The output can be adjusted with command line switches to show only the current time. The time will be output in the format of the system locale by using the +%r switch, so the command will look like this:

Which gives the following output on my system:

So now that I can display the current time, I just need to figure out how to continuously update the information in order to create a terminal clock. I'm going to do that by using the echo command to display the output of the date command. By using some options with echo so that the output gets over-written, and placing that command in an infinite loop, I can display a simple clock in the terminal.

So here's the command:

Take note of the back-ticks around the date command. That tells the echo command to display the results of the date command. The "\\b" enters a backspace into the command and "\\c" tells echo not to enter a newline character. The number of \\b's needed will depend on the output time display format for your locale, so adjust this up or down as needed.

All in all, it's not that useful as most GUI based systems have a clock build in, but it provides a nice example of using an infinite loop as well as some of the special options available with the echo and date commands.

I've done a few different posts about re-encoding audio files. In my earliest one I showed how to re-sample a folder of MP3s to a lower bitrate using LAME. That process had the issue of losing the ID3 tags and required an ugly work around to partially solve the issue. I then some other posts showing how to convert a few different audio formats using GStreamer, but the process was neither generic or automated. GStreamer, however, does a great job of retaining  ID3 tags and other types of metadata, so it seemed like a good place to start with a new script.

GStreamer also has a great plugin that can determine what type of audio file is being input, so it can be used to make a fairly generic script that can handle most audio file types as input. The following script will convert all audio files in a folder to MP3 format. It will even re-encode/re-sample MP3's to the desired quality level. I've chosen to use variable bitrate encoding, but the GStreamer pipeline could be easily altered to do constant bitrate instead. You can increase or decrease the average bitrate of the output by adjusting the quality parameter in the pipeline.

#!/bin/bash

######################################################################
#                                                                    #
# NAME:            conv2mp3                                          #
# AUTHOR:          Linerd (http://tuxtweaks.com)                     #
# LICENSE:         CC BY 3.0                                         #
#                  http://creativecommons.org/licenses/by/3.0/       #
# REQUIRES:        GStreamer, GStreamer plugins (good, bad, ugly),   #
#                  lame                                              #
# VERSION:         1.0                                               #
# DESCRIPTION:     A program to re-encode audio to MP3 using         #
#                  GStreamer. This script will convert all audio     #
#                  files in a directory to MP3 format. The new files #
#                  will be placed in a sub-directory of the same     #
#                  name.                                             #
#                                                                    #
######################################################################

# Create a directory for the MP3 files
FILEDIR=${PWD##*/}
OUTDIR="$FILEDIR"

echo "Directory is: $FILEDIR"

# Check if conversion/resample directory exists and create it if it doesn't.
shopt -s nocasematch   # Make text evaluation case insensitive
if
   test -e $OUTDIR
then
   echo -e  "File/directory \e[4m$OUTDIR\e[0m already exists. Files may be overwritten - continue? (Y/n)"
   read REPLY
   if
     [[ "$REPLY" = "n" ]]
   then
     exit 1
   fi
else
   mkdir -p "$OUTDIR"
fi
shopt -u nocasematch  # Make text evaluation case sensitive again

# Set newline as the field separator
IFS=$'\n'

for FILE in `file * | grep udio | cut -d: -f1 | sed 's: :\\ :g'`; do
  echo "File name is: $FILE"
  NAME=${FILE%.*}  #Get file basename
  echo "Basename is: $NAME"
  EXT=${FILE##*.}  #Get file extension
  echo "Extension is: $EXT"
  echo
  echo "New file is $OUTDIR/$NAME.mp3"
  # GStreamer pipeline - use VBR quality setting. Range allowed 0-10 with
  # 0 being the best quality.
  gst-launch filesrc location="$FILE" ! decodebin2 ! audioconvert ! lamemp3enc target=quality quality=3 ! xingmux ! id3v2mux ! filesink location="./$OUTDIR/$NAME".mp3
done

exit 0

Save the above script as a file called conv2mp3 somewhere in your executable path. I suggest /home/yourID/bin. Then you need to make the file executable. You can probably do that with your file manager, or you can do it through the terminal like this:

Now you are ready to run the script. Using a terminal, navigate to the directory with the files that you want to convert. Then, just enter the command:

The script will then convert the files to MP3 and place them in a subdirectory with the same name as the one containing your original files. Here's a screen shot of my directory before running conv2mp3.

Here's what the same directory looks like after running conv2mp3.

And here's the subdirectory containing the new MP3 files.

The tarball is perhaps the most common way for program source code to be packaged for GNU/Linux systems.  The tar file can be used to package several files together in a single archive. That archive file can then be compressed with one of several compression algorithms.

Create a tarball

To create a tarball, it's good to have all of the files you want in the package to be contained in a directory. Although this is not necessary, it's convenient when you then go to extract the file later. That way the archive will be extracted to its own directory rather than dumping its contents into the current directory. You can then create a tarball from the command line like this:

In the above command, tar is followed by four command parameters:

• c: create an archive
• v: verbose output (list the files that are being processed)
• z: compress the archive with gzip compression
• f: use a file archive instead of tape. The f parameter is immediately followed by the name of the archive file to create, that's why it's the last parameter used.

 Extract a tarball

Extracting a tarball is done in a similar fashion to creating one. First you'll want to place the tarball file in a directory where you would like to extract it. If you would like to inspect the contents of the archive before extracting it, you can do so with this command.

The t parameter is what tells tar to list the contents of the file.

Once you've got the archive placed in the directory you want it, you can extract it with:

In the above command, the x parameter is used to tell tar to extract the archive. The rest of the parameters have the same meaning as they had when creating an archive.

More information

There are many more advanced options available for working with tar. You can read the entire manual by viewing the tar manpage.

Comments are now re-enabled.

Install LAMP

The Ubuntu development team has made it very easy to install and set up a web server. Open a terminal window and enter the following command.

Please enter the command exactly as it's shown above. The carat (^) is not a typo and the command will not work without it.

If prompted, enter your password.

The package manager will now display a list of packages to be installed. Hit <Enter> to confirm that you want to go ahead with the install.

Apt will now start downloading and installing the packages on your computer.

After a short wait, you will be prompted to set a password for MySQL's administrative user. Enter a password at the prompt and make sure it's something you will remember or make a note of it.

You will then be prompted to confirm your password.

Type in the same password and hit <Enter>. The package manager will now continue downloading and installing packages. After a short wait the installation will complete.

Testing Apache

Now we'll run a quick test to make sure that the Apache web server is working. Open a web browser and enter the address http://localhost/. You should see a page that says "It Works!"

Testing php

Now that we've verified that Apache works, we need to verify that php is working properly. We're going to create a file in the /var/www directory called testing.php. Enter the following command in the terminal to create the file.

Enter your password if prompted.

Now you'll need to restart the Apache web server. Enter into the terminal:

Now open your web browser and enter the following address: http://localhost/testing.php

You should see a web page that displays a bunch of information about your php and Apache environment.

Configure MySQL

Since this is for a local development environment, the MySQL database needs to be bound to the localhost IP address. This should be 127.0.0.1 by default. You can verify your localhost address with the following terminal command.

You should see output something like this:

127.0.0.1    localhost
::1     ip6-localhost ip6-loopback

Now you need to verify that this address is the bind address MySQL's my.cnf file. Use the following terminal command.

You should see output like this.

bind-address        = 127.0.0.1

If it's not correct you'll need to edit /etc/mysql/my.cnf as root to fix it.

Install phpMyAdmin

You now have a functioning LAMP installation. You don't need to install phpMyAdmin, but it provides a much easier way to administer your MySQL databases if you're not familiar with MySQL's commands. You can install phpMyAdmin with:

Enter your password if prompted.

Again the package manger will show you the packages it's about to install. Hit <Enter> to move forward with the installation.

The package manager will now begin downloading and installing packages. After a short wait you will be prompted to choose the web server to configure for phpMyAdmin. Hit <Space> to mark apache2 with an asterisk (*) as it's shown in the following picture (click on the image to see it in full size). Then hit <Enter>.

The next screen will ask about some automatic database configuration with dbconfig-common. Hit <Enter> to accept the default and move on.

Next you'll be prompted for the MySQL administrator password. Enter the password that your created earlier.

Now you'll be prompted for a MySQL application password. You can allow the system to generate a random password or choose your own.

If you choose your own password, you will be prompted to verify it at the next screen.

Your phpMyAdmin installation and configuration is now complete.

Testing phpMyAdmin

Open your web browser and enter the address http://localhost/phpmyadmin/.

You should see a page like this.

Now log in with the user name root and the password that you created earlier in the tutorial.

Congratulations, you now have a working web development environment set up on Ubuntu 11.10. You can place the files for your website under /var/www. Note that this location is owned by the root user, so you'll need to copy your files over as root for it to work. Otherwise, you can do some further Apache configuration so you can place the files for your website in a directory somewhere under your home directory.

Fixing some common problems

Fixing phpMyAdmin

One common error that some people make is that they forget to mark apache2 during the phpMyAdmin configuration. When this happens you'll get a 404 Not Found error when trying to navigate to http://localhost/phpmyadmin/.

If this happens, enter the following terminal command.

You will be prompted about reinstalling the database. Accept the default of "No" and hit <Enter>.

Make sure to then mark apache2 by having the cursor next to apache2 and then hitting <Space> to mark it with a *, then hit <Enter>.

You will then need to reload Apache.

You should now be able to load http://localhost/phpmyadmin/. If you're still seeing the 404 Not Found error, then you will need to clear your web browser cache and try again.

Fixing the Apache fully qualified domain name

During the above steps you may have seen an error message like this when reloading Apache.

apache2: Could not reliably determine the server's fully qualified domain name,
using 127.0.1.1 for ServerName

This doesn't seem to cause any problems for me, but if you don't like seeing that error, you can fix it with this command.

Then reload Apache with

Enjoy your new web development environment!

I'm going show the most basic use case for find: a search based on file name. In this form, the find command will be followed by a path telling where you want to search. You will then include the -name switch and specify a name pattern to match or a complete file name. If you use special characters in your pattern, like *, make sure to enclose them in single or double quotes. So the command is going to take the following form:

For the first example I'll show how to search for files with a .txt extension in your current directory and below. This command uses the built-in shortcut "." to specify the current directory.

Now you'll notice that the above command found all files with names that end in .txt in the current directory and all subdirectories. If you would like to limit the output to not include subdirectories, use the -maxdepth option.

Both of the above commands will find files that end in .txt, but not .TXT. If you'd like to find both, use the -iname switch instead of the -name switch.

There are many more options available with the find command. You can check it all out in the manual page.

As you can see, it's a powerful tool, but its true power really comes through when you want to perform a function on several files at once. You can use find to generate a list of files and then pipeline the output to another command to operate on those files.

One thing you can do is reinstall the package and then purge it from your system, but there's got to be a better way. Well, it turns out that you can use the dpkg command to do the job. You actually use dpkg twice: once to find the orphaned configuration files, and again to actually remove the files. The following command has been tested on Ubuntu 10.04 and 10.10, but it should work on any Debian or Ubuntu based Linux distribution.

You can view your distro's version information with the lsb_release command. To view all of the information available, use the -a switch.

This yields the following information when run on my netbook:

No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 10.10
Release:	10.10
Codename:	maverick

You can eliminate the field names by adding the -s switch for short output.

Which gives this as output:

No LSB modules are available.
Ubuntu
Ubuntu 10.10
10.10
maverick

Each field can also be extracted with its own switch as well;

• -i for Distributor's ID
• -d for Description
• -r for Release
• -c for Codename

For more information, check out the manual page for lsb_release.

From the email sent to subscribers:

We understand that many readers still prefer hard-copy magazines. But, we also have seen many long-standing, excellent publications either come to an end or grow very thin due to drastic increases in printing costs and decreases in print advertising budgets. We don't want either of those things to happen to Linux Journal, and we are making this change so we can continue delivering the quality content our readers enjoy. We have a core readership that has stuck with us -- and stuck with Linux -- for a generation. You, our readers, are at the very heart of Linux, and always have been. We want to keep that heart beating.

Oh well, I guess I'm not going to change their mind on this. Linux Journal is a great magazine for Linux enthusiasts and professionals alike. If you've never read it, now is your chance to check it out for free. As part of their digital only roll out, Linux Journal has made the September 2011 digital issue free. Hit the following link to view the September 2011 issue of Linux Journal.

I think you'll find it to be a quality publication.