CodeMarvels – Page 20 – All's the Code !

Notes/Technology

Fix Vim editor on Ubuntu

Posted on June 11, 2012 by Kj / 0 Comment

Problem: The arrow keys insert characters, no status message at the bottom etc.

Reason : The default Vim on Ubuntu is vim-tiny, a skeleton version.

Fix: Install the real stuff – sudo apt-get install vim

Note: vi = Visual, vim = Visual improved. And vim-tiny is vi compatible, kind of Jurassic.

Technology

Install Sun (Oracle) Java on Ubuntu without using PPAs

Posted on May 26, 2012 by Kj / 0 Comment

Install JDK on Ubuntu manually without depending on PPAs –

Select the required package from here – http://www.oracle.com/technetwork/java/javase/downloads/index.html. Download the jdk-[version].bin file from the downloads page.
Make the downloaded file runnable; Eg – sudo chmod +x jdk-6u32-linux-x64.bin
Run this file; Eg- sudo ./jdk-6u32-linux-x64.bin
Move the newly created folder to /usr/lib/jvm/. Eg – sudo mv jdk1.6.0_32 /usr/lib/jvm/ (Optionally change the user of this folder to yourselves)

Add the newly added jdk to known java command option –


sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.6.0_32/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.6.0_32/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.6.0_32/bin/javaws" 1

Choose the new java, javac and javaws by running commands-

sudo update-alternatives --config java
sudo update-alternatives --config javac
sudo update-alternatives --config javaws

Run java -version to verify installation. Cheers!

Notes/Technology

Eclipse Compilation error: [function/type] is not accessible due to restriction on required library … rt.jar

Posted on May 26, 2012 by Kj / 0 Comment

Problem : Eclipse gives the error – “[function/type] is not accessible due to restriction on required library … rt.jar” when building a project.

Reason: Project classpath (in the build path) is refers to JRE in place of the JDK in which the Project is configured to work with.

Fix: Go to Java Build Path > Libraries, choose JRE System Library, click Edit button. From the dialog choose Alternate JRE and choose the required JDK.

Notes/Technology

Ubuntu Error: Unable to lock the administration directory (/var/lib/dpkg/)

Posted on May 25, 2012 by Kj / 0 Comment

Problem: Ubuntu gives error “Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?” when using apt-get.

Reason: Another apt-get update working or Update manager checking for updates.

Fix: Close Update manager/ wait of current apt-get update to finish, and try again.

Notes/Technology

Create Shortcut / launcher on Desktop in Ubuntu 12.04

Posted on May 21, 2012 by Kj / 2 Comments

To create a shortcut to an application or location on the desktop (Ubuntu 12+), on terminal run –

Method 1: Installing Gnome Panel

if a shortcut is being created for the first time,
```
sudo apt-get install gnome-panel
```
, else directly do step 2.

gnome-desktop-item-edit ~/Desktop/ --create-new

In the launcher-creation window choose the type and location of the target. Click OK.

Method 2: For application shortcuts only

If shortcut to an installed application is to be created –

Go to Home Folder –> File System –> usr –> share –> applications.
Right click your favourite icon, choose Copy To –> Desktop

(from mhdizam’s comment, verified working)

Notes/Technology

Add a folder to left side pane of Nautilus file manager in Ubuntu

Posted on May 21, 2012 by Kj / 0 Comment

To add a folder to favorites in left tab of nautilus –

Go the required folder.
On title bar (at the top of desktop), go to and click Bookmarks => Add Bookmark.

Miscellaneous

How to record from sound card on Ubuntu ?

Posted on May 14, 2012 by Kj / 2 Comments

Given below is how we can record any streamed audio from sound card :

Install PulseAudio Volume Control from Ubuntu Software center.
Open PulseAudio volume control from Dash home.
Go to “Input Devices” Tab.
In the dropdown “Show” (towards bottom of the pane), select “All Input Devices“.
Set Monitor of Built-in Audio Analog Stereo as default fall back option (by clicking the green icon above it).
Close the volume control.
Open Sound Recorder from Dash. This should now record (only the) sounds played in the computer. You may choose “CD quality MP3” from the “Record as” drop down if you want to store the output as mp3s.

Note – Sound recorder is buggy and doesn’t show output formats in Ubuntu 13x. Audicity is a good alternative to use in such cases.

Notes/Technology

Ubuntu – Unable to resolve host error after a VPN session

Posted on May 12, 2012 by Kj / 0 Comment

Problem: Ubuntu unable to resolve hosts after a disrupted VPN session.

Reason: The DNS server not reset to normal from that of the VPN network.

Fix: On terminal, do –

sudo vi /etc/resolv.conf
Remove the “dns domain” and “dns server” lines from this file.
Save and close the file.
Restart browser or the app which needs to connect to internet.

Notes/Technology

Override certificate error in Cisco AnyConnect Client on Ubuntu 12.04 64 bit

Posted on May 9, 2012 by Kj / 6 Comments

Problem: Cisco Anyconnect client does not give an option to override the “invalid certificate error” and go ahead using the current certificate of the server.

Reason: The current libraries used by Anyconnect client does not support this feature.

Fix: Add libraries from Firefox, as below:

If firefox is not installed, install firefox from Ubuntu Software Center.
On terminal run: sudo cp /usr/lib/firefox/lib*.so /opt/cisco/vpn/lib/
Restart Anyconnect client and connect to required host. The certificate acceptance prompt should appear now.

C++ projects

A Malayalam language text editor for MS DOS/Windows console

Posted on May 8, 2012 by Kj / 0 Comment

A console driven malayalam language editor. Serves as a reference to basics of bit mapping. Suits as a high school project or mid term project for undergraduate courses.

Download : Code | Windows Binaries

Note: Given on as is basis (written by author during high school – 1999 to 2001). Uses plain array as the character buffer – using a linked list would make it faster and can help reduce the flicker. Last successful compilation done almost a decade before.

If you want to create your own font for other languages, heres how –

Make a cross reference of characters and the ascii of the keyboard button to relate that to.
Get a “square line” book. ( one we used for doing maths at lower primary school)
Reserve each page for each character.
On a page outline a rectangle having 16 squares horizontally and 10 squares vertically.
Draw each character inside the above rectangle.
Mark “1”s in all squares where the character’s edges pass through. ( the blank boxes can be imagined as zeroes). Now each character can be seen as 10 lines each having 16 ones or zeroes. This is the bitmap of the character, to be entered in the font-maker later.
Do the above in a new page for each of the characters in the serial order defined in the cross reference.
Compile and run fntmaker.cpp. Give any name for font file when prompted. Add each character as 10 lines of 1s and 0s (using the interactive menu).
Compile and run refmkr.cpp. Give any name for the reference file when prompted. Enter each of the character to ascii mapping created in step 1.
Rename the font file to font1 and ascii-to-character reference file to ref.