Showing posts with label tricks and tips. Show all posts
Showing posts with label tricks and tips. Show all posts

Sunday, 8 February 2015

Uppercase and Lowercase Conversion - Bash Style

After a long long time, I am back with this short post to convert case of strings in bash. While you might have been using tr (Like I did for a while) for this purpose, bash 4 has a built-in way for the case conversion. Withour further ado, here is a session
$ x="samar"

$ echo "${x^}"

$ echo "${x^^}"

$ y="${x^^}"

$ echo $y

$ echo "${y,}"

$ echo "${y,,}"

I hope this helps ;)


Monday, 18 November 2013

Install HTTrack On CentOS

Since I could not find the rpm in the repo, here is the quick How To to install HTTrack website copier on CentOS.

$ yum install zlib-devel
$ wget -O httrack.tar.gz
$ tar xvfz httrack.tar.gz
$ cd httrack-3.47.27
$ ./configure
$ make && sudo make install

This should do all. If you wish not to install zlib compression support, you can skip the first step and run the configure as ./configure --without-zlib. I hope this helps :)


Sunday, 10 November 2013

JPEG To PDF With Imagemagick

ImageMagick is an awesome toolkit with several powerful features for image creation and manipulation. You can use ImageMagick to translate, flip, mirror, rotate, scale, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and Bezier curves. Here, I will show how you can use ImageMagick suite to convert JPEG to PDF quickly.

First make sure imagemagick suite is installed in your system.

$ sudo apt-get install imagemagick

$ sudo yum install imagemagick

Below are some of the examples of using convert which is a part of ImageMagick to convert Jpeg to PDF.

Single Image
$ convert image.jpg image.pdf

Multiple Images
$ convert 1.jpg 2.jpg 3.jpg output.pdf

Resize and Convert
$ convert -resize 80% image.jpg image.pdf

Negate and Convert
$ convert -negate image.jpg image.pdf

You can actually use different available switches to get your output as expected. I usually use PdfTk in conjunction with this technique to work in different scenarios and it really works great. I hope this helps :)


Friday, 18 October 2013

Pattern Based Database GRANT In MySQL

At our workplace, we need to manage database access for different teams and rather than adding another grant on the addition of new database, I've been following a pattern based database access grants in MySQL.

We let different teams work on replicas of same database and hence append the terms such as _dev and _qa as the database prefix. And, we define GRANTS based on these patterns. An example would be something like below:
GRANT ALL ON `%\_dev`.* TO 'user'@'%' IDENTIFIED BY 'password' WITH GRANT OPTION;

I hope this proves useful for some of you guys :)


Thursday, 17 October 2013

How I am Trying To Keep My Eyes Safe On Computer

Lately I've been on computer a lot and with this, the usual problem with most computer users has started to bother me. Going through some of the blogs online for keeping eyes safe while using computer, I came through few suggestions and in this post, I'm writing how I'm trying to keep my eyes safe. Though not tremendously helpful for everybody, I thought I would share this and you could also use my technique.

The problem with computer addicts is not getting their eyes off the computer for much longer period and though I've been trying to remember to keep my eyes off the computer in regular interval, I usually never implement this.

My two principles based on my readings on different websites are:

  • 20-20-20: In the 20 minutes interval, keep your eyes away for 20 seconds (& view other objects which are around 20 feet away)
  • 2 hrs rule: In the 2 hours interval, stay away from computers for at least 2 minutes.

But, you can not really follow the rules so easily and I had to find some other alternative to do so. This is how I am doing it now.

Create two cron jobs for each of the above mentioned methods such that notify-send is triggered in each 20 minutes and each 2 hours informing you to keep yourself safe from computers. So my /etc/crontab looked like this:

*/20 * * * * techgaun export DISPLAY=:0.0 && /usr/bin/notify-send -i /home/techgaun/Samar/scripts/eye_inv.ico "20 - 20 - 20" "Time to take rest. Keep your eye safe :)"
01 */2 * * * techgaun export DISPLAY=:0.0 && /usr/bin/notify-send -i /home/techgaun/Samar/scripts/eye_inv.ico "2 hrs eye rest" "Time to take rest for 2 minutes. Keep your eye safe :)"

You need to replace techgaun with your username and need to give correct path to the ico file if you like to use icon like me. Otherwise, you could just omit the icon in notify-send command. I hope this proves useful for some of you :)


Monday, 16 September 2013

Two Ways To Print Lines From File Reversely

Ever tried to print lines in files in the reverse order? You will know two simple methods to print lines from file in the reverse order.

Imagine a file somefile.txt with content something like this:

Method 1:

$ tac somefile.txt

Method 2:

$ sort -r somefile.txt

You can achieve the same effect through other techniques as well but I'll stick to these simple ones :)


Friday, 28 June 2013

Rename MySQL root User [How To]

MySQL ships with the default user 'root' who has all kind of access to the MySQL database. We often wish to rename this user to something else because of maybe security issues or any other reason. While renaming 'root' to something else is not going to alleviate all sorts of security problems that may arise, it is good idea to rename 'root' to some other name.

Login to the MySQL console and then type the following SQL statements:

mysql> use mysql;
mysql> update user set user="some_other_user" where user="root";
mysql> flush privileges;

It is often good idea to drop anonymous users and the test database because of security reasons. I bet you are never going to use that test database so why keep it? Run the SQL statements as below to do so:

mysql> drop user "";
mysql> drop database test;

Also, make sure you use strong passwords. You can use mysqladmin to change passwords.

$ mysqladmin -u my_new_user -p password 's0m3_r4nd0m_$|r0ng_p455' $ history -c $ rm ~/.mysql_history

The later two commands are to ensure that no log of any of your MySQL queries or admin level commands have been stored in the history.

I hope this helps :)


Wednesday, 19 June 2013

Customizing Jenkins Layout

We use jenkins as our continuous integration server at our workplace and without any doubt, its the best CI tool I've used. We had been thinking of customizing jenkins layout to fit our company and thanks to the plugins developed by people who make jenkins not just another random tool on the internet, but the software WITH awesome community. There are particularly two plugins that seemed to fit our scenario. The first one is Simple Theme Plugin and the second one is Page Markup Plugin.

The later one does allow to add markups to the page but didn't best fit for our scenario. So we decided to use the Simple Theme Plugin. Installing the plugin is straightforward in jenkins. Once the Simple Theme Plugin is installed, a new content box will appear in your Manage Jenkins -> Configure System which will look something like below:

This plugin requires you to specify your own custom .css and .js file. The good thing about jenkins is you can place your own content at the JENKINS_INSTALL_DIR/userContent/ directory and then access it via http://yourbuildserver.tld/jenkins_path/userConent/yourfile.ext. I was working on the windows system where my jenkins install was at C:\.jenkins\ and hence I placed my CSS and image files inside the userContent directory of jenkins install folder. This should not be very difficult on any other systems if you are familiar with jenkins and your OS.

You can grab the jenkins css files from the webapp root directory (I was using tomcat so I grabbed it from inside there) and then edit the css as per your necessity. In my case, I had to change the header style only so my CSS looked something like below:

#top-panel {
  background-size:100% 100%;
  height: 43px;
#top-panel td#login-field span a {
    background: none; }
#top-panel a {
    background: url("title.png") 0 0 no-repeat;
    display: block;
    width: 107px;
    height: 27px;
    margin: 10px 0 -5px 0px; }
#top-panel td > a img {
      display: none; }

This is all you have to do. Btw, don't fall for the readme.txt inside userContent directory which says: "Files in this directory will be served under your http://server/jenkins/userContent/". Make sure you specify the URL according to your server configuration not according to this specification thus appending "/jenkins" in your URL.