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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Empty Trash From Command Line In Ubuntu

CLI is such a sexy piece so why bother using GUI, even for cleaning up your trash. In this post, you will see how you can empty trash in Ubuntu from command line.

The trash you see in GUI is nothing but just the view for the files deleted by users which are temporarily moved to the special location of user's home directory. For any user, the trash location is ~/.local/share/Trash/. That is, whatever a user deletes gets saved in this location.

samar@samar-Techgaun:~$ rm -rf ~/.local/share/Trash/

I hope this becomes useful :)


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Enable Fingerprint Authentication In Ubuntu

So you got fingerprint reader in your device but have not been able to use it under ubuntu? Follow this How To to enable fingerprint authentication in ubuntu using the Fingerprint GUI from fingerprints reader integration team.

First make sure your fingerprint hardware is supported. You can check for the vendor and device ID by entering the following command:

samar@TG:~$ lsusb | grep -i finger | awk -F " " '{print $6}'
138a:0005

This link provides the list of the supported fingerprint readers.

Installation is easy. Fire up the terminal and enter the following commands:

sudo add-apt-repository ppa:fingerprint/fingerprint-gui
sudo apt-get update
sudo apt-get install libbsapi policykit-1-fingerprint-gui fingerprint-gui

You will have to restart the system or log out the session and login back to use and configure the fingerprint GUI.

Press Alt + F2 and type fingerprint-gui. From this GUI, you can configure and enroll your fingerprints.

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Add Google Search Support In Gnome-Terminal

Gnome-terminal is my favorite thing in my system and recently I came to know that I could add google search support in gnome-terminal which is totally awesome. Ubuntu Tweak already includes the google search support but if you want google search in your terminal without the whole ubuntu tweak, you can follow this guide.

All you need to do is add the PPA and you can easily install the gnome-terminal with google search support. Fire up the terminal and enter the following commands:

sudo add-apt-repository ppa:tualatrix/personal
sudo apt-get update
sudo apt-get install gnome-terminal

Credits: Ubuntu Tweak


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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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Ubuntu 12.10 Beta 2 Released

The ubuntu developers have just released the Beta 2 of Ubuntu 12.10 Quantal Quetzal which gives the preview of the next version of ubuntu. The final ubuntu 12.10 release is scheduled for 18^th October this year. The Beta 2 release is intended to give the preview of how the final release of Quantal Quetzal will be like. The previous beta 1 release was released on 6^th September.

As always, Ubuntu has chosen the Quetzal as codename for Ubuntu 12.10. According to Wikipedia, Quetzals are strikingly colored birds in the trogon family. They are found in forests and woodlands, especially in humid highlands, with the five species from the genus Pharomachrus being exclusively Neotropical, while the single Euptilotis species is almost entirely restricted to western Mexico.

Like we heard earlier, Ubuntu 12.10 releases are no longer available as Live CD.

Download Quantal Quetzal 12.10 Beta 2 Release


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How To Find The Location Of Command In Linux

Sometimes you need to find the pathnames or locations of commands you use frequently. In this post, I am going to discuss two useful commands that are useful for locating Linux commands.

The first command to locate the Linux commands is which. This command returns the pathnames of the files or links. However, it does not follow the symbolic links.

samar@Techgaun:~$ which bash
/bin/bash

You can also find the pathnames of multiple commands at once using which command.

samar@Techgaun:~$ which -a bash cat ls iftop
/bin/bash
/bin/cat
/bin/ls
/usr/sbin/iftop

The other command is type command which is useful to determine if a command is an alias, a built-in command or an independent command.

samar@Techgaun:~$ type gedit
gedit is /usr/bin/gedit
samar@Techgaun:~$ type grep
grep is aliased to `grep --color=auto'
samar@Techgaun:~$ type -t iftop
file

You can play more with the type command. I hope this helps :)


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Ubuntu Desktop Edition No More In LiveCD

The ubuntu team has announced that they have dropped the LiveCD option for Ubuntu and now onwards Ubuntu will be available as a single 800MB image that can be used from USB or DVD.

The mailing list reads "For the client, this release now has a consolidated Ubuntu image. There is no longer a traditional CD sized image, DVD or alternate image, but rather a single 800MB Ubuntu image that can be used from USB or DVD. This change does not affect Ubuntu Server, which remains a traditional CD sized image.

That is, starting from Ubuntu 12.10 "Quantal Quetzal", we will have a single 800 MB disk image that can only be used with USB or DVD. The decision does not seem to affect Ubuntu's user base since DVDs and USBs are getting cheaper and LiveUSBs are being popular these days.


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Preventing Accidental Overwriting Of Files In Bash Shell

How many times has this happened to you? It used to happen once in a while with me. A Linux user learns to use the redirection operators such as '>' and '>>' but accidental overwriting starts to become common in commands you use and shell scripts you write.

The accidental overwriting of files that happens unintentionally is known as clobbering and it commonly happens while using the '>' redirection operator.

samar@Techgaun:~$ mycmd > myfile

In the above example, the mycmd clobbers any existing data in the myfile file if that file exists already. Worse things may happen sometime. Imagine accidentally typing

samar@Techgaun:~$ mycmd > /etc/passwd

instead of possibly using other redirection operators (like >> or <). Thankfully, you could recover /etc/passwd from either /etc/passwd- or /var/backups/passwd.bak if you hadn't rm'd these files.

To prevent such accidental overwriting, we can set the noclobber environment variable. Below is a session of enabling this variable:

samar@Techgaun:~/Desktop/test$ echo "www.techgaun.com" > myfile
samar@Techgaun:~/Desktop/test$ echo "Overwriting techgaun.com" > myfile
samar@Techgaun:~/Desktop/test$ set -o noclobber
samar@Techgaun:~/Desktop/test$ echo "Retrying to overwrite" > myfile
-bash: myfile: cannot overwrite existing file

As seen above, you have to turn on the noclobber variable using the set -o noclobber command in your shell. However, you might want to intentionally overwrite contents of certain files even when the noclobber is turned on.

samar@Techgaun:~$ mycmd >| myfile

Notice the >| in place of your normal > redirection operator. Using this operator, you can however overwrite the existing files even if the noclobber is turned on.

If you want to turn off the noclobber variable, type the following:

samar@Techgaun:~$ set +o noclobber

You can also permanently turn on the noclobber by the following command:

samar@Techgaun:~$ echo "set -o noclobber" >> ~/.bashrc

Moreover, such accidental overwriting can be prevented by enabling the interactive mode which is available in most of the linux commands. For example, you can write the alias for many commands that are likely to cause accidental overwriting. See some examples of aliases below:

samar@Techgaun:~$ alias rm=rm -i
samar@Techgaun:~$ alias mv=mv -i

You could even keep these aliases in your ~/.bashrc file permanently. Enabling such interactive modes by default in the commands that are more likely to cause accidental overwriting can prevent clobbering in many cases.

I hope this proves useful to you :)


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How To Search Manual Pages In Linux

Linux system consists of hundreds of binaries, several syscalls, and other stuffs that do have manual page. What if you want to locate or find the commands by searching through the manual pages? In this post, I am going to talk about one such useful command to search through the manual page names and short descriptions.

The command I am talking about is the apropos command. The best way to learn any linux command is to read its corresponding manual and go through the help (-h or --help) so lets poke through the help of apropos itself.

samar@Techgaun:~$ apropos -h
Usage: apropos [OPTION...] KEYWORD...

  -d, --debug                emit debugging messages
  -v, --verbose              print verbose warning messages
  -e, --exact                search each keyword for exact match
  -r, --regex                interpret each keyword as a regex
  -w, --wildcard             the keyword(s) contain wildcards
  -a, --and                  require all keywords to match
  -l, --long                 do not trim output to terminal width
  -C, --config-file=FILE     use this user configuration file
  -L, --locale=LOCALE        define the locale for this search
  -m, --systems=SYSTEM       use manual pages from other systems
  -M, --manpath=PATH         set search path for manual pages to PATH
  -s, --section=SECTION      search only this section
  -?, --help                 give this help list
      --usage                give a short usage message
  -V, --version              print program version

Mandatory or optional arguments to long options are also mandatory or optional
for any corresponding short options.

The --regex option is enabled by default.

Report bugs to cjwatson@debian.org.

Particularly, the -e switch is quite useful to filter out your search. See the example below:

samar@Techgaun:~$ apropos -e tar
bf_tar (1)           - shell script to write a tar file of a bogofilter direc...
bf_tar-bdb (1)       - shell script to write a tar file of a bogofilter direc...
git-tar-tree (1)     - Create a tar archive of the files in the named tree ob...
lz (1)               - gunzips and shows a listing of a gzip'd tar'd archive
mxtar (1)            - Wrapper for using GNU tar directly from a floppy disk
ptar (1)             - a tar-like program written in perl
tar (1)              - The GNU version of the tar archiving utility
tar (5)              - format of tape archive files
tgz (1)              - makes a gzip'd tar archive
uz (1)               - gunzips and extracts a gzip'd tar'd archive

Each command has its associated short description and the apropos command searches the short description section of appropriate manual page for the provided keyword. You can also specify the search keywords in the form of regular expression for more flexibility. I hope this command counts as useful one :)


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Ubuntu "Precise Pangolin" 12.04.1 LTS Released

After few months of release of Precise Pangolin, the Canonical and ubuntu developers have finally released the version 12.04.1 of Long Term Support (LTS) of Ubuntu for desktop, server, cloud and core products.

For your information, each new LTS version is released every 2 years. Starting with Ubuntu 12.04 LTS, both desktop and server versions will receive 5 years support. Earlier versions received 3 years support for desktop version and 5 years support for server version.

Among all the changes, the most notable one is the support for Calxeda ECX-1000 SoC family for supporting low-energy hyper-scale data centre servers.

The Ubuntu Cloud Archive also makes its debut - essentially an online software repository from which administrators can download the latest versions of OpenStack for use with the latest long-term support (LTS) release of Ubuntu.

Certified 12.04.1 Ubuntu Cloud images are now available on Amazon Web Services and will soon be posted to Windows Azure as well.

You can follow the detailed Release Announcement and Change Summary for Ubuntu 12.04.1 LTS.

You can download Ubuntu 12.04 LTS from HERE.


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Install XAMPP 1.8 From PPA In Ubuntu

Since apache friends has released the v. 1.8 of XAMPP for linux and windows, its important you guys upgrade your XAMPP. In this post, you will find the instructions to install XAMPP 1.8 from PPA.

The most important updates of v. 1.8.0 of XAMPP are: Apache 2.4.2, MySQL 5.5.25a, PHP 5.4.4, and phpMyAdmin 3.5.1. Since the software components are updated, I strongly recommend to upgrade your XAMPP.
All you have to do is follow the following steps in order:

sudo add-apt-repository ppa:upubuntu-com/xampp
sudo apt-get update
sudo apt-get install xampp

Alternatively, you can download the tar file for XAMPP from Apache Friends and follow their instructions to install XAMPP 1.8.0. In case you're looking for upgrading your previous XAMPP installation, be sure to follow this How To.

I hope this helps :)


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How To Manually Install Flash Player 11 In Linux

This post will provide a step by step instructions for installing flash player 11 plugin in ubuntu 11.04 and other different versions and distros. This will be helpful for everybody who are having trouble with the software center like I had.


Make sure no firefox process is running and then fire up the terminal and type the following commands in order:

mkdir -p ~/flash && cd ~/flash

wget http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_11.2.202.238.orig.tar.gz

tar -zxvf adobe-flashplugin_11.2.202.238.orig.tar.gz

sudo cp -r libflashplayer.so /usr/lib/firefox/plugins

sudo cp -r usr/* /usr

Once you have finished copying the shared object and other necessary files in their respective target directories, you can open the firefox and you're good to go. :)


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Screen Recording Software Solutions For Linux

Windows users have several options to choose from when it comes to the desktop recording (and only paid ones are good generally) but Linux users have fewer options but robust, simple, and best of all, free and open source desktop screen recording tools that we can trust on.

Below are some of the screen recording tools you might want to try:

recordMyDesktop

recordMyDesktop is a desktop session recorder for GNU/Linux written in C. recordMyDesktop itself is a command-line tool and few GUI frontends are also available for this tool. There are two frontends, written in python with pyGtk (gtk-recordMyDesktop) and pyQt4 (qt-recordMyDesktop). recordMyDesktop offers also the ability to record audio through ALSA, OSS or the JACK audio server. Also, recordMyDesktop produces files using only open formats. These are theora for video and vorbis for audio, using the ogg container.

Installation under debian and ubuntu:

sudo apt-get install gtk-recordmydesktop

XVidCap

XVidCap is a small tool to capture things going on on an X-Windows display to either individual frames or an MPEG video. It enables you to capture videos off your X-Window desktop for illustration or documentation purposes.It is intended to be a standards-based alternative to tools like Lotus ScreenCam.

sudo apt-get install xvidcap

Istanbul

Istanbul is a desktop session recorder for the Free Desktop. It records your session into an Ogg Theora video file. To start the recording, you click on its icon in the notification area. To stop you click its icon again. It works on GNOME, KDE, XFCE and others. It was named so as a tribute to Liverpool's 5th European Cup triumph in Istanbul on May 25th 2005.

sudo apt-get install istanbul

Vnc2Flv

Vnc2flv is a cross-platform screen recording tool for UNIX, Windows or Mac. It captures a VNC desktop session (either your own screen or a remote computer) and saves as a Flash Video (FLV) file.

Wink

Wink is a Tutorial and Presentation creation software, primarily aimed at creating tutorials on how to use software (like a tutor for MS-Word/Excel etc). Using Wink you can capture screenshots, add explanations boxes, buttons, titles etc and generate a highly effective tutorial for your users. It requires GTK 2.4 or higher and unfortunately is just a freeware(could not find any source code for it).

Screenkast

Screenkast is a screen capturing program that records your screen-activities, supports commentboxes and exports to all video formats.

If you got any more suggestions, please drop the comment. :)


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Determine Your SATA Disk Model And Vendor In Ubuntu

Sometimes you need to determine the model and vendor of your hard disk and here is the small tips on how to find those information.

All you have to do is type one of the following commands for the respective outputs:

cat /sys/class/block/sda/device/model

cat /sys/class/block/sda/device/vendor

I hope this becomes useful sometimes. :)


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Why Alias Command With Itself

Aliasing the command to itself to suppress the original functionality of the command and provide it new added sets of functionality can come quite handy for linux users and administrators.

If you have been using linux shell for a while, I'm pretty sure you are now familiar with the `ls` command, if not I think you have just learnt to use man pages. Probably you've been using `ls -l` command to list files with the files size as well. Too bad, you won't just be able to instantly make the sense of the file size displayed using this command so why not alias `ls` command to always provide human readable file sizes. So here is my alias:

alias ls='ls -lh'

This is what I always want to see as the output with `ls` command. The same kind of alias can be used with `du` and `df` commands. There are number of other cases where aliasing a command with itself is good choice.

Another example is the less command. By default, you need to press q to exit less which can be quite annoying if the entire content can fit in a single screen. However, adding -F flag will gracefully quit after displaying the content if the content fits in a single screen. So I have my alias for less as below:

alias lesss='less -F'

If something shoots in your mind, feel free to share here as a comment :)


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Stack-based Directory Switching For Easy Reversal

So how many times have you used the `cd` command repeatedly to go back and forth of two or more directories. Probably you are already familiar to the `cd -` command which lets you switch between the current and the previous directory. But, many times this current and previous directory switching restriction will not suffice and hence a better option in such case is to use the `pushd` command instead of `cd`.

For example, just use the `pushd somedirA`, `pushd somedirB`, ... and like that. Now if you need to switch back, you can just use `popd` command and you'll be switching back easily. The `pushd` command saves the current directory path and then cds to the supplied path.

If you dig more, you'll come to know about the -n and -N switches you can combine with these commands so I will let you explore on this. Also, you can use the `dirs` command to view the stack of directories. If you are some computer student or enthusiast, you have already gotten an idea from a famous data structure called stack. Anyway, I hope this comes handy sometimes like it does to me :)


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Fix "trying to overwrite '*', which is also in package *"

Today I was updating few stuffs in edubuntu and dpkg was continually throwing me the problem while trying to install kdelibs-data. The error read as "trying to overwrite 'A', which is also in package X" and the fix was pretty straightforward but still I thought it would help someone out there.

Below is the exact error I was getting while trying to install kdelibs5-data from the deb file.

dpkg: error processing /var/cache/apt/archives/
kdelibs5-data_4%3a4.4.5-0ubuntu1.2_all.deb (--unpack):
trying to overwrite '/usr/share/polkit-1/actions
/org.kde.kcontrol.kcmremotewidgets.policy', which is also in package kdebase-runtime-data 4:4.6.5-0ubuntu1

The fix was pretty simple. Add the --force-overwrite switch in the dpkg command as below:

dpkg -i --force-overwrite kdelibs5-data_4.4.5-0ubuntu1.2_all.deb

I hope this comes useful sometimes.


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How To Enable Use Of Htaccess In Apache In Ubuntu

This How To provides a detail on how to enable use of .htaccess file in apache in ubuntu and the similar flavors of linux distribution.

To enable use of .htaccess, you can edit the /etc/apache2/sites-available/default file. Search for the portion which contains the following lines or something similar to that(The bold line is almost always present):

<Directory /var/www/>
Options Indexes FollowSymLinks MultiViews
AllowOverride None
Order allow,deny
allow from all
</Directory>

All you have to do is change the bold line above to:

<Directory /var/www/>
Options Indexes FollowSymLinks MultiViews
AllowOverride All
Order allow,deny
allow from all
</Directory>

Now you will need to restart the apache service so that the effect of change in configuration takes place. Enter the following command to restart the apache service:

samar@Techgaun:~$ sudo service apache2 reload

Now your .htaccess files will start to work in ubuntu. :)


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