Step By Step Turbo C++ IDE In Ubuntu 12.04

Well we are doing our labs based on the traditional Turbo C++ IDE and I decided to write this blog post with the information on how I installed it on my Ubuntu box.

First thing first, download Turbo C from internet. For your ease, I've uploaded it HERE.

We will have to install dosbox to run the windows dos mode applications so lets install it:

samar@samar-Techgaun:~$ sudo apt-get install dosbox

Once you install dosbox, unzip the content to somewhere in your $HOME directory. In my example, I unzipped the content of the Turbo C zip file into ~/Tools/TurboC3/. Now launch the dosbox by typing dosbox in the terminal. A dosbox emulation window will appear which will look like your old DOS system.

In the window, type the following (make sure you type appropriate path for your installation):

mount C: ~/Tools/
C:
cd TurboC3
INSTALL.EXE

And, then follow the on-screen information. Refer to the screenshots below:















Once the installation finishes, you can then run the Turbo C by mounting the drive again and then navigation to C:\TC (cd C:\TC\BIN). If you need to use the Turbo C++ IDE frequently, my suggestion would be to add an autoexec entry in your dosbox configuration. The default configuration file resides in ~/.dosbox/dosbox-0.74.conf (My version of dosbox is 0.74 hence the file name, by default). Open up this file and in the section of [autoexec], add the lines below:

[autoexec]
mount C: ~/Tools/
C:
cd TC\BIN
TC.EXE

Adding this entry will run the above commands during the startup of dosbox thus giving you the Turbo C IDE interface directly on running dosbox.

I hope this helps :)


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Check Battery Status From Terminal [How To]

Since I had no graphical interface for some reason, I needed some alternative way to check the battery status. If your system includes acpi command, you can just use this command but I had no luxury of such command and here's how you can do the same thing I did. The /proc/ virtual file system has information of different states among which the ACPI information is one. The ACPI information provides us the details of device configurations and power status of the system. Below is one flavor of the command to check the battery status:

samar@Techgaun:~$ cat /proc/acpi/battery/BAT0/state
present: yes
capacity state: ok
charging state: charged
present rate: unknown
remaining capacity: unknown
present voltage: 12276 mV

samar@Techgaun:~$ cat /proc/acpi/battery/BAT0/info
present: yes
design capacity: 4400 mAh
last full capacity: unknown
battery technology: rechargeable
design voltage: 10800 mV
design capacity warning: 250 mAh
design capacity low: 150 mAh
cycle count: 0
capacity granularity 1: 10 mAh
capacity granularity 2: 25 mAh
model number: Primary
serial number:
battery type: LION
OEM info: Hewlett-Packard

The first command provides the general status of the battery and the second command provides the detailed information about battery. The other way is to use the upower command that talks with the upowerd daemon. Upowerd daemon is a default daemon in ubuntu and few others for power statistics. Below is the command to see battery details:

samar@Techgaun:~$ upower -i /org/freedesktop/UPower/devices/battery_BAT0
native-path: /sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0
vendor: Hewlett-Packard
model: Primary
power supply: yes
updated: Sat Mar 9 10:12:17 2013 (5 seconds ago)
has history: yes
has statistics: yes
battery
present: yes
rechargeable: yes
state: empty
energy: 0 Wh
energy-empty: 0 Wh
energy-full: 47.52 Wh
energy-full-design: 47.52 Wh
energy-rate: 0 W
voltage: 12.28 V
percentage: 0%
capacity: 100%
technology: lithium-ion

If you wish to install acpi for future uses, you can do so by typing the command below:

samar@Techgaun:~$ sudo apt-get install acpi

Play around with different switches by looking over the help and man pages. You will find this tool quite useful :)


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Chaining The Proxies With ProxyChains

In this tutorial, we will learn to redirect our TCP traffics through the chain of proxies using a well known tool named ProxyChains.

ProxyChains is a tool for tunneling TCP and DNS traffics through chain of several proxy servers which supports HTTP, SOCKS4, and SOCKS5 proxy servers. Hence, this tool leverages several usages such as anonymity, bypassing filters, running any program through proxy servers, etc.

You can DOWNLOAD proxychains from SourceForge. In ubuntu, you can directly install it from repos:

samar@samar-Techgaun:~$ sudo apt-get install proxychains

Once you have installed the proxychains, you need to configure this tool. The global configuration file is located at /etc/proxychains.conf so if you wish to have your own configuration file, you could either create the proxychains.conf file in the current working directory or at $HOME/.proxychains/proxychains.conf.

In my example, I'll edit the global configuration file by issuing the command:

samar@samar-Techgaun:~$ sudo nano /etc/proxychains.conf

First, we will have to select the kind of chaining option we want to use. We can use one of the dynamic_chain, strict_chain, and random_chain chaining options. In most cases, it is good to just use the dynamic_chain so we uncomment the line containing dynamic_chain and comment all other chaining options.



Then we need to grab some proxies and then insert at the end of our configuration file which would look like:

socks4 127.0.0.1 9050
socks5 192.168.2.90 3128
socks5 1**.1**.*.* 8080

You could add as much as proxy servers in the list. Btw, the asterisks in the above example do not mean wildcards, they are just there to symbolize some proxy server. There are free sites on the Internet which provide big database of different kinds of proxies. Even several proxy scrapers are available all over the internet and you could even write one on your own. So getting list of good proxies is not the difficult job. Once you finish the configuration, you can run any command through proxychains. The syntax is as simple as below:

samar@samar-Techgaun:~$ proxychains <any_command>

For example, below is the example nmap scan run through the proxychains:

samar@samar-Techgaun:~$ proxychains nmap -p 1-1000 -O victim.tld

P.S. If you are interested in some GUI for using proxychains, you can use ProxyChainsGUI. Lastly, the default package from Ubuntu repository seems to be missing the proxyresolv command so I would recommend to compile the source code locally.
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Search Text Over Multiple PDF Files In Linux

You can use the old grep command or the small script using the pdftotext command to search text over multiple pdf files but we are talking about a simple utility that lets us to search text in PDF files.

The pdfgrep tool lets you perform grep style search over multiple pdf files easily from the terminal. It depends upon the poppler package and under ubuntu, you can just type the command below to install pdfgrep.

samar@\Techgaun:~$ sudo apt-get install pdfgrep

Once pdfgrep is installed, you can perform any kind of search like you would do while using the grep command. Enjoy grepping the PDF files :)


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Swasthani.com Swasthani Ripper

Yesterday I came to know that I can listen Swasthani online at this site, www.swasthani.com and I decided to write a swasthani audio downloader. Since it would be useful for everyone, here is the script.

From the site itself, Sri Swasthani Brata Katha is a very popular ritual observed in Nepal in the Poush month (January – February) during winter. Goddess Sri Swasthani, known to grant wishes of her devotees, is worshipped for the whole month of Poush. The Swasthani Brat Katha (story) is recited everyday. The month long telling of the tales are dedicated to the Goddess and the stories that are mainly narrated are those of Swasthani Devi, Lord Shiva and other Gods.

#!/bin/bash
###############################################
# Swasthani.com Swasthani Ripper       #
# Samar @ http://www.techgaun.com       #
###############################################
if [[ ! -f /tmp/swasthani.txt ]]
then
 wget http://www.swasthani.com/ -O - | egrep '<li class="leaf( first| last)?"><a href="/swasthani/' | grep -o '<a .*href=.*>' | sed -e 's/<a /\n<a /g' | sed -e 's/<a .*href=['"'"'"]//' -e 's/["'"'"'].*$//' -e '/^$/ d' > /tmp/swasthani.txt
fi

while read -r line
do
 wget "http://www.swasthani.com$line" -O - | egrep 'data="soundFile=http://www.swasthani.com/system/files/' | cut -d\" -f6 | cut -d= -f2 | wget -nc -i -
done </tmp/swasthani.txt

Save the above file as swasthani, then chmod for executable permission and run it. If you have problem copying above code, you can check the Swasthani Downloader at GitHub. Enjoy listening Swasthani, geeks :)


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How To Check Which Groups You Belong To

In this post, you will get to know about a simple command that lets you know what groups the particular user belongs to. Users and groups are the one of the several concepts employed in the Linux systems for access control.

From the man page, the groups command does is:
Print group memberships for each USERNAME or, if no USERNAME is specified, for the current process (which may differ if the groups database has changed).

So if you are interested in finding what group a particular user is in, run the command as below. Replace samar with your USERNAME and you are good to go:

samar@Techgaun:~$ groups samar

samar : samar adm cdrom sudo vboxusers ....

I hope this proves useful :)


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Create Backup Of List Of Apps Installed In Ubuntu

When my laptop's HDD was near to death, I had created backup of the list of all applications and packages I'd installed in my Ubuntu so that I would be able to install them easily in my new system in new HDD. I had forgotten about it but today suddenly remembered and am sharing this simple technique. Fire up the terminal and type the following:

samar@Techgaun:~$ sudo dpkg --get-selections > installed_apps

Now the list of packages will be saved in the installed_apps file and you can use it for future reference. I hope this is useful ;)


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Evince Rocks! Foxit Sucks

Been using foxit PDF reader for a while in Windows 7 while I was working on some windows-based project and I was totally pissed off with foxit.

Not being a fan of Adobe's PDF reader, I decided to try foxit PDF reader since some of the online reviews were stating Foxit to be a great PDF reader. Basically, I was looking for a very simple, fast, and lightweight PDF reader that suits me. Foxit has everything a good PDF reader should have. It works pretty well with any PDF documents I need to read. It is supposedly lightweight, fast, secure, and it has millions of users. But, it was neither fast nor lightweight in its default configuration, in my experience.

But its still lacking some feature, that I do not know. I just can not feel the software. I am not satisfied with the level of user experience this software imparts. What do you guys have to say about this??

Then I decided to use the famous PDF reader from linux world, the Evince. And, what can I say?

Evince ROCKS!!!

If you have not tried evince for windows, download it from Gnome's Evince page and try right away on Windows. It should work on Windows XP, Vista, and 7.

Download Evince

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Basic Guide To Crontab

Well it has been a busy week and now I am back with this basic guide to running cron jobs in linux.

Cron is a time-based job scheduling program which comes shipped with most linux distributions and enables users to execute commands or set of scripts automatically at the specified time. Cron is particularly important for system administration and maintenance though it can be used for any general purpose such as scheduling your porn downloads. My post is based on the Vixie Cron, a popular implementation of Cron by Paul Vixie which is by default the cron program in Ubuntu. Other implementations of the cron are anacron, fcron, and dcron.

The cron daemon runs automatically during the startup and consults the crontabs (shorthand for cron tables) for jobs to executed. Crontabs are nothing but files containing the commands to be run at the specified time, however there is a particular (& simple to remember) syntax for cronjobs to be run. You could directly edit these cron tables files but that's not the recommended way. You should always use the crontab editor to add/update jobs to the crontabs.

Cron searches its spool area (located at /var/spool/cron/crontabs) for crontab files which are named after the user accounts from /etc/passwd. As a matter of precaution, you should not directly manipulate the files in there. Additionally, cron reads the /etc/crontab file and all the files in /etc/cron.d. Also, there are other folders: /etc/cron.daily, /etc/cron.hourly, /etc/cron.monthly, and /etc/cron.weekly. And, the name of folders are obvious so if you put the scripts in one of these folders, your script will run either daily or hourly or monthly or weekly.

Since you got several files associated with cron, you have bunch of options on running the cron jobs in your system. First lets start with the crontab tool which is used to install, deinstall or list the tables used to drive the cron daemon. If the /etc/cron.allow file exists, then you must be listed (one user per line) therein in order to be allowed to use this command. If the /etc/cron.allow file does not exist but the /etc/cron.deny file does exist, then you must not be listed in the /etc/cron.deny file in order to use this command.

The crontab command provides following options:

        -e edit user's crontab
 -l list user's crontab
 -r delete user's crontab
 -i prompt before deleting user's crontab

crontab can be configured to use any of the editors.

To list the user's crontab, use the following command:

$ crontab -l

To delete existing cron table, type:

$ crontab -ir

To install new cron table, type:

$ crontab -e

If you are wishing to add commands that require root privilege for execution, make sure you prepend sudo in the above command to add such commands to crontabs. The cron table expects each line of cron job in the following format:

m h dom mon dow command
i.e.
minute hour day_of_month month day_of_week command_to_run

These columns take the values in the range below:

  Minute (0 - 59)
  Hour (0 - 23)
  Day of month (1 - 31)
  Month (1 - 12)
  Day of the week (0 - 6, 0 representing sunday, 6 saturday)

Apart from these values, the cron entries accept other special characters. In each of these five columns:

• An asterisk (*) stands for "every".
• Slashes (/) are used to describe increments of ranges eg. */15 in minutes column would execute the specified command regularly and repeatedly after 15 minute.
• Commas (,) are used to separate items of a list. eg. using 1,2,3 in the 5th field (day of week) would mean Mondays, Tuesday, and Wednesday.
• Hyphens (-) are used to define ranges. For example, 2-5 in the 5th field would indicate Tuesday to Friday.

Now we know the format of how should each line of cron entry should look like, lets see some examples.

Run backup at 5 a.m every Monday

0 5 * * 1 /bin/mybackup

Run backup at 12:01 a.m monday-thursday

1 0 * * 1-4 /bin/mybackup

Run backup at 12:01 a.m on monday and thursday

1 0 * * 1,4 /bin/mybackup

Run backup every minute

* * * * * /bin/mybackup

Run backup every 15 minutes repeatedly

*/15 * * * * /bin/mybackup

The information below is taken directly from man 5 crontab and can serve as a good reference for special strings in place of the 5 columns:

              @reboot        Run once, at startup.
              @yearly        Run once a year, "0 0 1 1 *".
              @annually      (same as @yearly)
              @monthly       Run once a month, "0 0 1 * *".
              @weekly        Run once a week, "0 0 * * 0".
              @daily         Run once a day, "0 0 * * *".
              @midnight      (same as @daily)
              @hourly        Run once an hour, "0 * * * *".

Now that you are feeling better with cronjobs, we will see how we can add cronjobs in the /etc/crontab file. The different thing about this crontab file is that there is an extra column for user field so that the particular cron entry is executed as the specified user.

The format for cron entry is similar to what we've seen already, with an extra column for user.

m h dom mon dow user command

You can use any text editor such as nano or vi to edit the /etc/crontab file.

Finally, once you update crons, make sure to restart the cron daemon to ensure your new cron entries get read by the daemon.

$ sudo service cron restart

I hope this primer for crontab helps you in your job scheduling job :D


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Video Transcoding With HandBrake In Linux

HandBrake is a GPL-licensed, multiplatform, multithreaded video transcoder available for major platforms: linux, mac, and windows. HandBrake converts video from nearly any format to a handful of modern ones.

Handbrake can save output in two containers, MP4 and MKV and I've been using it as a MKV transcoder for a while and I'm quite satisfied with it. Even though the official wiki says its not a ripper, I can see it to be quite useful DVD ripper.



Handbrake is available in CLI (HandBrakeCLI) and GUI (ghb) mode. Hence this offers the flexibility to choose the appropriate version according to your linux personality. As of now, we can install HandBrake from PPA and the latest version is v. 0.9.8 released back in July this year.

HandBrake can be installed from PPA. Issue the following commands in your terminal

$ sudo add-apt-repository ppa:stebbins/handbrake-releases
$ sudo apt-get update
$ sudo apt-get install handbrake-cli

Or if you wish to install the GUI version, type:

$ sudo apt-get install handbrake-gtk

I recommend using the CLI version since you can transcode/convert videos much more efficiently if you use the CLI version. But if you are not comfortable with the command line interfaces, the GUI version of HandBrake is also quite good.

Only problem I have felt is the naming convention of the commands for both the GUI and CLI versions of the tool. In order to run two versions of this tool, you need to type HandBrakeCLI for CLI version and ghb for the GUI version. The problem here is with the naming convention for the binaries. I mean, the names handbrake-cli and handbrake-gtk would be more straightforward than these badly chosen names. Otherwise, the tool does pretty good job of video conversion and can be good alternative if you are not comfortable with ffmpeg. Note that ffmpeg is also capable of video conversions of different formats and is a great tool. :)


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Linux Mint 14 "Nadia" RC Released

After 6 months of incremental development on top of stable and reliable technologies such as MATE, Cinnamon and MDM, Linux Mint 14 codenamed "Nadia" RC is available for download.

For the first time since Linux Mint 11, the development team was able to capitalize on upstream technology which works and fits its goals. After 6 months of incremental development, Linux Mint 14 features an impressive list of improvements, increased stability and a refined desktop experience. This new release comes with updated software and brings refinements and new features to make your desktop even more comfortable to use. Linux Mint 14 "Nadia" is based upon the Ubuntu 12.10 "Quantal Quetzal".



The download links (torrents and direct both) are available at this blog post.

Useful Links

Download Nadia
Nadia release notes
Whats New in Nadia


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Make Your Linux Read Papers For You

Fed up of reading text files and PDF papers? Is you eye power degrading day by day and can't hold even few minutes on screen? Don't worry, you can easily make your linux system speak and read all those papers for you.

There are several text to speech tools available for linux but in this post, I will be using festival, a Text-to-speech (TTS) tool written in C++. Also, Ubuntu and its derivation are most likely to include by default espeak, a multi-lingual software speech synthesizer.

For ubuntu and debian based system, type the following to install festival:

samar@samar-Techgaun:~$ sudo apt-get install festival

Moreover, you can also install a pidgin plugin that uses festival:

samar@samar-Techgaun:~$ sudo apt-get install pidgin-festival

For now, you just need to install festival. Once you have installed festival, you can make it read text files for you. If you go through the online manual of festival, it says:
"Festival works in two fundamental modes, command mode and text-to-speech mode (tts-mode). In command mode, information (in files or through standard input) is treated as commands and is interpreted by a Scheme interpreter. In tts-mode, information (in files or through standard input) is treated as text to be rendered as speech. The default mode is command mode, though this may change in later versions."

To read a text file, you can use the command below:

samar@samar-Techgaun:~$ festival --tts mypaper.txt

The festival will start in text-to-speech (tts) mode and will read your text files for you. But now, we want to read PDF files and if you try to read PDF files directly (festival --tts paper.pdf), festival is most likely to speak the cryptic terms since it actually reads the content of PDF including its header (You know PDF is different than simple text file). So we will use a pdftotext command to convert our pdf file and then pipe the output to the festival so that festival reads the PDF files for us. You can use the syntax as below to read PDF files.

samar@samar-Techgaun:~$ pdftotext paper.pdf - | festival --tts

If you want to skip all those table of contents and prefaces or if you are in the middle of PDF, you can use the switches of pdftotext to change the starting and ending pages. For example, if I wish to read page 10 - 14 of a PDF, I would do:

samar@samar-Techgaun:~$ pdftotext -f 10 -l 14 paper.pdf - | festival --tts

Enjoy learning. I hope this post helps you ;)


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CodeWeavers Announces Free CrossOver Giveaway

CodeWeavers, the developer of CrossOver has decided to run a 24-hour free giveaway for their famous wine-based product, CrossOver.

CrossOver allows you to install many popular Windows applications and PC games on your Linux computer. It's easy, affordable, and best of all, there's no Windows license required. Your Windows applications and games integrate seamlessly on your computer; just click and run. CrossOver is capable of running a wide range of Windows software and games.



On Wednesday, Oct. 31, 2012, beginning at 00:00 Central Time (-5 GMT), anyone visiting CodeWeavers’ Flock The Vote promotional web site (flock.codeweavers.com) will be able to download a free, fully functional copy of either CrossOver Mac or CrossOver Linux. Each copy comes complete with 12 months of support and product upgrades. Upon registering your name and e-mail address along with your version (CrossOver Mac or CrossOver Linux), you will get an e-mail with the instructions for download. The offer will continue for 24 hours, from 00:00 to 23:59, Oct. 31, 2012. Flock The Vote is an initiative to get more Americans to vote in the upcoming 2012 Presidential elections.

Get Free Copy Of CrossOver

Update: direct download links:

32 bit Debian/Ubuntu

64 bit Debian/Ubuntu

32/64 bit Red Hat (Fedora, SUSE, Mandriva)

Installer for all other linux distros

Mac and Others

Sandy survivors, you can still get the offer from HERE.


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Steam for Linux Beta Survey Is Out

Lately, Valve Software, the vendor for steam has been showing lots of interest to develop games for linux platforms and offer linux users one of the best gaming experiences. Valve has today announced its survey for steam for linux beta.

Valve Software writes: We're looking for Linux gamers to install and test our new Steam for Linux client. We are primarily interested in experienced Linux users.



In order to take the survey, you need to first login with your Steam account to link your response with your Steam ID. Once you are ready for beta testing, you can login from this link. 1000 steam users will be chosen based upon the responses in the survey.

Steam community recently got its dedicated linux section and good for us, all these signs seem to indicate that Valve is trying to extend its market over the linux platform.


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Linux Cat Command Examples

Cat is a standard unix tool to concatenate and display the content of files. In this post, I will present some examples of cat command so that you can use them in your scenario.

The cat command displays the content of file on the standard output. If multiple files are specified, the contents of all files will be concatenated and then displayed on the standard output. Likewise, if no file is specified, it will assume standard input (keyboard input) as the input to the command. The Ctrl + d is the shortcut used to save the contents in the appropriate output placeholder specified and exit the cat command.

Print content of file in standard output

samar@samar-Techgaun:~$ cat workers.txt 
List of workers, designations & salary (in K):
Kshitiz Director 30
Bikky Manager  20


Abhis Sweeper  10
Rajesh Guard  12

Print line numbers

samar@samar-Techgaun:~$ cat -n workers.txt 
     1 List of workers, designations & salary (in K):
     2 Kshitiz Director 30
     3 Bikky Manager  20
     4 
     5 
     6 Abhis Sweeper  10
     7 Rajesh Guard  12

Print line numbers for non-empty lines only

samar@samar-Techgaun:~$ cat -b workers.txt 
     1 List of workers, designations & salary (in K):
     2 Kshitiz Director 30
     3 Bikky Manager  20


     4 Abhis Sweeper  10
     5 Rajesh Guard  12

Create a new file

samar@samar-Techgaun:~$ cat > newfile.txt
We can create text files
using cat command
once u finish writing,
press ctrl+d to save file
^d

Display content of multiple files

samar@samar-Techgaun:~$ cat workers.txt newfile.txt 
List of workers, designations & salary (in K):
Kshitiz Director 30
Bikky Manager  20


Abhis Sweeper  10
Rajesh Guard  12
We can create text files
using cat command
once u finish writing,
press ctrl+d to save file

Combine multiple files to new file

samar@samar-Techgaun:~$ cat workers.txt newfile.txt > concat.txt
samar@samar-Techgaun:~$ cat concat.txt 
List of workers, designations & salary (in K):
Kshitiz Director 30
Bikky Manager  20


Abhis Sweeper  10
Rajesh Guard  12
We can create text files
using cat command
once u finish writing,
press ctrl+d to save file

Append data to existing file

samar@samar-Techgaun:~$ cat >> newfile.txt 
New line added
^d
samar@samar-Techgaun:~$ cat newfile.txt 
We can create text files
using cat command
once u finish writing,
press ctrl+d to save file
New line added

Alternatively, you can use the syntax below if you wish to create new file combining the content of already existing file and standard input.

samar@samar-Techgaun:~$ cat newfile.txt - > myfile
thanks for everything
^d
samar@samar-Techgaun:~$ cat myfile 
We can create text files
using cat command
once u finish writing,
press ctrl+d to save file
New line added
thanks for everything

Another possibility is to combine two text files with data from standard input (keyboard) in-between the contents of these two text files.

samar@samar-Techgaun:~$ cat workers.txt - newfile.txt > myfile

----------------------------------

^d
samar@samar-Techgaun:~$ cat myfile 
List of workers, designations & salary (in K):
Kshitiz Director 30
Bikky Manager  20


Abhis Sweeper  10
Rajesh Guard  12

----------------------------------

We can create text files
using cat command
once u finish writing,
press ctrl+d to save file
New line added

Display $ sign at the end of each line

samar@samar-Techgaun:~$ cat -E workers.txt 
List of workers, designations & salary (in K):$
Kshitiz Director 30$
Bikky Manager  20$
$
$
Abhis Sweeper  10$
Rajesh Guard  12$

Display ^I sign instead of TABs

samar@samar-Techgaun:~$ cat -T workers.txt 
List of workers, designations & salary (in K):
Kshitiz^IDirector^I30
Bikky^IManager^I^I20


Abhis^ISweeper^I^I10
Rajesh^IGuard^I^I12

Display files with non-printing characters

samar@samar-Techgaun:~$ cat -v /bin/nc

In the example above, the non-printing characters are replaced with ^ and M- notation except for line breaks and TABs. This can be used to display the contents of binary files which would otherwise have shown gibberish text all over the console.

Show contents with tabs, line breaks and non-printing characters

samar@samar-Techgaun:~$ cat -A /bin/nc

The tab will be substituted by ^I, line breaks with $ and non-printing characters with ^ and M- notation. Actually, the -A switch is equivalent to -vET switch.

Supress/squeeze repeated empty lines

samar@samar-Techgaun:~$ cat -s workers.txt 
List of workers, designations & salary (in K):
Kshitiz Director 30
Bikky Manager  20

Abhis Sweeper  10
Rajesh Guard  12

Using -s switch, we can squeeze repeatedly occurring blank lines and replace all the adjacent empty lines with a single empty line in the output. This might be useful to reformat a file with several empty lines in-between (eg. cat -s workers.txt > formatted_workers.txt).

Display last line first

samar@samar-Techgaun:~$ tac workers.txt 
Rajesh Guard  12
Abhis Sweeper  10

Bikky Manager  20
Kshitiz Director 30
List of workers, designations & salary (in K):

It is the tac, not the cat that is doing the magic but just thought that this is the right place to make a note about this little known command.

Edit: Added here-doc examples. Thanks rho dai for pointing me this.

Parameter substitution using here-document strings

samar@samar-Techgaun:~$ cat > test << TEST
samar@samar-Techgaun:~$ I am $USER. My home is $HOME
samar@samar-Techgaun:~$ I came here from $OLDPWD
samar@samar-Techgaun:~$ TEST
samar@samar-Techgaun:~$ cat test 
I am samar. My home is /home/samar
I came here from /home/samar/Downloads

Command expansion example

samar@samar-Techgaun:~$ cat > test << TEST
samar@samar-Techgaun:~$ $(ls /)
samar@samar-Techgaun:~$ TEST
samar@samar-Techgaun:~$ cat test
bin
boot
cdrom
dev
etc
home
initrd.img
initrd.img.old
lib
lost+found
media
mnt
opt
proc
root
run
sbin
selinux
srv
sys
tmp
usr
var
vmlinuz
vmlinuz.old

Parameter substitution turned off

samar@samar-Techgaun:~$ cat > test << 'TEST'
samar@samar-Techgaun:~$ I am $USER. My home is $HOME
samar@samar-Techgaun:~$ I came here from $OLDPWD
samar@samar-Techgaun:~$ TEST
samar@samar-Techgaun:~$ cat test
I am $USER. My home is $HOME
I came here from $OLDPWD

Note the difference between the last example and previous two examples. Enclosing the limit string TEST with quotes prevents the substitutions and expansions.

I hope these examples are useful. :)


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Ubuntu Studio - Ubuntu Derivation For Audio Video & Graphics Editor

Ubuntu Studio is a variant of Ubuntu aimed at the GNU/Linux audio, video and graphic enthusiast as well as professional. The distribution provides a collection of open-source applications available for multimedia creation. Ubuntu Studio is a free, open source and powerful operating system created for the creative people to create exceptional arts using right sets of tools for audio, video and graphical editing. As an officially recognized derivative of Ubuntu, Ubuntu Studio is supported by Canonical Ltd.

Ubuntu Studio is released every six months, but a long term release (LTS) version is released only every 2 years.

Audio apps include Jack, Ardour, Audacity, QTractor, Hydrogen, Yoshimi, Rakarrack, Gladish, Puredata and several other apps available for download.

Graphical apps include Blender, Inkscape, GIMP, MyPaint and several other apps.

Video apps include Openshot video editor, FFMPEG, DVDStyler, and other apps.

Photography apps include Darktable, Shotwell, and several other useful apps.

Calibre, Scribus and LibreOffice and other apps are available to suffice publishing needs.

Useful Links

Ubuntu Studio HOME

Ubuntu Studio Download

Ubuntu Studio Documentation


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Practical ls Command Examples For Fun & Profit

The power of linux lies in the shell through which we can perform complex job in no time. While the directory listing command 'ls' seems to be very simple command, the linux shell provides the power to use switches and pipes to do anything from terminal. Check out this list with practically useful examples using ls.

Display all files including hidden files/folders

ls -a

Display one file/folder per line

ls -1

Count number of files & folders

ls -1 | wc -l

Human readable file sizes (eg. Mb or Gb)

ls -lh

Alphabetically sort the listing

ls -X

Only list the folders in current directory

ls -d */
ls -p | grep /

Display folders in current directory consisting certain patterns

ls -l D* | grep :$
ls -l *a* | grep :$

List files by descending order of modification time

ls -lt
ls -l --sort=time #alternative long version

List files by descending order of creation time

ls -lct

List files in reverse order

ls -ltr
ls -l --sort=time --reverse #alternative long version

List files in descending order of file size

ls -lSh
ls -lh --sort=size
ls -lSh1 *.avi #find largest AVI file
rm `ls -S1 | head -1` #delete largest file in current folder

List files in ascending order of file size

ls -lShr
ls -lh --sort=size --reverse #alternative long version

Display directories in recursive manner

ls -R

Display the files/folders created today

ls -l --time-style=+%F | grep `date +%F`

Display the files/folders created this year

ls -l --time-style=+%y | grep `date +%y`

Any more example that fires up in your mind? Feel free to share over here ;)


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Useful Nautilus Shortcuts

Nautilus is a default file manager for GNOME Desktop and is used as the default file manager in several linux distros such as Ubuntu. I love nautilus because its simple, friendly, and clean, supports local as well as remote file systems over different protocols. Moreover, there are several useful shortcuts that make life easier while using nautilus.

Below is the list of the most helpful shortcuts for navigation and file management in the nautilus:

Ctrl + r: Refresh the current view

Ctrl + h: Toggle show/hide mode for hidden files

F9: Show/Hide the side pane

Ctrl + l: Activate location/url bar (You can then provide path to local or remote filesystems or quickly copy the absolute paths)

Alt + Up Arrow: Move up one directory level

Alt + Down Arrow: Move down one directory level (the directory to be entered should be selected for this to work)

Alt + Left Arrow: Go back to the previous folder in view

Alt + Right Arrow: Go forward

Ctrl + Shift + n: Create a new empty directory

Ctrl + (+ / -): Zoom in (+) or zoom out (-)

Ctrl + 0: Zoom to normal state

Alt + Enter: View selected file/folder properties

F2: Rename selected file/folder

Ctrl + Shift + Drag file/folder: Create symbolic link to file/folder

Ctrl + f: Search for files/folders

Ctrl + s: Select files based upon templates (eg. select all pdf files using *.pdf)

Ctrl + 1: Toggle view as icons

Ctrl + 2: Toggle view as lists

Ctrl + 3: Toggle compact view

Ctrl + w: Close current nautilus window

Ctrl + Shift + w: Current all open nautilus windows

Ctrl + T: Open new tab

Alt + HOME: Navigate to HOME folder

F6: Toggle between side pane and central pane

Know more shortcuts? Share as the comments :)


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How To Exclude Directory While Compressing With Tar

Quite a handy and useful tip here. Several times, you want to compress files and folders but there might be cases when you want to compress your data excluding some of the directories. Tar command makes the process easier by providing us a exclusion switch.

I was actually backing up data I had downloaded in the remote server and wanted a copy of backup tar file in my system as well. But all those images that resided in the folders deep inside were not necessary for me. So all I did was something like below:

adm@RServ:~$ tar cvf backup.tar test --exclude=image*

The above command effectively excludes all the sub directories from testdirectory having the string image (eg. image, images, images_old in my case) and creates the backup.tar file. Moreover, the --exclude switch also co-operates the regular expressions so you can specify the regex to filter the directories. As an example, the command below excludes the directories a, b, c, d, and e while creating the tarball.

adm@RServ:~$ tar cvf backup.tar test --exclude=[a-e]

You can exploit this switch for ease several times in your daily works. I hope this helps :)


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Binary, Hex, Octal and Decimal Conversion Under Linux

Base conversions are easy with linux CLI. No need of fancy GUI-based calculator to perform base conversions when there is our favorite linux terminal.

We will be using bc, a calculator language that supports arbitrary precision numbers with interactive execution of statements. We will exploit the pipelining feature of shell and will let the bc process our query to convert the numbers from one base to other.

From binary to decimal

The syntax is obvious and we will follow the similar syntax for all the conversions. In this first example, we are converting the binary number 1101101 from input base binary to decimal(obase defaults to decimal unless specified).

samar@samar-Techgaun:~$ echo "ibase=2;1101101" | bc
109

From octal to decimal

samar@samar-Techgaun:~$ echo "ibase=8;1101101" | bc
295489

From Hexadecimal to decimal

samar@samar-Techgaun:~$ echo "ibase=16;A1F3DF" | bc
10613727

From N-base to decimal

All you need to do is provide the appropriate ibase value (eg. ibase=4 for 4-base to decimal conversion).

samar@samar-Techgaun:~$ echo "ibase=16;A1F3DF" | bc
10613727

As seen in all the examples above, the conversion to decimal numbers does not require you to specify the obase as obase defaults to decimal. The same thing applies for ibase i.e. ibase defaults to decimal base by default as seen in the examples below.

Now lets try some conversion with decimal numbers as the input base.

From decimal to binary

samar@samar-Techgaun:~$ echo "obase=2;109" | bc
1101101

From decimal to octal

samar@samar-Techgaun:~$ echo "obase=8;295489" | bc
1101101

From decimal to hexadecimal

samar@samar-Techgaun:~$ echo "obase=16;10613727" | bc
A1F3DF

From decimal to N-base

All you need to do is provide the appropriate obase value (eg. obase=4 for decimal to 4-base conversion).

samar@samar-Techgaun:~$ echo "obase=4;121" | bc
1321

Below are few more examples of base conversions to clarify the use of the command.

From binary to octal

samar@samar-Techgaun:~$ echo "ibase=2;obase=8;1111" | bc
17

From hexadecimal to binary

samar@samar-Techgaun:~$ echo "ibase=16;obase=2;AFBE" | bc
1010111110111110

I hope this is helpful ;-)


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