNOPAUSE -dBATCH -dSAFER     -sOutputFile=merged.eps   *eps

Merge EPS and convert EPS to PDF


gs -sDEVICE=pdfwrite     -dNOPAUSE -dBATCH -dSAFER     -sOutputFile=merged.pdf  *eps

http://www.linuxjournal.com/content/tech-tip-using-ghostscript-convert-and-combine-files

The best way to concert a bunch of eps file to a combined pdf file is,


for i in `ls *eps`
do
    ps2pdf -dEPSCrop ${i}
done


gs -sDEVICE=pdfwrite     -dNOPAUSE -dBATCH -dSAFER     -sOutputFile=merged.pdf  *pdf

How to update TikZ library

2010-09-26T01:58:00.000-07:00

Sometime you need to update your TikZ library to contain new library files. Then you can do like this,

Go to TikZ Build to find out the latest built version for TikZ.

Download the tar package and extract it to some temporary place.


ls pgfCVS2010-07-25_TDS.zip
mkdir pgfInstallFile
unzip pgfCVS2010-07-25_TDS.zip -d pgfInstallFile/
doc/ tex/

Go to /usr/share/texmf/tex/

You have to replace the old pgf package file with the new file. You can copy


cp -r $pgfInstallFile/tex/context/pgf/  /usr/share/texmf/tex/context/pgf/  ;
cp -r $pgfInstallFile/tex/generic/pgf/  /usr/share/texmf/tex/generic/pgf/  ;
cp -r $pgfInstallFile/tex/latex/pgf/    /usr/share/texmf/tex/latex/pgf/  ;
cp -r $pgfInstallFile/tex/plain/pgf/    /usr/share/texmf/tex/plain/pgf/  ;

After that, you can update the tex file configuration,
```
texhash ;
```

Install a Latex style file on Linux

2010-07-22T06:41:00.000-07:00

Take bbding as an example.


$ wget http://www.tug.org/texlive/Contents/live/texmf-dist/tex/latex/bbding/bbding.sty # Get the style file from web site.
$ mkdir /usr/share/texmf/tex/latex/bbding # Make a directory for bbding
$ cp bbding.sty  /usr/share/texmf/tex/latex/bbding  # Copy bbding style file to this directory.
$ texhash  # Update linux configuration

Tips for Latex usage

2010-03-21T04:51:00.000-07:00

Tips and tricks for Latex
(TeX, LaTeX, BibTeX and friends, are a constant source of joy and frustration. This growing collection of tips and tricks is an attempt to document some of the things I have learned working with these wonderful tools. This page is just one of many similar LaTeX tips and tricks pages on the net. Hopefully you'll find something useful here.)

How to prevent memory leak in C plusplus

2010-03-08T08:56:00.000-08:00

'delete' all variables defined by 'new'
Unless you know what you are doing, you have to delete any variables which are defined by 'new'. so that you free the same memory you allocated.
```
char* str = new char [30];
delete [] str;
```
Watch those pointer assignments
Every dynamic variable (allocated memory on the heap) needs to be associated with a pointer. When a dynamic variable becomes disassociated from its pointer(s), it becomes impossible to erase. Again, this results in a memory leak.
```
char* str1 = new char [30];
char* str2 = new char [40];
strcpy(str1, "Memory leak");
str2 = str1; // Bad! Now the 40 bytes are impossible to free.
delete [] str2; // This deletes the 30 bytes.
delete [] str1; // Possible access violation.
```
Be careful with local pointers
A pointer you declare in a function is allocated on the stack, but the dynamic variable it points to is allocated on the heap. If you don't delete it, it will persist after the program exits from the function.
```
void Leak(int x){
char* p = new char [x];
// delete [] p; // Remove the first comment marking to correct.
}
```
Pay attention to the square braces after "delete"
Use "delete" by itself to free a single object. Use "delete" [] with square brackets to free a heap array. Don't do something like this
```
char* one = new char;
delete [] one; // Wrong
char* many = new char [30];
delete many; // Wrong!
```

Learning Cpp -- When to use 'new' -- Stack or Heap

2010-03-08T07:51:00.000-08:00

Use new to define large large chunks of dataMore typically, you use new with larger chunks of data, such as arrays, strings, and structures. This is where new is useful. Suppose, for ample, you’re writing a program that might or might not need an array, ending on information given to the program while it is running. If you create an array by declaring it, the space is allocated when the program is compiled. Whether or not the program finally uses the array, the array is there, using up memory. Allocating the array during compile time is called static binding, meaning that the array is built in to the program at compile time. But with new, you can create an array during runtime if you need it and skip creating the array if you don’t need it.Or you can select an array size after the program is running. This is called dynamic binding, meaning that the array is created while the program is running. Such an array is called a dynamic array. With static binding, you must specify the array size when you write the program. With dynamic binding, the program can decide on an array size while the program runs.

use .emacs to configure emacs

2010-03-04T14:51:00.000-08:00

My .emacs file


(setq frame-title-format
     (concat  "%b - emacs@" (system-name)))

;; default to unified diffs
(setq diff-switches "-u")

;; always end a file with a newline
(setq require-final-newline nil)

;;(put 'set-goal-column 'disabled nil)
;; ====================
(setq inhibit-default-init t)
(setq inhibit-startup-message t)

(custom-set-variables
 ;; custom-set-variables was added by Custom -- don't edit or cut/paste it!
 ;; Your init file should contain only one such instance.
'(auto-compression-mode t nil (jka-compr))
'(case-fold-search t)
'(current-language-environment "UTF-8")
'(default-input-method "rfc1345")
'(global-font-lock-mode t nil (font-lock)))

(when window-system
  ;; enable wheelmouse support by default
  (mwheel-install)
  ;; make switching frames works properly under the default click-to-focus
  (setq focus-follows-mouse nil))

use Xdefaults to configure emacs

2010-03-04T14:39:00.000-08:00

Create a new .Xdefaults file in your home directory. This file can be used to configure your emacs.


Emacs.Font: fontset-courier
Emacs.Fontset-0:-*-courier-medium-r-normal-*-18-*-*-*-*-*-fontset-courier,\
emacs.geometry:90x60+200+200
emacsp.background:gray75

Emacs.foreground:  gray
Emacs.background:  black

Then you can do this to make it work.
```
xrdb .Xdefaults
```

How to add syntax highlighting to Blogger

2009-10-14T14:01:00.000-07:00

For this topic, I have found some excellent bloggers.

Add syntax highlighting.

gdb debugger introduction

2009-08-25T02:54:00.000-07:00

Compile your program using debug. If you want to use gdb, you have to compile your code using '-g' flag. It will tell the compiler to store the debug information in object file. It describes the data type of each variable or function.
```
g++ -g test.cxx -o test
```

Run your program.
```
gdb test
```
Quit your program.
```
quit ;  or  Ctrl + D
```

Set up break points.


> b 19  // break at line 19 at a file
> b func1 // break at func1
> b testClass::testFunc(int) //  C++ is polymorphic. you must tell break which version of the function you want to break on
> info breakpoints  // can print out all the break points

Use backtrace.


backtrace

You can see many frames related the point.


#0  std::string::assign (this=0xd3d704c, __str=@0xfd0d05)
#1  0x00e4e524 in std::string::operator= (this=0xd3d704c, __str=@0xfd0d05)
#2  0x065692d4 in IssueSeverity (this=0xd3d7048, rhs=@0xfd0d01)
#3  0x0656831f in StatusCode::cloneSeverity (sev=0xfd0d01) at ../src/Lib/StatusCode.cpp:28
#4  0x0317eb29 in StatusCode (this=0xbff07888, rhs=@0xbff077a4)
#5  0xb7947250 in ?? ()
#6  0xbff07888 in ?? ()
#7  0xbff077a4 in ?? ()
#8  0x00000000 in ?? ()

You can take a look at the detail of one frame.


frame 1
info frame
info locals
info args

links

Gmail : How to mark all the unread email to read

2009-08-13T11:18:00.000-07:00

Maybe you have many emails you don't care. So you just want to mark these emails to read and don't want to read them. In Gmail, if you just click the button "unread" at the top of mail, it will just select the unread email in this page(less than 50 conversation). You have to go to next page to select unread and mark as read. That is not convenient. What you can do is to type"is:unread" in search email frame.

Then you can see all the unread emails(not in one page). Now you can click "select All". In this case, you just select the unread emails in one page. Gmail will ask you whether you want to select all the unread emails. You choose yes. Then all your unread emails have been selected. The last step is click mark as read.

Type"is:unread" in search email frame.
Select All
Gmail will ask you whether you want to select all the unread emails. You choose yes.
Click "Mark as read".

xterm

2009-08-10T15:16:00.001-07:00

If you use xmanager, maybe you need this setting to make your terminal look better.


/usr/bin/X11/xterm   -bg black -fg gray  -fn  10x20   +cm +dc   -ls -display $DISPLAY

Cpp : My Test

2009-07-19T07:41:00.000-07:00

Integer
If you use integer in C++, you should be careful. Because the integer width is limited. For example, an short int in Cpp is 16bits. An int is no shorter than short integer. A long integer is 32 bits. I just do a test on i686 GNU/Linux. Here is the result.


short  a ;
> a^14 = 16384
> a^15 = -32768
> a^16 = 0


int  a ;
> a^30 = 1073741824
> a^31 = -2147483648
> a^32 = 0


long a ;
> a^30 = 1073741824
> a^31 = -2147483648
> a^32 = 0


unsigned short a ;
> a^14 = 16384
> a^15 = 32768
> a^16 = 0


unsigned int a ;
> a^30 = 1073741824
> a^31 = 2147483648
> a^32 = 0


unsigned long a ;
> a^30 = 1073741824
> a^31 = 2147483648
> a^32 = 0

Cron on Linux

2009-05-12T08:21:00.000-07:00

If you have many scripts running on a server machine(I have 6 scripts running on different machines). These scripts can be monitoring script or something important to the system. But sometime these script can crash due to some unknown reasons. At this time it's very dangerous to the system. So setting up one mechanism to monitor the condition of these scripts is very important to the system and your work. The CRON job can do this job. CRON is part of Linux and can be used to run a script at some time you want. You can use this to open the cron job setting.


crontab -e

Add this to this file.


*/5 * * * * /usr/local/bin/mcJobMonitor.py >> /dev/null

If you want to know the meaning of this sentence, please go to Cron on Linux.
This mcJobMonitor.py is

#!/usr/bin/python
#//////////////////////////////////////////////////
#  Haifeng Li
#///////////////////////////////////////////////////

import sys, os, time, commands, getopt

def SendMailtoUser(ScriptName ):

hostname = commands.getoutput("uname -n")
timedate = commands.getoutput("date")
pwd      = commands.getoutput("pwd")
message = "Your script "+ScriptName+" in machine " +hostname+ " is dead.   \n"\
         +"We have restarted this script. You can go to this machine to check the reason.  \n"
email    = "xxxxxxx@gmail.com"
command  ="".join(["echo \"", message, \
                "\" | mail ", email, "  -s \"Cron Monitor for  ", ScriptName, "\""])
os.system(command)

if __name__=="__main__" :

#________________________updatedatabase.py________________________________
ScriptName = "/var/www/html/hpeng3/script/updatedatabase.py"
status = commands.getoutput("ps -ef | grep 'updatedatabase.py' | grep -v grep")
status = status.strip()
if status == '' :
   pushd     =  "pushd  /var/www/html/hpeng3/script"
   restart   =  "./restart.sh"
   popd      =  "popd"
   command   = ";".join([pushd, restart, popd])
   os.system(command)
   SendMailtoUser(ScriptName )

Beamer Usage

2009-05-04T09:59:00.001-07:00

Initial process of Linux

2009-04-20T01:53:00.000-07:00

Suppose you set up a sever or a administration machine, where there are many monitoring programs. If the machine reboots, then you have to restart all the programs manually. Maybe sometime you forget some processes. In that case, it's very danger to the system. So you should set up some initialization of Linux system. When the machine reboot, some processes will start automatically. This is what I have done.


emacs -nw /etc/rc.d/rc.local

You will see.


#!/bin/sh
#
# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.
touch /var/lock/subsys/local
/usr/sbin/ntpdate ntp1.cs.wisc.edu
# define by Haifeng Li.  For the CHTC machine's jobs scanning
/home/haifeng/chtcKillZombieJobs.py >> /home/haifeng/chtcKillZombieJobs.log &
# For the removing the old directory.
/home/hpeng/chtcclean.py  >>  /home/hpeng/chtcclean.log &

-----------------------------------------------------------------------------------------------------
Linux Process Control
Linux start scripts

Static library and dynamic library in Linux

2009-04-17T05:16:00.000-07:00

A library is a package of code which can be used by other program. First, libraries are compiled. You don't have to compile them when you are using them. Second, because the complied libraries are in machine language, it can prevent other people to know the source code. This is important for business use. But it's not good for open source.
-----------------------------------------------------------------------------------------------------
What is library

Actually, library is just a collection of header(C++) files or sub functions(maybe Fortran).

There are two types library.

Static library(archive library). In linux, statics lib has a .a extension. When you compile a program using static library, the program will copy all the funcitonally to the program. So your executable file is very big. One advantage of static library is the program does not have to find the lib when it's running. This is very convenient when you compile the code in one machine and run the program in another machine and you don't want to install the lib in that machine.
Dynamic library(shared library). Dynamic library has a .so extension in Linux. Dynamic lib will be linked when the program is running. So you don't have to copy all the libs to your executable file. That is a advantage. Because the library you are using may be very big(GB).

------------------------------------------------------------------------------------------------------
Generate library

To create a static library,
```
ar rcs my_library.a file1.o file2.o
```
This command adds the objects files file1.o and file2.o to the static library.
Create a Shared library. First , create the object files using the gcc -fPIC of -fpic flag. The -fPIC and -fpic option enable 'position independent code' generation. Here is an example.
```
gcc -fPIC -g -c -Wall a.c
gcc -fPIC -g -c -Wall b.c
gcc -shared -Wl,-soname,libmystuff.so.1  -o libmystuff.so.1.0.1 a.o b.o -lc
```
-g means debugging information. -Wall will generate warnings. -c is compilation.

--------------------------------------------------------------------------------------------------------
Use Library

If you want to use the shared library, you have to tell the computer where the library is. Actually you have to how the Linux system to find lib.

Default shared lib directory. The default dir is /usr/lib, which means the system will first search the libs in /usr/lib. Then you have to run ldconfig.
```
ldconfig -n directory_with_shared_libraries
```
You can use LD_LIBRARY_PATH to tell the system to find the shared libraries before the usual places.
```
LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH  my_program
```

ldd can display the dependence of a shared library.


ldd /usr/bin/mesg

It will display


 libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7eaf000)
  /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0xb7feb000)

---------------------------------------------------------------------------------------------------------
My Makefile

This is a Makefile I am using.


##################################
# root variables
ROOTCFLAGS   := $(shell root-config --cflags)
ROOTLIBS     := $(shell root-config --libs) -lRooFit -lHtml -lCore -lCint -ldl -lTree \
-lGpad -lGraf -lHist -lMatrix -lPostscript -lMinuit -lMinuit2 -lPhysics
# Programs
CXX          = g++
F77          = f77
CXXFLAGS     = -g -ggdb -Wall -fPIC -Wno-deprecated
MY_CXXFLAGS  = -static
LDFLAGS      = -g
SOFLAGS      = -shared
# do yourself a favor, use gcc for linking, and not ld
LD           = CXX
# local Includes
INCDIR       = -Iinclude
# Assign or Add variables
CXXFLAGS    += $(ROOTCFLAGS)
CXXFLAGS    += $(INCDIR)
# Assigan or add variables
LIBS        += $(ROOTLIBS)
validation: src/validation.C clean
$(CXX) $(CXXFLAGS) $(MY_CXXFLAGS) -c  src/validation.C -o lib/validation.o
$(CXX) lib/validation.o -o bin/validation $(LDFLAGS) $(LIBS)
clean:
rm -rf bin/* lib/*

$(shell root-config --libs) is a fantastic bash command. When you run the executable file, this command will be evaluated and will give the all the libs related to root(which is a analysis framework of high energy physic). In my case, the result of this command is


-L/afs/cern.ch/sw/lcg/external/root/5.18.00/slc4_ia32_gcc34/root/lib -lCore -lCint -lRIO -lNet -lHist -lGraf -lGraf3d -lGpad -lTree -lRint -lPostscript -lMatrix -lPhysics -pthread -lm -ldl -rdynamic

--------------------------------------------------------------------------------------------
Program Library HOW TO
Static and Dynamic Libraries
Analysis of static and shared library
Programming of static and shared library

Page Size in ps2pdf

2009-04-16T12:57:00.000-07:00

ps2pdf is a linux tool, which can convert ps(or eps) file to pdf file. If you convert a ps file to a pdf, the default page size is letter. Some time you want to get different size plots. You can use


ps2pdf  -dEPSCrop  jet.eps

Or you can use epstopdf


epstopdf muonDetail.eps

This command is working only for eps file, which has a bounding box. If you open a ps file, you can see the


%!PS-Adobe-2.0 EPSF-2.0
%%BoundingBox:  0 0 567 552

There is no bounding box in ps file. So you can not get the special size pdf file from a ps file.

You also can use ps2eps to convert ps file to eps. This program will calculate the boundary box for ps file and generate new eps file with a boundary box.


ps2eps electron.ps

PostScript-to-PDF converter

Image manipulation using Python

2009-04-14T12:31:00.000-07:00

You can use Python Image model to manipulate the image. It's interesting because you know that many pixels compose a picture. And the pixels are in different mode. For example, RGB. This is a python script which can print a new image.


#!/usr/bin/python

import sys
import Image, ImageDraw

newpic = Image.new("RGB", (300,300), color=(255,255,255))

xsize, ysize = newpic.size

for x in xrange(xsize) :
for y in xrange(ysize) :
newpic.putpixel((x,y), (int(255*(y/ysize)), int(255*x*y/(xsize*ysize)), int(255*(x/xsize))))


newpic.show()
newpic.save("gen.jpg", "JPEG")

This is the picture we get.

Tips for Bash

2009-04-08T07:05:00.000-07:00

Bash is a kind of script language. It's not too formatted. But it's the language used by Linux system. So it's the most direct operation command for Linux. Other script languages, for example, python, perl, have to use bash sometimes. In my mind, if you want to write several lines script to finish your work, BASH is the best choice. I just write down something, which is used by myself when I am working.

tar.
```
 tar -cvzf filename.tgz filename
```
untar.
```
 tar xvzf filename.tgz
```
check the space of some directorie.
```
du -h --max-depth=1
```

process control.


#!/bin/bash

for each in `ps -ef | grep ” | grep -v PID | awk ‘{ print $3 }’`;
do
for every in `ps -ef | grep $each | grep -v cron | awk ‘{ print $2 }’`;
do kill -9 $every;
done;
done

sed. This command will look at the text in 2.txt and substitute the 'new2' to 'CERN'. The new text will be stored in 2.txt.
```
sed  -i 's/new2/CERN/g' 2.txt
```
If you use
```
sed  -e 's/new2/CERN/g' 2.txt
```
This command will just substitute the string, print the new text in monitor and will not be stored in file.
You also can use
```
line="x1.root y1.root x2.root y2.root" 
echo $line | sed  's/y[1-9].root//g'
x1.root  x2.root
```

find.


find ./work/   -mindepth 2 -maxdepth 2 | xargs chmod 744

awk. I don't recommend people to use this awk to get some system information, like the example. Because it's not a good programming way.


#!/bin/bash

ps -ef  | grep gnome |  grep -v grep   | awk '{print $7}'
ps -ef | grep "slot"  | awk '{print $7}' | sed -e 's/-.*//g'  | grep -v ":"

refresh the desktop
```
killall nautilus
```

PS to image.

2009-04-06T06:31:00.001-07:00

ps to png


gs -sDEVICE=png256 -o muon03.png -r800 -dBATCH -dNOPAUS muon.ps
gs -sDEVICE=png256 -sOutputFile=muon03.png -r800 -dNOPAUSE    muon.ps -c quit

eps to png


gs -sDEVICE=png256 -dEPSCrop -sOutputFile=output.png -r800 -dNOPAUSE input.eps -c quit

pdf to png


gs -sDEVICE=png256 -o muon03.png -r800 -dBATCH -dNOPAUS muon.pdf
gs -sDEVICE=png256 -sOutputFile=muon03.png -r800 -dNOPAUSE    muon.pdf -c quit

One bash script to do that


#!/bin/bash
for i in `ls *.ps`;
do gs -sDEVICE=png256 -sOutputFile=${i//.ps/.png} -r600 -dNOPAUSE  ${i} -c quit;
done

You can convert a eps to pdf like this.


gs -dEPSCrop -sDEVICE=pdfwrite -sOutputFile=out.pdf -dNOPAUSE
-dBATCH -dAutoRotatePages=/None -c .setpdfwrite -f input.eps

----------------------------------------------------------------------------------------------------------
Links
How to use Ghostscript
Details of Ghostscript output devices

CSS centralize problem

2009-04-05T08:20:00.000-07:00

It's very difficult to centralize the web page because IE and Firefox have different explanation of CSS code. I wrote a very simple web page these days. But I found my web page is central in Firefox and can not be centralized in IE. We don't like IE. But somebody likes it. So it's better to make it work at IE too.

At first I used one div container.


div.body{
  width: 32cm;
  float: center ;
  margin: 0 auto ;
  padding: 0px;
  text-align: center;
  border: 0px groove;
  }

This setting is working in Firefox because the "margin : 0 auto". But IE can not know this setting. So I looked through the web to get some information. There is one method which is almost good.


div.body{
position:absolute;
top:50%;
left:50%;
margin-top:-240px;
margin-left:-320px;
width:640px;
height:480px;
background:#ECECEC;
}

Actually this is a good setting if you want to get a fixed width web page. But for my case, this is not very good because I don't want to get a fixed width but a unfixed width. I felt upset about the uncompatibility between IE and Firefox. Then I want to give up. Suddenly I got an idea when I was sitting in a meeting. My idea is this. I use two containers. One of them has 100% width using the first method. Then I use a another container in the first container, which has 88% width. When I reload my web page, it looks great.

Emacs Usage

2009-03-31T02:26:00.000-07:00

Emacs is the bese editor I have ever used. It's very good at speed and language format.

.emacs setting

.emacs is a configure file for emacs. When emacs starts, it will run .emacs first. Usually .emacs is at ~/.emacs. Actually .emacs is something like LISP language.

(setq inhibit-startup-message t) is used to shut down the welcome massage when you open emacs. its boring to see a welcome page every time you use emacs.
t means true.
nil means false.
(setq-default make-backup-files nil) is used to shut down the backup automatically. But I recommend you open this function.
(setq require-final-newline nil) will not require a new line in the end of file.
But sometime, (setq require-final-newline nil) does not work. Because /usr/share/emacs/site-lisp/default.el will run after .emacs. At this time, you should switch off the default.el by using (setq inhibit-default-init t). I spent plenty of time on this stupid new line query. Now I can shut it down. But you have to open one thing[7] in .emacs.
(when window-system
;; enable wheelmouse support by default
(mwheel-install)
;; make switching frames works properly under the default click- to-focus
(setq focus-follows-mouse nil) )

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Find and Replace

Find a string : C-s
Find backward : C-r
Find forward : C-s
How to replace a string. M-x replace-string
How to do query replace. M-x query-replace.
You also can do query replace by. M-%

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Rectangular Operations

Sometimes it's very convenient to use the rectangular selection in emacs. When you are learning how to do it, it's painful. But after you get it, it will save you much more time.

Select a rectangular area and copy(cut) it to another place. Go to the left-top of the rectangular you want to select. Hit C-space. Then this point is mark set. Then go to the right-bottom of your rectangular area, and click C-x r r(C-x r k for cut) and Enter. This rectangular area has been copied to register. Move your cursor to the place where you want to put this area, and click C-x r i and Enter. After click enter, the content in register will be copied to the new place.
Select a rectangular area and insert some strings. Hit C-space and click C-x r t and Enter. Then you will enter the text you want insert this area. After hit enter, you will see the text has been inserted.

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Cursor Movement

Move cursor to the beginning of a line : C-a
Move cursor to the and of a line : C-e
Move cursor to the beginning of this file: C-x [
Move cursor to the end of this file: C-x ]

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Multi-Windows

In emacs, you can split the window in to several windows.

C-x 3 will split the window in two columns.
C-x 2 will split the window horizontally.
C-x 0 will shut down one window.
C-x o will change the cursor between different windows.

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Some very useful links
Ted's Blog for emacs
Emacs Keyboard Shortcuts
JW's Tips and Notes: Emacs Example Tutorial: insert a block of text
emacs-fu: working with rectangular selections

A Python function which can combine a list to a string

2009-03-24T03:12:00.000-07:00

Sometime you can use str.split(".") to split a string to a list. It's very easy to operate on this list. But sometime you want to combine the list to a string again after the list operation. I just write a simple python function.

ListName : the name of list which you want to combine
StrInsert : the string which you want to insert to this list


def combineStr( ListName , StrInsert  ):
out_str = ListName[0]
for item  in  range(1, len(ListName)):
   out_str +=StrInsert+ListName[item]                                                       
return out_str

How to take a screenshot in your computer

2009-03-23T10:00:00.001-07:00

Using GIMP

To take a screenshot with the GIMP, find the following menu option: File —> Acquire —> Screen Shot. You will then be offered some options for the screenshot such as length of delay and whether you want to take a screenshot of the entire screen, or just a window.

PrintScreen Button

This method is easy. Put the button in you keyboard. Normally, the PrintScrn is at the right side of F12. After you put this button, there will be one window to ask you how to store this picture.

Use Ubuntu(GNOME)

You can open Applications->Accessories->Take Screenshot.
You will see a window which can help you to take a screenshot.

How to add a public calendar to Google Calendar

2009-03-23T09:44:00.001-07:00

If you need to print out the meeting schedule, you can just add the public calendar of the meeting to Google Calendar. Google Calender will update the time schedule automatically and I don't need to worry about whether the schedule is the latest.

First you should get the link of the public calender. For example, http://indico.cern.ch/categoryDisplay.py/ical?categId=3l94
Then you can go to your google calender.Click the Add->Add by URL. Then you can type the link of you calendar. Enjoy your own calendar.

I have tested the update rate of Google calender. Normally, it will be updated every 24 hours.

If you are familiar with Python script, you can also use the gcalcli.
gcalcli can connect with google calendar by python. First you can get the public calendar by 'wget'. Then you can edit the calendar file and add these files in to google calendar by gcalcli. It's powerful and useful. But in my case, the first method is enough. So I did't dig out the second method.

Delete the contents of your search toolbar

2009-03-23T09:36:00.000-07:00

Sometime if you are using a public computer, you maybe want to delete the search record of your google toolbar.

If you are using firefox,you can openEdit->Preferences->Privacy->Clear Now.

You also can delete the contents directly. You just click the contents of search bar and shift+delete.

I like the second way. It's more easier and quick.