The notify-send command allows you to display messages right on the desktop via the notification daemon. These messages are fairly unobtrusive, fit it with your desktop scheme, and are really easy to set up in your scripts. And in this article I am going to show you how you can add this little system for easy message pop ups.

Installation

The notify-send tool  is a part of the libnotify package. So to install this do the following:

1. Open up a terminal window.
2. Issue the command sudo apt-get install libnotify-bin.
3. Enter your sudo password.
4. Accept any necessary dependencies.

That’s it. You are ready to start using this handy command.

Usage

The basic usage for the command is:

notify-send OPTIONS MESSAGE

Figure 1

Let’s take a very simple example of popping up the message “Hello Ghacks” on the desktop. To do this you would issue the command notify-send “Hello Ghacks” and hit enter. When you do you will see a small message pop up at the bottom of your desktop as you see in Figure 1. Of course the appearance of this message will depend upon which desktop you are using. I am using GNOME Shell so mine will be a variation on those of you using standard GNOME.

Let’s add an image to the message (the image you see in Figure 1 is the default). To add an image you use the -i option. The image used must be a .png file. You can find plenty of these in the /usr/share/pixmaps directory. So I am going to use the GNOME logo to remind me to take a walk. The command would look like:

notify-send -i /usr/share/pixmaps/gnome-about-logo.png “Take a walk!”

Figure 2

And the message would look like the one you see in Figure 2.

When you use this command you will notice the messages don’t last very long. You can change that with the -t option. You can set this so the message stays up until the user tell it to go away (by clicking on it) or you can set it to remain in milliseconds. So let’s say you want to give yourself a message to take a walk and you want it to remain open for ten seconds. To do this the command would look like:

notify-send -t 10000 -i /usr/share/pixmaps/gnome-about-logo.png “Take a walk!”

Or, if you want that message to remain until you click it away, the command would look like:

notify-send -t 0 -i /usr/share/pixmaps/gnome-about-logo.png “Take a walk!”

Final thoughts

You can imagine how much easier it has now become to notify yourself when a script has finished. You no longer have to rely on email messages or hacked-up notifications. Linux has a nice, built-in notification system you can use in your scripting or your cron jobs to let you know the things you need to know.

Twitter is basically a way of posting short messages on the Internet comparable to SMS but publicly visible and permanent. It is possible to follow people so that their messages get automatically displayed in Twitter. That’s the basic concept which proved to be very popular.

Nested Twitter Replies [link]

Twitter users can post replies to messages which are by default just displayed like any other message meaning that they are not grouped together. The Nested Twitter Replies userscript takes care of that by grouping the original message and the replies together.

Twitter Trends Explained [link]

Twitter trends are topics of public interest that are displayed in the right sidebar of the profile page. This covers a wide variety of topics from technology to politics and environment. There is no explanation on the topic by default which is changed by Twitter Trends Explained.

Endless Tweets [link]

Twitter displays a limited amount of messages per page. Users need to click every time they want to view additional messages. The Endless Tweets userscript will automatically load the next batch of messages when the user reaches the end of the page.

Twitter Search Results on Google [link]

Displays Twitter messages in Google Search results effectively combining Twitter messages in Google Search.

TinyURL Decoder [link]

The TinyURL Decoder supports dozens of different url shortening services that are being used by Twitter users.

Twitpic Thumbnailer [link]

Many Twitter users post images to Twitpic and link to these images in their Twitter messages. This userscript allows Twitter users to preview the thumbnails of those images.

Twitter Live Updater [link]

The Twitter message pages do not get updated automatically which means that users need to refresh them manually to check for new messages. The Twitter Live Updater will refresh the Twitter pages automatically periodically.

Twitter Friends Bio at a Glance [link]

This userscript displays information including the bio, followers and following count that are usually only visible on a user profile page

Twitter2FB [link]

Updates the Facebook status with the Twitter status.

Verdict: The userscript’s website lists hundreds of Twitter scripts that have been designed to change, add or modify functions and features on Twitter. They can really enhance the Twitter experience for users who regularly write and read messages.

dmesg

When I have a problem (or when I am attaching a usb device) one of the first places I go is the dmesg command. The dmesg command prints out the kernel keyring buffer. The information you will get will be all of the information you do not see when your system is booting. This is a great place to get information (low level) on your hardware. On one of my laptops, I run dmesg and near the top I see:

Phoenix BIOS detected: BIOS may corrupt low RAM, working it around.
last_pfn = 0x7f6d0 max_arch_pfn = 0x100000
x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106
kernel direct mapping tables up to 38000000 @ 10000-15000
Using x86 segment limits to approximate NX protection
RAMDISK: 37c6a000 - 37fef4a2


From that I can tell I have a Phoenix bios. Pretty obvious. A little later I see:

Security Framework initialized
SELinux:  Initializing.
SELinux:  Starting in permissive mode

Now I know Security Enhanced Linux is starting, in permissive mode, at bootup. And even further on down the line I see:

CPU1: Intel(R) Pentium(R) Dual  CPU  T2390  @ 1.86GHz stepping 0d
checking TSC synchronization [CPU#0 -> CPU#1]: passed.
Brought up 2 CPUs
Total of 2 processors activated (7447.76 BogoMIPS)

The above shows me information about my CPU. Good to know.

The most important information you will probably get from dmesg is the information regarding attached USB devices. When you plug in a USB device you will need to know what special device this is attached to so you can mount it. This will occur at the bottom of the dmesg command output.

The output of dmesg is quite long and will scroll by very quickly. When I run this command I always pipe it through the less command like so:

dmesg | less

This way I can view the output one page at a time.

/var/log

This special directory is the Mac Daddy of information gathering. Fire up a terminal window and issue the command ls /var/log/ and see what it contains. You see, included in this listing, such log files and log directories as:

• boot.log – boot information
• cron – cron logs
• cups – directory of all printing logs
• httpd – Apache logs
• mail – Mail server logs
• maillog – The mail log
• messages – Post-boot kernel information
• secure – Security log
• Xorg.0.log – X Server log

You can see the listing of log files in the /var/log directory, but in order to actually read the log files you have to be the root user (or use sudo).

Viewing with tail

One of the handiest methods of viewing log files is using the tail command. What tail does is follow the running output of a log file. For instance if I want to follow my /var/log/secure log to watch for security issues I would enter the command tail -f /var/log/secure. The f switch tells tail to follow. If  you don’t add the f switch tail will just list the output all at once (as if you just issued less /var/log/secure.)

Final Thougths

There is so much information to be gained from reading log files. The Linux operating system makes reading log files easy, once you know which log file does what. Take a poke around /var/log to find out exactly what you have and where you need to look for the problem you are having.