To copy, preserving permissions AND structure AND recursively, from a remote system to your local system:

rsync -r -a -v -e ssh server1.address.com:/dir/youwant/to/copy/ /local/location/for/directory/

Please note that the code above assumes that you are using key based authentication and not password.  For password based authentication, it would look more like this:

rsync -r -a -v -e ssh remoteuser@server1.address.com:/dir/youwant/to/copy/ /local/location/for/directory/

To remove all files matching a certain extension (xml in my example) in a directory:

find . -type f -name "*.xml" -exec rm -f {} \;

To go into a location, find all files that match a certain extension (jpg in my example) and move them to a different directory:

find . -name "*.jpg" | xargs -i mv '{}' /location/to/move/them/to/ 

To recursively remove empty directory from the directory you are currently in (your pwd):

find -depth -type d -empty -exec rmdir {} \;

These are a few of the commands that I’ve found useful in the past few weeks.  I hope you find them useful as well.  I’ll be test driving quite a few different distributions and reporting back what I find as well as experimenting with various different commands…I really like find because it is so powerful so look for some more posts with uses of the find command.  Thanks for reading and sorry for my lapse in posting this past month!

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Some Random Helpful Hints originally appeared on Yet Another Linux Blog on June 10, 2011.

‘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!

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Chasing Your ‘Tail’ With Linux originally appeared on Yet Another Linux Blog on January 27, 2011.

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

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Using ‘Alias’ in Linux originally appeared on Yet Another Linux Blog on December 23, 2010.

Most people use GUI tools to search for files.  They don’t realize that they can use command line tools to search for them as well! GNU ‘find’ is such like a tool which can not only search files but can even copy, move or delete these files on the fly.

So let’s see that how ‘find’ works.

Find Your Lost Files!

Let’s start from a simple example:

Suppose you want to search for a file named ‘master.txt’ in your home directory.

Open the Terminal and issue the following command:

find . -name “master.txt”

‘find’ will immediately show the results.  If ‘find’ does not show any result, this means that the file, in our case, ‘master.txt’, does not exist.  It is not always the case that you want to find something in you home directory.  The lost/desired file may be anywhere in your computer.  Suppose you want to find a file named ‘space-01.jpg’ and you only know that its located somewhere in /usr directory. You can find it by issuing following command in Terminal:

find /usr -name “space-01.jpg”

and ‘find’ will tell you that this is located under /usr/share/backgrounds.

Using Wildcards

Maybe you want to search for a file but you don’t know its exact name?  Don’t worry!  You can still locate the file using ‘GNU find’ and wildcard will help you in this regard. Wildcards are a way of searching files when you don’t know much about your desired file.

One of the commonly used wildcard is asterisk (*).  Lets consider an example to better understand the things.

Suppose you want to search a file named ‘Jumping_Flowers’ but you only remember the ‘Jumping‘ part of the file name.  So issue the following command in Terminal:

find . -name “Jumping*”

And it will display all the files starting with the word ‘Jumping’.  You can use asterisk (*) anywhere with a file name.  For example:

find . -name “*Jumping*”

And it will display all the files which contains the word ‘Jumping’.

Here are some more examples of use of a wildcard:

find . -name “Jumping*Flowers*”

find . -name “*Jumping*Flowres.mp3”

Searching For Different File Types

Sometimes you are not looking for some specific file but you are looking for a group of files.  For example, you may be looking for all the .txt files in your home directory.  To find all the .txt files, you will give the following command in Terminal:

find . -name *.txt

In case of mp3 files, the above command will be:

find . -name *.mp3

When You Want to Search with Respect to Time

If you want to search for files by the last time they were accessed, you can use -amin flag with ‘find’.  In this case you have to put a minus (-) sign before the time.  The time here is in minutes.  In order to search for .doc files which were accessed in last 10 minutes, you will give the following command:

find . -amin -10 -name "*.doc"

Similarly, to search for .doc files which were modified in last 20 minutes, you will use -mmin option as follows:

find . -mmin -20 -name “*.doc”

Search For Files which are Eating Your Hard Disk

There may be files on your system which are not only huge in size but also located obscure places.  You may also may not know when they were last accessed.  You have to use -size option with ‘find’ to locate them.

Let’s see how we can do this:

find . -size +100M

It will list all those files which are greater than 100 Megabytes.  You can replace ‘M’ with ‘G’ (for Gigabyte) or with ‘k’ (for Kilobyte)

Copy, Move, or Delete Unwanted Files on the Fly

Copy – ‘find’ can also be used to copy or backup your files.  You can use ‘find’ to copy certain files from one location to other with one simple command.

Suppose you want copy all of your mp3 songs from your home directory to your Windows Partition.  Enter the following command in Terminal:

find . -name "*.mp3" -exec cp {} /path/to/Windows_Drive \;

And all of your mp3 files will be copied to the desired Drive/Folder.

Move – There may be situations that you quickly want to move all of your document files from your Hard Disk to your USB to keep them safe.  To move all of your documents from your home directory to your USB, you will issue the following command:

find . -name "*.doc" -exec cp {} /path/to/USB \;

Delete – Suppose there are a lot of .tmp files and you want to get rid of them at once.  Again ‘GNU find’ is at your service and does the work for you.  Issue the following in Terminal and all of the .tmp files are gone…

find . -name '*.tmp' -exec rm {} \;

Which Files are Owned by You and Which Are Not?

There may be a situation when you want to know that which files in some other directories (or even in your home directory) are owned by some other user of your computer.

Suppose there is another user named ‘blackstar’ with whom you are sharing your PC.  Now you want to know that which .doc files in Windows Directory is owned by this user ‘blackstar’.  You can do this by issuing the following command:

find /path/to/Windows_Drive -user blackstar -name “*.doc”

Just replace ‘blackstar’ with your username to search on your system.

Direct the Output of ‘find’ to a File

You can save the results of your ‘find’ command to a text file which will allow you to examine the results in detail at some later time (or to create playlist of your songs).  For this purpose a greater than (>) sign is used (referred to as “piping the command”).

Suppose you want to save the list of all the mp3 songs in your home directory to a text file (which you can later share with your friend), you can do this by:

find . -name "*.mp3" > mp3.txt

It will save the complete path to all of your mp3 songs in the file named mp3.txt.

Find, a Handy Command Line Tool

This article is basically directed towards new users of Linux which are not much familiar with command prompt. This is a small but comprehensive article about ‘GNU find’ . The man pages of ‘find’ list a huge number of options which are difficult to explain in detail in one small article. I tried to cover those option which are commonly used. Obviously, to know more about such a powerful tool , one has to visit its man pages again and again and spend a lot time with ‘find’

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GNU find – A Multidimensional Tool originally appeared on Yet Another Linux Blog on November 24, 2010.

find / -name 'pattern'

Really though, the power of find isn’t just in finding names of files but rather specific details about those files. For example, if you wanted to find files which are writable by both their owner and their group:

find / -perm -444 -perm /222 ! -perm /111

or perhaps find any file that’s been altered in your Download directory in the past 24 hours:

find /home/user/Downloads/ -mtime 0

As you can see, the find command is very versatile and can be used to find an array of different attributes of files.  There are times though where I’m just looking for something and I don’t want to have to wait for the command to scan the entire directory tree in order to track it down.  That’s where locate comes in with quick and simple results.

Using the Locate Command

Using the locate command can only be accomplished if you install the mlocate package.  Most major distributions have this available.  If not, head over to the mlocate homepage and install manually.  Once that is accomplished, you’ll need to manually run a command to index your filesystem with it…otherwise, you’ll have to wait for the command to run automatically as it registers with cron to do so on a system level.  Open an terminal and change to your root user, then execute the following:

updatedb &

This updates the mlocate database that indexes your files and forks it to the background (the ‘&’ forks it to the background).  You can now logout of the terminal as root and the process will quietly work in the background.

After the command completes, using mlocate is as easy as using the locate command:

locate firefox | less

The command above will look for all files with firefox in the name and pipe the command through less so you can use the spacebar or enter key to scroll the file buffer.  Of course, the reason we pipe it through less is because any file that resides in the ‘firefox’ directory will be reported in the output.  While this tool isn’t as granular as the find command, it is a quick way to track down paths, directories, and files you know should exist.  Since the data is indexed using the updatedb command (by cron) the results are very quick and the command does not have to scan through the filesystem to return the results.

There are plenty more advanced options via flags (such as following symbolic links, making search term case sensitive, and even using regexp).  See the man page for details on how each of these options work.  Play around with locate and see what you can do!  It’s a powerful and quick search command!

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Finding Files with locate originally appeared on Yet Another Linux Blog on September 7, 2010.

convert SMFPress.png -channel Alpha -threshold 80% -resize 120x120 thumbnail.gif

This did a quick, same-size conversion with little loss for me to display the thumbnail online.  For more information on the options I used and other options that I didn’t use, take a peek at the ImageMagick Online Help Page for convert.

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Convert PNG to GIF via Command Line originally appeared on Yet Another Linux Blog on November 6, 2009.

On some distributions, the system-wide /etc/DIR_COLORS* files are removed or not present.  This results in no colors being given inside of a terminal when looking for color directories and filenames.  If you find yourself in this boat, try the following command to re-populate this setting:

devnet-> cd ~/
devnet-> dircolors -p >.dircolors

This should create a default profile for colors for your session if it hasn’t been done or was accidentally removed.  For more information on the dircolors command try ‘man dircolors’.  Please also note that dircolors command uses the environmental variable LS_COLORS to set your session.

For more information on LS_COLORS and how it pertains to the terminal/shell/cli/prompt, there are a few blog posts that do an excellent job explaining here, here and here.

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Adding Color to Bash List Command Part II originally appeared on Yet Another Linux Blog on September 8, 2009.

devnet[~]$ cat ~/.bashrc
alias lll="ls -al --color"
alias ll="ls -l --color"
alias l='ls --color'<br />alias search='find . -name'
alias aterm="aterm -fg white -tr"
alias version='cat /etc/zenwalk-version'
alias dh='df -h'<br />export PS1='\u[\W]\$ '
export PAGER="most"<br />devnet[~]$

I don’t use those aliases much…others of you might do the ‘ll’ or ‘lll’ but it’s just not part of my routine.  So, I added in just after line 4 in the code above:

alias ls='ls --color'

You can do this a few different ways…with any command line editor like emacs, vi, or nano/pico. It’s really up to you. The easiest way for new users is to use a text editor:

devnet[~]$ mousepad ~/.bashrc

This will launch the mousepad text editor in XFCE. If you’re in Gnome, try gedit. If KDE, give kwrite a try. You should see something like the following window pop up for editing:

You should see in the picture above, I’ve added in the alias needed to make me comfortable.  After that, File >> Save.  You’re set!  Except, you may notice that when you type the command ‘ls’ there are no colors.  So what gives?  Well, we haven’t loaded our ./bashrc since we changed it.  You don’t have to logout and back in to get things to work though…you can do this right from the terminal:

devnet[~]$ exec bash

Now try giving the ‘ls’ command a try again and you should see that it is in color.  I know a lot of the more advanced Linux guys out there are probably saying, “why’d he waste a post on this!  It’s easy” and you’d be right for a majority of users out there…I hope that this post finds some new user out there that may be stuck for an answer on how to do this.  One final note on this as well: You will have to do this as the root user and change /root/.bashrc in order for your root user to also have color.  Thanks for reading!

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Adding Color to Bash List Command originally appeared on Yet Another Linux Blog on June 5, 2009.

head -n 96 filename.php | tail -n 1

This allows you to quickly display the 96th line of filename.php. Hope this helps someone like it has me.

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Read & Display Single Line of a File originally appeared on Yet Another Linux Blog on November 18, 2008.

man command | col -x -b  > command.txt

Where command is the Linux command man page you want to print/view.  From there, open up command.txt in your favorite gui text editor (gedit, kate) and you have a readable format that could be printed quite easily for reference.

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Print Readable Man Pages originally appeared on Yet Another Linux Blog on November 14, 2007.