Shared Knowlege, Keep It Handy

Suppress some Spotlight activities on Mac

2014-06-02T14:26:00.003-07:00

I use git for work and most of the time, with a lot of branches. Every time I switch from branch to branch, and do a clean build, Spotlight gets so busy in the background (mds, mdworker). All those indexing work takes a lot CPU time and disk IO. But those efforts are pretty wasted. I use IDE for text search, and in another hour or two, I switch to another branch.

It is possible to suppress some Spotlight activities. From System Preferences, Spotlight, in the privacy tab, put the directory of git repository in the not-to-index list. Save CPU usage, battery, and generate less heat.

Disable trackpoint on ThinkPad running Ubuntu

2013-02-02T13:16:00.003-08:00

I run Ubuntu 12.04.1 LTS on ThinkPad. Most of the time, the track point gets in the way. I disable it with this command,

xinput -set-prop "TPPS/2 IBM TrackPoint" "Device Enabled" 0

GIMP 2.8 has arrived

2012-07-10T11:01:00.002-07:00

GIMP (GNU IMAGE) 2.8 is here.

It just occurred to me the other day that GIMP was working on 2.8. I thought I would like to check it out. When I got there (www.gimp.org), it is there.

I like the single view mode (under menu Windows, Single-Window-Mode). It solved the only complaint I had with GIMP in the past. That is to click twice in order to re-focus on the other window when switching between tool/editor/layer windows.

I have not checked out what else is new in it. GIMP is one of a few open source projects I appreciated and used frequently. I would expect to continue creating a lot of digital assets from GIMP for my iPhone app projects.

Combine gmail and Java mail library to create your email compaign

2012-03-30T11:34:00.000-07:00

If you use gmail for your company, you can run your own email campaign without paying those email campaign companies. Write a small script or Java program to pull user data from your database and create a pretty HTML based email template. If you want to track them, insert the tracking in the HTML content. Use the following code to start sending emails to your users. Just be sure not to abuse the gmail account.

import java.io.File;
import java.util.Date;
import java.util.List;
import java.util.Properties;
import javax.activation.DataHandler;
import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.*;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeBodyPart;
import javax.mail.internet.MimeMessage;
import javax.mail.internet.MimeMultipart;

public class Mailman extends javax.mail.Authenticator
{
private String smtpServer;
private String from;
private String password;
private boolean useAuth;

public Mailman(String sender)
{
from = sender;
smtpServer = "smtp.gmail.com";
}

public String getSmtpServer() { return smtpServer; }
public void setSmtpServer(String svr) { smtpServer = svr; }

public String getSender() { return from; }
public void setSender(String fm) { from = fm; }

public String getPassword() { return password; }
public void setPassword(String passwd) {
password = passwd;
if (passwd != null && passwd.length() > 0) {
useAuth = true;
} else {
useAuth = false;
}
}

/*
* This method sends plain text mail.
*/
public void send(String subject, String body, String to, String cc)
{
try
{
Message msg = createMessage(subject, to, cc);
msg.setText(body);
Transport.send(msg);
}
catch (Exception ex) {
throw new RuntimeException(ex);
}
}

/*
* this method sends mail with file attachments
*/
public void send(String subject, String body, List<String> attachPaths, String to, String cc)
{
try
{
Message msg = createMessage(subject, to, cc);
Multipart multipart = new MimeMultipart();
MimeBodyPart messageBodyPart = new MimeBodyPart();
messageBodyPart.setText(body);
multipart.addBodyPart(messageBodyPart);

for (String fileAttachment : attachPaths) {
MimeBodyPart attachment = new MimeBodyPart();
DataSource source = new FileDataSource(fileAttachment);
attachment.setDataHandler(new DataHandler(source));
attachment.setFileName(new File(fileAttachment).getName());
multipart.addBodyPart(attachment);
}
msg.setContent(multipart);

Transport.send(msg);
}
catch (Exception ex) {
throw new RuntimeException(ex);
}
}

protected Message createMessage(String subject, String to, String cc) throws Exception
{
Properties props = System.getProperties();
props.put("mail.smtp.host", smtpServer);
Session session = null;
if ( useAuth ) {
props.put("mail.smtp.starttls.enable","true");
props.put("mail.smtp.auth", "true");
// SSL
props.put("mail.smtp.socketFactory.port", "465");
props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
props.put("mail.smtp.socketFactory.fallback", "false");

session = Session.getInstance(props, this);
} else {
session = Session.getInstance(props);
}
// create a new message
Message msg = new MimeMessage(session);

if (from == null) {
from = System.getProperty("user.name");
}
msg.setFrom(new InternetAddress(from));
msg.setRecipients(Message.RecipientType.TO, InternetAddress.parse(to, false));
if (cc != null) {
msg.setRecipients(Message.RecipientType.CC, InternetAddress.parse(cc, false));
}

// set the subjecttext
msg.setSubject(subject);
// set some other header information
msg.setHeader("X-Mailer", "s3ar-JavaMail");
msg.setSentDate(new Date());

return msg;
}

@Override
public PasswordAuthentication getPasswordAuthentication()
{
// you can read the password from a file
// which should set mode as 0400

return new PasswordAuthentication(from, password);
}
}

Update xcodebuild path

2012-03-26T11:22:00.002-07:00

The installation directory of Apple's IDE, Xcode, moved from /Developer to /Applications starting version 4.3.1. It caused some glitches for tools, such as xcodebuild, if invoked as a command-line utility.

To point it to the new installation base, use
sudo /usr/bin/xcode-select -switch /Applications/Xcode.app/

Verify the change with
/usr/bin/xcode-select -print-path

Examine multiple files in command less

2012-03-19T10:29:00.000-07:00

To change to the next file after opening multiple files simultaneously in 'less' command, use this command

:n

And to change to the previous file, use

:p

The instruction should also be available from the man page.

Create symbolic links in Windows 7

2012-03-11T17:18:00.000-07:00

I was running XAMPP on Windows 7 and tried to use symbolic link point to the folders with PHP code. The soft link created in Cygwin (ln -s <directory> <link-name>) did not seem to be recognized by Apache. I found I need to use native Windows command in the command prompt.

Run Command Prompt as administrator
> MKLINK /D <link-name> <target directory>

Note

I tried to use secpol.msc to grant myself with privilege for creating symbolic link.
secpol.msc via Start or Start → Run.
Open Security Settings → Local Policies → User Rights Assignment
It did not give me the permission to create symbolic link even after I re-log in. I have to run the command as administrator.

The chown command equivalent in Windows 7

2012-03-11T16:57:00.003-07:00

As 'su - chown' does not work in Cygwin, there is a alternative in Windows 7.
Log in as the user the files should be changed TO and run Command Prompt as administrator.
Run the follow command (or similar one with different parameter combination)

> takeown /F <directory name> /R

Black screen on simulator for iPad retina using cocos2d

2012-03-09T17:41:00.001-08:00

I am excited to see that iPad has a retina display. As I am developing my first iPhone/iPad game (universal application) using cocos2d 1.0.1, I updated my Xcode to 4.3.1 to see if my code still works on the new device display.

It showed a black screen. Nothing displayed. But the code seems to be running and responding to touch events. I did not know what happened so I started to search on the web. I found one posting on cocos2d-iphone forum started a day ago was discussing exactly the same problem. I read every post and experimented all the proposed solutions. I don't think it is anything to do with '-hd' image files, as the sample cocos2d HelloWorld did not work in iPad retina display either. But apparently lowering the resolution makes everything work again. I noticed one member mentioned something particularly interesting, which was about the call to

gluPerspective() in CCDirectorIOS -setProjection().

The call stack is

enableRetinaDisplay => setContentScaleFactor => setProjection, as enableRetinaDisplay is the center of the discussion.

I found that switching to the commented code one line before the now in-use code in CCDirectorIOS makes my code work again in all the simulators. I posted it to the thread. But here is the complete posting. Hope this helps you as well.

I was following DonomaGames's post on gluPerspective() (CCDirectorIOS line 212-213). Line 212 was commented out and replaced with line 213,

gluPerspective(60, (GLfloat)size.width/size.height, 0.5f, 1500);

which has zFar as 1500. I did a calculation using the formula on 212, zNear=zeye-height/2, zFar=zeye+height/2. On iPad retina, the zFar value is 2794.707275. It is larger than 1500. The rendering may be clipped off.

For comparison I computed the whole four types.

Type	zNear	zFar
iPhone SD	175	655
iPhone HD	350	1310
iPad SD	373	1397
iPad HD	746	2794

Given that, I changed line 212 in CCDirectorIOS.m to

gluPerspective(60, (GLfloat)size.width/size.height, 0.5f, 2800);

It worked for iPad retina simulator.

I also tried the following code and worked also.

if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad &&

[[UIScreen mainScreen] scale] > 1.0 )

{

gluPerspective(60, (GLfloat)size.width/size.height, zeye-size.height/2, zeye+size.height/2 );

} else {

gluPerspective(60, (GLfloat)size.width/size.height, 0.5f, 1500);

}

This combines the original 212 and 213 code.

Hostname on Mac OS X

2012-03-05T10:42:00.002-08:00

If the dynamic hostname is provided by DHCP, and you prefer a fixed one, there are a few ways to do it.

From System Preferences/Network

Select the network adapter which interfaces the DHCP server.
Click on the "Advanced" button on the lower right.
In the TCP/IP tab, specify the "DHCP client ID" text field.

Or depending on the version of Mac OS:

-- Mac OS X 10.5 and older
On Mac, the hostname shown on the terminal prompt is configured by the file,
/etc/hostconfig. If it is specified as
HOSTNAME=-AUTOMATIC-,
the name shown in the prompt is provided by DHCP or BootP server.

Change that line to
HOSTNAME=(preferred-name)

-- Mac OS X 10.6 and newer
Use the command scutil (system configuration utility)
scutil --set HostName (preferred-name)

Remember to check the name set in
/Library/Preferences/SystemConfiguration/preferences.plist,
under System/System/ComputerName

Modify grapeConfig.xml to speed up groovy script with @Grab

2012-02-23T14:57:00.000-08:00

I had a post on speed up groovy script startup time if Grape @Grab annotation is used in the script.
The cause is described in this post, http://swainya.blogspot.com/2011/09/skip-download-when-groovy-code.html.

The solution described in that post is to add one line in the .groovy/grapeConfig.xml to decrease cache TTL. Add

<property name="ivy.cache.ttl.default" value="15m"/>

in the <ivysettings> section.

Your grapeConfig.xml will look like this after adding that line

<ivysettings>
<property name="ivy.cache.ttl.default" value="15m"/>
<settings defaultResolver="downloadGrapes"/>
......

Show user Library folder in Finder

2012-01-13T11:30:00.000-08:00

Since moved to MacOS Lion (10.7.x), the folder Library disappeared from my Finder window. It bothers me a lot. Apparently Apple hides it in this OS release. Here is the way to reveal it.

From console terminal, use this command.

$ chflags nohidden ~/Library/

Comment out multiple lines in vi

2011-12-30T11:24:00.000-08:00

Press Ctrl-v to start a VISUAL BLOCK
Move the cursor (up/down arrow key) to expand the block
Press I (Shift-i) to start insert.
Type in the character(s) that you want to insert, such as #, or //.
Press ESC to leave the visual block.

Global search in vi and list results

2011-12-06T12:08:00.001-08:00

We use the simple command to search a pattern (or a fragment of text),

:/{pattern}

Sometimes, there would be a few dozens of matches that you want to list and browse quickly. Use this command,

:g/{pattern}

It lists the search results in one buffer. If you want to search the pattern case insensitive, add \c in the command, like

:g/\c{pattern}

Monitor disk IO activities on a Linux host

2011-11-01T17:39:00.000-07:00

1. Use df first to find all the devices
2. Use iostat

iostat -dx <device> <time-interval>

For example,
iostat -dx /dev/sdb 5

to display disk IO activities every 5 seconds.

Find CPU information on a Linux

2011-10-27T13:30:00.000-07:00

A good tip for finding out CPU and 32/64 bit kernel information on a Linux host, at http://www.cyberciti.biz/faq/linux-how-to-find-if-processor-is-64-bit-or-not/

In short, use

uname -a

and

cat /proc/cpuinfo

Find directory path of the current groovy script

2011-09-30T10:58:00.000-07:00

Bash or PHP script has a function that returns the directory path of the current script file.

$my_dir=dirname(__FILE__);

Groovy script lacks such a capability but an alternative is available by calling

def my_dir = new File(getClass().protectionDomain.codeSource.location.path).parent

Skip download when groovy code annotated with Grapes

2011-09-27T11:37:00.000-07:00

Grapes is a great utility to manage class path automation when coding with groovy.
http://groovy.codehaus.org/Grape
But it slows down the start-up if there are a lot of dependent jars to download. Even all the dependent jar files have been downloaded to local m2 and grapes store previously, the download process still takes place, which slow things down unnecessarily.

Use the following options to ask groovy look into local storage directly.
groovy -Dgroovy.grape.autoDownload=false [groovy file path] [arguments ......]

Suppress test stage during maven build

2011-09-23T18:00:00.000-07:00

Use
-Dmaven.test.skip.exec=true
to skip running test cases without skipping test jar build

A class path with all jar files in a folder

2011-09-23T11:46:00.000-07:00

Typing in all the jar files to form a class path is not a fun job. This quick trick may alleviate some of the pain.

export CLASSPATH=`echo $PWD/*.jar | sed 's/ /:/g'`

Customize the "echo" part to get all the files needed.

Such as

export CLASSPATH=`echo $PWD/*.jar . $HOME/lib | sed 's/ /:/g'`

Use wildcard in the command find

2011-08-18T12:03:00.000-07:00

To use a wildcard * in the find command needs a little more care.

Without quote or backslash \, such as
find . foo*bar -print
the shell will expand * before passing it into find command. This results is a different, and most likely a narrower, search.

To avoid that, use
find . 'foo*bar' -print
or
find . foo\*bar -print

Add one more yum repository

2011-08-16T16:15:00.000-07:00

Read yum.conf first. Usually the path is /etc/yum.conf.
Understand where the cache and repository configuration file directory

The following examples use default locations

## add epel to the repo list
## see what is there before change
ls /var/cache/yum/*/*
cd yum.repos.d/
## copy contents from another configured host
sudo vi epel.repo
sudo yum clean all
## make sure it is empty
ls /var/cache/yum/*/*
sudo yum makecache
## see if the new repo epel is added
ls /var/cache/yum/*/*
## add GPG key for the new repo, also do copy-paste
sudo vi /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL

If you are not sure about the name of RPM-GPG key, run rpm to install the package. Towards the end, rpm will complain about missing the GPG key and prompt the file name for you.

Find out it is a 32 or 64-bit Linux

2011-08-16T15:20:00.001-07:00

Use the command
uname -m
If it shows x86_64, it is a 64-bit host.
If it shows i386 (or sometimes i686), it is a 32-bit machine

Plus, run the command
file /bin/ls
For 64-bit kernel, it should show
/bin/ls: ELF 64-bit LSB executable ....

Find installed packages on Linux hosts

2011-08-16T14:30:00.000-07:00

To find installed packages on a Redhat/CentOS Linux, use

rpm -qa | less

Once the package name is found, use this command to find more details

rpm -qil {package-name}

To find installed packages on a Debian (also Ubuntu) Linux, use

dpkg --list 

Once the package name is found, use this command to find more details

dpkg -p {package-name}

Find and delete into directories recursively

2011-08-09T13:28:00.000-07:00

How to find a set of files or directories that are named the same? For example, to delete all the '.svn' directories in the current working directory.

One easy way is

rm -rvf `find . -type d -name .svn`

The option [-v] prints out the files/directories found. and rm -rf is the typical force deletion of a directory.

Another way to do it is

find . -name ".svn" -exec rm -rf {} \;

But this command prints out warning messages that sometimes confuse users.

find: ./.svn: No such file or directory

find: ./images/.svn: No such file or directory

The warning message means it found a .svn directory in the current directory and deleted as instructed ( -exec rm -rf ). When the command find wanted to descend into .svn directory, it could not.

The trailing {} \; is required. Pay attention to its format: there is a space between } and \.