Chasing Your ‘Tail’ With Linux

‘GNU tail’ is a small utility which prints (by default) the last 10 lines of any file. This an amazing piece of software not only allows you to see the last part of a file but also enables you to monitor a file’s changes without opening the file.

‘tail’ can be used alone or can be combined with other commands like ‘grep’, ‘ls’ etc.

To use ‘tail’, let’s first create a text file. You can create the file by issuing following command in terminal;

touch my_file

Now open my_file with your favorite text editor (nano in my case) and write some lines. For this article, I have written the following 15 lines;

this is the 1st line
this is the 2nd line
this is the 3rd line
this is the 4th line
this is the 5th line
this is the 6th line
this is the 7th line
this is the 8th line
this is the 9th line
this is the 10th line
this is the 11th line
this is the 12th line
this is the 13th line
this is the 14th line
this is the 15th line

Now issue the following command in terminal;

tail my_file

It will print the last 10 lines which would be the “this is the 6th line” through “this is the 15th line”.

You can control the number of lines which ‘tail’ will print. You can either increase or decrease the number of lines. For example, if you want ‘tail’ to show only last 3 lines, you can do this by issuing the following command;

tail -n 3 my_file

Now it will print only last 3 lines. You can use any number of lines instead of 3. Or you can use a plus sign like;

tail -n+7 my_file

‘tail’ will start printing from 7th line to the end of the file.

You can view the desired file with respect to size. Issue the following command in terminal;

tail -c 14 my_file

And it will show the output of last 14 bytes. In my case, the output was;

the 15th line

‘tail’ not only displays the static output of a file but it can also monitor the file for changes. A ‘-f’ option is used with ‘tail’ and it starts acting like a monitoring tool which not only displays the last few lines but also constantly updates the output as the file changes. Here is a very popular example;

tail -f /var/log/message

‘tail’ will print the last 10 lines of ‘message’ file. If you now plug-in you USB stick, you will notice that the change in ‘message’ file will instantly be reported by ‘tail’. To release the cursor press Ctrl+c.

There are many other useful options which you can use with ‘tail’ like;

tail -q my_file        # never output headers
tail -v my_file        # always outputs headers

You can combine ‘tail’ with other utilities like ‘ls’, ‘grep’, ‘head’ etc.

You can combine ‘tail’ with ‘grep’ to get lines with some specific ‘word’.

tail -n 5 my_file | grep 14

It will print only those lines out of last 5 which contains the word ’14’. In my case the output was:

this is 14th line # ’14’ will be highlighted

‘tail’ can also be combined with ‘ls’ to get the list of last few files/folders. For example, if you issue the following command;

ls -l | tail -n 2

It will give a long listing of files/folders but will show the last 2 entries of the working directory.

These are just two examples of combining ‘tail’ with other utilities. There are countless examples of combination of ‘tail’ and other softwares.

‘GNU tail’ is a very handy tool. It can output any amount of data depending upon the options used. It makes the work of an ordinary user much easer and helps him/her find information in files more efficiently. To become an expert in Linux, this is a mandatory utility over which a user must have complete mastery. Hopefully, this tutorial gets you started chasing your tail!

Using ‘Alias’ in Linux

There comes a time in every Linux users’ life when you will open the Terminal more often than not because you have realized that it is faster, more efficient and more powerful than GUI (Graphical User Interface).  You’ll have started to learn more and more commands and now feel more comfortable with command prompt.  The command prompt is all about commands – short commands as well as long commands.  If you are like me then you may not like to type the long commands (or even small commands) :)

You may be thinking about some way to avoid typing commands over and over. Enter the ‘alias’.

The ‘alias’ tool is a way to make the complicated things simple (and simple things simpler). You can use ‘alias’ instead of long (or even short) commands.  Now let’s see how the ‘alias’ works.

‘alias’ can make difficult and lengthy commands easy. The general format of ‘alias’ is:

alias Any_Word=”Command”

It means you linked an existing command to a (New) Word. This ‘Any_Word’ may contain anything – any alpha-numeric symbol, ‘Any_Word’ as well as ‘Command’ are interchangeable and can be used for the same purpose.

Simple Commands Made Simpler

As an example, ‘ls -l’  is used for listing directory contents in ‘long listing format’. This ‘ls -l’ can be replaced with a simpler alias. You can set the ‘alias’ for ‘ls –l’ as follows:

alias ll=”ls –l”

Now you just have to type ‘ll’ (without quotes) to get ‘long listing format’.

Or if you frequently misspell ‘ls’ as ‘sl’ and don’t want to install ‘sl’ package, then, you can use the following alias:

alias sl=”ls”

Now, whenever you type ‘sl’ in terminal, it will give you same results as ‘ls’.

Now consider even simpler example. To close a Terminal (or logout), you have to type ‘exit’ in Terminal. This ‘exit’ command can be made even simpler by using the following ‘alias’:

alias x="exit"

Now, you only have to type ‘x’ in Terminal to ‘exit’

Other examples of ‘alias’ are:

alias cp="cp -iv"
#make copy operation interactive and verbose
alias rm="rm -iv"
#make remove operation interactive and verbose
alias mv="mv -iv"
#make move operation interactive and verbose

Make Package Management A Bit Simpler

If you use Debian (or its derivatives) then you will be familiar with APT.  It is an excellent package manager.

In Ubuntu, to install software using APT, you have to use the following command:

sudo apt-get install <sofware_name>

It is a long command and consumes a lot of your time and energy :)

You can shorten this command by using ‘alias’.  Issue the following command in Terminal:

alias Install=”sudo apt-get install”

You can obviously use your own word instead of ‘Install’.

Now, you just have to type:

Install <software_name>

to install the (same) software. Simple, isn’t it?

You can simplify other aspects of APT. For example, you can use the following ‘alias’:

alias Remove=”sudo apt-get remove”

to uninstall a software.

Some other examples of attaching APT with ‘alias’ are:

alias Update=”sudo apt-get update”
alias Upgrade=”sudo apt-get upgrade”
alias Search=”apt-cache search”
alias Autoremove=”sudo apt-get autoremove”
alias Autoclean=”sudo apt-get autoclean”
alias Purge=”sudo apt-get remove –purge”

and so on…

A Very Interesting ‘alias’ For A Difficult Keyboard Button

On some keyboards, the dot (.) button is at very difficult position and if you have to use it more than once, it becomes even more difficult.  That’s why ‘cd ..’ is the command which I mistype the most.  This complication can be easily removed by using following ‘alias’ (you can use any other word instead of a dot):

alias .=”cd ..”
alias ..=”cd ../..”
alias ...=”cd ../../..”
alias ....=”cd ../../../..”

Using Internet From Terminal

If you regularly use lynx to browse the internet in terminal then you have to type long urls with lynx to visit the web pages.  You can simplify these long urls by using ‘alias’:

alias Google=”lynx http://www.google.com/”
alias Yahoo=”lynx http://www.yahoo.com/”
alias yalb =”lynx http://linux-blog.org/”

and so on…

Now just type Google, Yahoo or yalb to visit the respective web sites.

Simple ‘alias’ For More Complicated Commands

Long commands are not only difficult to remember but also take more time to type; when you have to use them on daily basis, you become frustrated when typing them again and again and again… So, ‘alias’ are more suitable for long and complicated commands.

Let’s consider an example.

To find the top 10 largest files in your system, you can set the following ‘alias’:

alias top10files=”find . -type f -exec ls -sh {} \; | sort -n -r | head -10”

You can even mix different commands with ‘alias’.  For instance, if you regularly use ‘tail’ and direct its output to file to later view that file, you can set a very simple ‘alias’ to do this cumbersome operation in 1 word:

alias Tail=”tail /var/log/messages > hello.txt;cat hello.txt”

Now just enter ‘Tail’ and viola! All is done at once.

You can use any file with tail and direct its output and you can even use ‘nano’ or ‘vi’ to view/edit its output.

Here’s another example… ‘alias’ to connect to a remote server:

alias any_name=”ssh <remote_server_address> -l <username> -p <port>”

You can even create ‘alias’ for your bash scripts, like:

alias clc=”sh /home/user/myscripts/calc.sh”

Now that you have set a few different ‘alias’  you might want to check that which ‘alias’ are set on your system.  To do that, just issue the following command:

alias

and it will list all the set ‘alias’ you have.

To remove an ‘alias’, just issue the ‘unalias’ command, like:

unalias Google

and now typing Google in terminal will do nothing (as it was set with lynx).

To remove all the ‘alias’, issue the following command and all the ‘alias’ are gone:

unalias –a

We have discussed the way of setting the ‘alias’ for different kinds of commands.  But setting ‘alias’ in this way be temporary.  When you reboot you PC, all the ‘alias’ which you have set will be gone.  This does not mean that you have to set all the ‘alias’ every time you boot your PC.  If you have set an ‘alias’ and you liked it so much that you want it to permanently reside in you PC, just add this alias in ‘.bashrc’ file in you home directory. For example, if you want ‘alias’:

Install <software_name>

to permanently reside in your PC then user your favorite text editor and add the following line in your ‘~/.bashrc’ file:

alias Install=”sudo apt-get install”

Now this ‘alias’ will not vanish into thin air when you reboot your PC. Only those ‘alias’  which are listed in ‘~/.bashrc’ file will be permanent.

This guide is just a preview about ‘alias’.  It is just about basic ways of using ‘alias’ to make your life simpler.  ‘GNU alias’ is a tool which can simplify your life immensely.  But unfortunately this tool is not given the attention it deserves.  In short, it is such a powerful tool that if you give it proper time, it can make you forget typing :)

New Linux with an Old Laptop: Fedora Core 4


Guest Editor Apostasy has decided to take a look at current distributions and how they perform and install on an older laptop. This article is the first in a series of many that will look at distributions such as Suse 10, Fedora Core 5, Mandriva, and other desktop-centric distributions.


The Hardware

  • Compaq Armada E500 Laptop
  • 700MHz Intel Pentium III
  • 256MB PC133 SDRAM
  • ATi Rage Mobility
  • Intel Ethernet Pro 100
  • Toshiba 10GB Hard Disk
  • Netgear WG511 Wireless PCMCIA Card

Installation

I chose to use a network install via HTTP. This went quite smoothly, initially via a text interface for configuring the network and entering the address to install from, then a graphical interface for partitioning and package selection. Right from the start Fedora looks like a professional O/S, it’s not fluffy and cute, but it is very pleasant to look at. Partitioning was handled automatically by Disk Druid, no problems at this stage.

Read more

Enlightenment 17 Review

My first Linux experiences came through Knoppix and Mandrake, which send you to the KDE desktop by default. I used KDE at first, but I wanted to experiment with other less Windowsesque environments. The first one I installed was Enlightenment 16, which I must confess I had first heard of in Neal Stephenson’s essay “In The Beginning There Was the Command Line.” In that essay he said Enlightenment “may be the hippest single technology product I have ever seen” and that “it looks amazingly cool.” Since these sentiments were written in 1999, plenty of rivals have emerged for the title of “hippest tech.”

Once I had Enlightenment installed on my laptop there was no going back. I tried out a few other window managers, but the efficiency of E16 was hard to beat. My only complaints were that Enlightenment seemed a bit short on conveniences such as launchers, so I ended up running GNOME stripped down to one panel and the main menu with E16 as the window manager. Meanwhile, I read the descriptions of the new “desktop shell” that the Enlightenment crew was working on, dubbed Enlightenment DR17 (or E17, as I’ll refer to it from here on) and thought it sounded like exactly what I wanted.

I should mention that “window manager” isn’t quite the right term for E17. The developers call it a desktop shell, intending it to fill in the space between a simple window manager like the original Enlightenment and a full-featured desktop environment like GNOME. In other words, they were setting out to create a desktop not unlike my own E16/GNOME hybrid. In this respect it does not disappoint.

In creating E17 the Enlightenment crew have created a set of shared libraries (the Enlightenment Foundation Libraries) with the goal of building a complete set of applications to create an integrated environment where all files and programs are readily available that remains fast and non-resource-intensive. Essentially, E17 breaks down a desktop environment into its essential components (window manager, file manager, launcher, main menu, etc.) and offers them as a completely customizable package, where the user chooses which elements to use at any time.

Early Impressions

When I started using E17 back in early May, I had already been a regular user of E16 for a while. My first impressions were that E17 sported some neat features, but configuring the menus (by making all those damn eapp files, E17’s special icon format — read on for more details) was a hassle, plus E17 was missing many of the small features, such as edge-flipping or icon boxes, that I liked in E16. But I stuck

run command

with it, updating it on a regular basis and reading the continually updated user guide at Get-E.org, and usability has steadily increased. Also, a number of the features I had been missing were added (like

window list

edge-flipping) or had been there all along (turns out there is an icon box module called ibox, which is disabled by default). A graphical eap creator and other additions like a run command, alt-tab window switching (complete with a well designed display) and, for those who use sloppy or mouse focus, automatic placement of the cursor in the newly selected window have improved general usability.

Read more

create an integrated environment where all files and programs are readily available that remains fast and non-resource-intensive. Essentially, E17 breaks down a desktop environment into its essential components (window manager, file manager, launcher, main menu, etc.) and offers them as a completely customizable package, where the user chooses which elements to use at any time.

Early Impressions