With this little ascii animation you can enjoy an animated pseudo-screensaver even on your GUI-less server. It won’t boost your productivity, it won’t make you a better programmer or your web site run faster. But it could bring you a bit of “security through obfuscation” from those who want to try to log onto your physical GUI-less workstation. Let’s see how to install and use this little under water wonder.

Installation

This little gem can be install on nearly any Linux distribution. As long as you have Perl installed, you should be able to get this up and running in no time. Here are the steps you need to follow. I will assume you might want to test this on a normal GUI-fied version of Linux before you try it on your GUI-less server. So, let’s install.

The first portion of the installation will take care of any remaining dependencies that aren’t included in the standard Perl installation. For this installation, follow these steps:

1. Open up a terminal windows. If you are using a GUI-less server then just log in.
2. Change to the /tmp directory with the command cd /tmp.
3. Download the Terminal Animation package with the command wget http://search.cpan.org/CPAN/authors/id/K/KB/KBAUCOM/Term-Animation-2.4.tar.gz.
4. Unpack the Terminal Animation package with the command tar -zxvf Term-Animation-2.4.tar.gz.
5. Change into the newly created directory with the command cd Term-Animation-2.4/.
6. Build the makefile with the command perl Makefile.PL && make && make test.
7. Compile Terminal Animation with the command sudo make install

Now to install the actually asciiquarium application. Follow these steps.

1. Open a terminal window (again, if you are using a GUI-less server, just log in).
2. Change to the /tmp directory with the command cd /tmp.
3. Download the necessary package with the command wget http://www.robobunny.com/projects/asciiquarium/asciiquarium.tar.gz.
4. Unpack the asciiquarium package with the command tar -zxvf asciiquarium.tar.gz.
5. Change into the newly created directory with the command cd asciiquarium.
6. Copy the executable to the necessary directory with the command sudo cp asciiquarium /usr/local/bin.
7. Give the executable the proper permissions with the command sudo chmod 0755 /usr/loca/bin/asciiquarium.

Figure 1

It is time to test out the waters of asciiquarium. To do so open up your terminal window (or if using a GUI-less machine – log in) and issue the command /usr/local/bin/asciiquarium. When it runs it will look something similar to Figure 1 (but in animated form).

Now, you may be asking yourself how could this serve as a form of security? Simple. Even with a standard desktop distribution you can log into a virtual terminal (Ctrl-Alt-F2 – for instance), log in, and run the application. Your full screen will be filled with the asciiquarium and unless a user knows to either hit Ctrl-c or move back to your original virtual terminal, they won’t have the slightest idea what to do.

I have covered the gnome-terminal in a few ways (see my articles “Make gnome-terminal profiles work for you” and “Get to know Linux: gnome-terminal“.) These articles either is an introduction or deals with a specific aspect of the tool. This time around, I want to highlight a few different tips and tricks that can help to make gnome-terminal even more useful and user-friendly.

Change that title

When you open up gnome-terminal you usually will see the hostname and the current working directory. Sometimes this just isn’t much help. This is especially true when you have more than one terminal window open and you want to make sure you know which terminal you are working in. You can change this by clicking Terminal > Set Title. After you click this a small window will open where you can type the new terminal title. Once you save that title your gnome-terminal will display the configured title until you close and re-open the tool (upon reopening the title will revert to the default.)

Search the contents of an open file

The gnome-terminal tool includes it’s own search feature. With an open file you can search that file with a string by clicking Search a new window will appear where you can enter the conditions for your search. Those conditions are:

• Search for: This is the string you want to search for in your file.
• Mach case.
• Match entire word only.
• Match as regular expression.
• Search backwards.
• Wrap around.

This is a great way to help you work with larger configuration files such as smb.conf or httpd.conf.

Zoom in/out

There are reasons for zoom in and out. The biggest reason is accessibility. For those with vision impairments, zooming into the terminal window is a quick way to make the text in terminal large enough to see. To zoom use the following key combinations:

• Zoom in: Ctrl++
• Zoom out: Ctrl--

If you have trouble with the key combinations, click View > Zoom In or View > Zoom Out to control the zoom.

Switch dimensions

I’m not talking about switching from 2D to 3D (or d20). I’m talking about the size of your terminal. There are four pre-configured sizes you can easily switch to (for different usage.) If you click the Terminal menu entry you will see, near the bottom of the menu:

• 80×24
• 80×43
• 132×24
• 132×43

You can easily switch to one of those sizes by clicking on the size you want. When you open the terminal, it will open back to the default size.

Final thoughts

There you have just a fraction of the tips and tricks that can be pulled off with gnome-terminal. There are plenty more where that come from and we will re-visit this topic. Until then, enjoy the CLI!

But you don’t want to just know the very basics of the command. Like anyone who hopes to master the Linux operating system, you want to know the commands in all their glory. With that in mind, let’s take an in-depth look at the df command and see what we can get out of it.

Basic usage

To understand the non-basic usage of the df command you must first understand the basic usage. So, the basic usage of df is:

df [OPTION] FILE

Where [OPTION] is any one (or combination) of the available options and FILE is a file located on a specific disk or partition. Don’t get confused about this. If you specify a file you will not see how much disk space the particular file uses. What you will see is the disk usage of the disk or partition the file resides on. This is a bit confusing at first.

The possible options are:

• a – Include dummy file systems.
• -B – Use SIZE in blocks.
• –total – Produce a grand total.
• -h – Print sizes in human readable formats.
• -H – Print sizes in human readable formats, but use powers of 1000 and not 1024.
• -i – List inode information and not block usage.
• -l – Limit listing to local file systems.
• –no-sync – Do not invoke sync before getting usage information.
• -P – Use POSIX output format.
• –sync – Invoke sync before getting usage information.
• -t – Limit listing to file systems of TYPE.
• -T – Print file system type.
• -x – Exclude file system type.

Now, let’s piece some of these options together to make df really useful.

Figure 1

Figure 2

Obviously, the basic usage is df. When you use that command you will see something like you see in Figure 1. If you’re looking for a much easier to read output, you would issue the command df -h. That will display everything in human readable format (see Figure 2).

Now, let’s add the partition types to the listing. To do this you would issue the command df -hT. This output would be similar to that in Figure 2, only it would add a column for Type before the Size column.

Figure 3

If you have a need to know the size of dummy file systems (such as dev, usb, proc, etc) on your machine, you could run the command like df -ah. This will add rows to your listing that will look like that shown in Figure 3.

Figure 4

What if you want to see a grand total of the percentage of disk space being used across all of your drives? To do this, issue the command df –total and you will see a new line added to the output that looks similar to what you see in Figure 4.

Final thoughts

A little df fun to help you gather all the knowledge you need with regards to how much space has been taken up on your disks. There are plenty of other tools to help you get this (and more) information from the command line. We’ll deal with more of those later.

NOTE: Since each of the below command serves a different purpose, you might have to install a piece of software to get it working. If there is a piece of software not included in the base Linux installation, I will make not of it and how to install the software.

Monitor changing files in real time

This command is fairly useful to watch your file system as it changes. It is more useful in just watching where changing files and percentages of drive space are critical. The command uses watch, df, and ls like so:

watch -d -n 2 'df; ls -FIAt;'

The above command will refresh every 2 seconds and show you what is being changed on your file system.

Check your Amazon paid ranking

I am a writer of novels (Check out my work on Amazon.com) and frequently check my paid rankings on Amazon.com. By using the Linux operating system I am privy to the tools necessary to create a cron job to dump the rankings into a file for me to check. The command to do this makes use of wget, grep, cut, and sed and looks like:

wget -q -O - http://www.amazon.com/gp/product/XXXXXXXXXX | grep 'Paid in' | cut -d' ' -f1 | sed 's/[#,]//g' >> rank.log

Where XXXXXXXX is the code for the title you want to follow.

Check your unread Gmail email

Here’s a very handy command for those of you who use Gmail and would like to check for unread email without having to fire up a browser. This command makes use of: curl, tr, awk, and sed and looks like:

curl -u GMAIL_ADDRESS:GMAIL_PASSWORD --silent "https://mail.google.com/mail/feed/atom" | tr -d '\n' | awk -F '<entry>' '{for (i=2; i<=NF; i++) {print $i}}' | sed -n "s/<title>\(.*\)<\/title.*name>\(.*\)<\/name>.*/\2 - \1/p"

Where GMAIL_ADDRESS is your actual gmail address and GMAIL_PASSWORD is your gmail password. Upon successful authentication the sender and subject of your unread Gmail will be printed out.

Display a directory as a web page

This command is incredibly handy. Say you want to allow someone access to files quickly via a web browser on your machine. You can do that with the help of python. All you do is change into the directory you want to serve up and then run the command:

python -m SimpleHTTPServer

Now, whoever needs to view that page simply points their browser to http://ADDRESS_OF_MACHINE:8000

Where ADDRESS_OF_MACHINE is either the IP Address or Domain of the machine (whichever applies). The user will then be able to navigate the files and folders within the directory you are serving up.

I want to introduce you to a few of these handy, but little-known, Linux administration tools.

Figure 1

w

The w command is a very simple tool that displays to you who is logged onto a system, when they logged in, and what processes they are using. This command is incredibly simple to use, just issue the command w and you will receive output similar to that shown in Figure 1.

As you can see the user jlwallen (that’s me) has been logged in since 14:19 and has four processes running.

iostat

Figure 2

The iostat command (part of the sysstat program) will report CPU statistics and I/O statistics. As you can see, in Figure 2, iostat is broken into three sections:

Information: Information about kernel, hostname, date, and architecture.

Avg-CPU: This section gives you all of the information about your CPU on different levels (user, system, I/O, involuntary wait, and idle).

Device: This section offers statistics on a per physical device basis.

Figure 3

mpstat

The mpstat command will display a per-processor listing of processes. If you issue the command mpstat -P ALL you will see a listing of your processes for each CPU (see Figure 3). This command will report processes on a user, idle, nice, system, irq, involuntary wait, and guest level.

Instead of running this on all processors you can specify a processor with the -P argument.

Figure 4

pmap

This tool is more used for developers as it will report bottlenecks in memory. You have to use it on a process ID (PID) like so:

pmap -d PID

Where PID is the actual process ID of the program you want to check.

As I already mentioned, the information output from this command will be helpful for developers and not much more.

Figure 5

ss

The socket statistics command will give you output of all network sockets on your system. As you can see (in Figure 5) there are a lot of sockets to list on the average computer. This command is similar to netstat but is much faster at reporting. Figure 5 illustrates how ss does its reporting. Here you see localhost as well as some private IP addresses connecting to sockets on this particular machine.

Figure 6

iptraf

The iptraf tool is one of my favorite text-based network monitoring tools. You won’t find iptraf installed by default (it’s generally in the default repositories for distributions, so it’s easy to install). Once you have iptraf installed you can start it by issuing the command iptraf. This tool allows you to create filters which can monitor specific network devices, addresses, packets, ports, and more.

Conclusion

The Linux operating system offers a ton of administration tools. Since many of those tools are commands, they wind up disappearing in obscurity. Here you have seen a few of those obscure commands. If you need more information on any of these commands you can check out the man page for each.

What byobu really is is a wrapper script that that launches the GNU Screen application using the byobu configuration. The user will see a strip along the bottom edge of the terminal window that gives a real-time update on various processes. Let’s take a look at this handy tool and see what all it can do.

Installation

ISince this is a console based tool, I will show you how to install it from the command line. Here’s how it’s done:

1. Open up a terminal window.
2. Issue the command sudo apt-get install byobu (for Ubuntu) or yum install byobu (for Fedora). NOTE: For Fedora you will have to su to the root user prior to issuing the installation command.
3. Accept any dependencies that might be required.

Once the installation is complete, you are ready to begin using byobu.

Usage

Figure 1

To use byobu, just enter the command byobu from the command prompt. When you do you will see the small strip appear at the bottom of your terminal (see Figure 1).

Figure 1 does show the top command running in the terminal to distinguish between a terminal in use and the byubu portion of the screen. If you end the top command, you will be left with an empty terminal window save for the bash prompt and the byobu strip at the bottom.

Figure 2

The byobu interface will update in real time and can give you information regarding numerous systems or monitors. You can configure what you want byobu to monitor in the ~/.byobu/status file OR you can simply hit F9 while byobu is running. When you hit F9 you will see the byobu configuration window (see Figure 2). From this window you can configure a number of options. To set (or unset) the notifications you want, scroll down (with arrow keys) to the Toggle status notifications and hit Enter. When you do you will see a simple window that lists all the possible notifications for byobu. Move through the list with your arrow keys and then hit the space bar to select any option you want to include (or not include). Once you have completed this hit the Tab button to get down to the Apply “button” to save your changes. Those changes will be made as soon as you click Apply.

From the main configuration window you can also change a number of features such as fore and background colors, keybinding, escape sequence, and more. You can even add new shells (which are similar to tabs). Once you’ve added new shells you can more back and forth between the shells by hitting the F2 button to move backwards and F3 to move forward. You can  have any number of shells you want.

Final thoughts

The byobu tool is a very cool way to add extra functionality to the standard terminal window. If you are looking for a bit more from the standard Linux shell, byobu is just what you need.

That’s a cumbersome process, especially if you copy and paste contents from the command line on a regular basis. Microsoft did however add an option to the command line preferences to make this whole operation more comfortable and natural.

The so called Quick Edit Mode enables direct copy and paste operations in the command line. You need to perform the following steps to enable the mode:

How To Enable Quick Edit Mode

Open a command line prompt. you can either open one by pressing Windows-R, typing cmd and hitting enter, or by clicking on the start menu orb, then All Programs > Accessories > Command Prompt. Please note that the second option is valid for Windows 7, it may differ on other Windows operating systems.

Once the command line is open right-click the title bar and select Properties from the context menu. A new window called Command Prompt Properties opens. Switch to the Options tab there and locate the entry Quick Edit Mode.

It is disabled by default and can be activated by clicking on its checkbox. A click on OK closes the properties window and returns to the command prompt window. It is from that moment on possible to select items on the screen by left-clicking, just like it is done in any word processor. Items can be copied with the keyboard shortcut Ctrl-C.

Have a different way of copying and pasting from the Windows command prompt? Let me know in the comments.

Let’s take a look and see how this is done.

Before we start…

There is always a “before” right? In this case I wanted to touch base with everyone to make sure it is know how you can work with the bash history. There is one way the bash history is immediately useful to the user. The bash history makes it easy for recalling the last commands run. If you open up a terminal window and start hitting the up arrow on your keyboard you can run through all of the commands contained in your bash history.

So all you need to do is keep hitting the up arrow until you see the command you wanted to run. This will save you time by keeping you from having to type long commands over and over. It can also help you troubleshoot by showing you what commands you have recently run, which will allow you to deduce what has happened to your machine.

How to delete the history

There are two steps to deleting your bash history. The first step is to delete the ~/.bash_history file. This won’t work completely because there will still be a history stored in RAM. So, to get rid of THAT history you have to run the command history -c. Once that command is issued, your bash history will be completely clear.

Not keeping your history

What if, for whatever reason, you do not want your bash history to be retained at all? You can do this. You can do this for either all users or specific users. To turn off bash history for all users you would need to issue the command:

echo "unset HISTFILE" >> /etc/profile

To turn off bash history for a single user issue the command:

echo "unset HISTFILE" >> /home/USER/.bash_profile

Where USER is the user you want bash history turned off.

Once you’ve done either of the above, bash history will be turned off for good.

History size

Remember, you can control the size of your bash history by editing the lines in your ~/.bashrc file:

HISTSIZE=1000

Change the entry to match the amount of commands you want to retain in your history.

Final thoughts

Bash is an amazing and powerful tool for any and all Linux users. Although you do not have to ever touch the command line, in modern Linux desktops, you may someday have to use the command for either a server or remote access to another desktop. For whatever the reason, you will want to either take advantage of the bash history.

So…let’s take a look at some nifty trickery with the Linux command line.

seq

This is one of the coolest (and most useful) tips I have ever come across.  The seq command will print out a sequence of numbers. So if you issue the command:

seq 0 50

You will see the numbers 0-50 printed out on the terminal. Very simple. Sure that’s great but what good is a sequence of numbers? Let’s apply it and find out. Remember you can always declare a value in bash and by making use of the $ symbol you can use variables in your commands. So what happens if you issue the command:

for k in `seq -w 1 50` ; do ssh 192.168.100.$k uptime ; done

What happens is ssh will walk through all the addresses from 192.168.100.1 to 192.168.100.50 until it finds one with an ssh server accepting connections. When it does it will ask you for the users password and then print out the uptime of that machine. Very handy indeed.

How much space left?

Quick, how much space do you have left on your drive(s)?  And where are those drives mounted on? Do you have the answer yet? If you had a terminal window open you could have issued the command df -h and you would have seen, in a user-friendly format, the percentage of your hard disk space that has been used. Very handy command.

Those pesky bash colors

Do you prefer the colors you see in bash? Do you even know about the colors in bash? From the command line issue the command ls you will see that files are black, folders are blue, executables are green (that’s a simplistic explanation). What if those colors bother you (or cause your pretty transparent terminal from giving you a good read on your file listing)? You can turn that off easily from the command by issuing:

ls --color=none

Of course that is a one-time deal. In order to make this permanent you have to edit your ~/.bashrc file. In that file you will see the following entry:

alias ls='ls --color=auto'

Comment out that entry and ls will no longer use color.

Find files modified TODAY

If you have saved a file today and you can’t remember where you saved it, you can use the find command to print out all files modified today. The command:

find ~ -type f -mtime 0

Will print out a listing of all files that were modified on the day the command was issued (today).

Install from source to package

That might not make any sense. It will in a moment. Say you’ve downloaded the source for a package that you want to install, but you want to keep with the standard for your distribution by installing it from a package (so your package manager is aware of it). You can do this with the help of the checkinstall application. This isn’t installed by default, but you can install it with the command sudo apt-get install checkinstall. Once installed you can install from source with the command (from within the source code directory):

./configure && make && checkinstall

This will ask you some questions regarding your distribution and will install the application.

I have found, outside of using an application’s built-in spell checking, two particular tools that I prefer. These tools are GoldenDict and Dict. The former is a splendid GUI tool, whereas the latter is a lightning-quick command line tool. Let’s see which of these tools suits your needs best.

GoldenDict

GoldenDict is a feature-rich graphical dictionary program that allows the user to take advantage of multiple local dictionaries as well various on-line dictionaries. It’s easy to use and actually works in conjunction with other applications.

To install GoldenDict just do the following:

1. Open up your Add/Remove Software Utility.
2. Search for “goldendict” (No quotes).
3. Mark GoldenDict for installation.
4. Click Apply to install.

Figure 1

Once installed, you will find GoldenDict in the Applications > Office menu.

When you fire up GoldenDict you will the main window where you can take care of all of your lookups (see Figure 1). The usage is fairly straight-forward. You enter your word in the “Look up” text area and hit Enter. The results will appear as the disambiguation in the left pane and the actual definition in the right pane.

Now…let’s say you want to extend GoldenDict out to your other applications. If you click on Edit > Preferences and then click on the Scan Popup tab you can enable GoldenDict to work on any text you highlight in any application. I will warn you…this can get in the way of every day use. To that end I always enable this feature but enable it along with the “Only show popup when all selected keys are kept pressed”. With this feature you can configure a key (either Alt, Ctrl, Shift, or Meta) that must be pressed along with the word selection. When this combination is done a popup will appear definining the word.

Dict

Now let’s take a look at a much simpler tool – dict. Dict is a command line only tool that allows you to search online dictionaries (or local dictionaries if you have them installed) for word definitions. Installing dict is simple:

1. Open up a terminal window.
2. Issue the command sudo apt-get install dict (or a suitable command for your distribution).
3. Accept the dependencies.
4. Wait until the installation is complete.

When you have dict installed, the usage is simple:

dict -h SERVER WORD

Where SERVER is the server you want to use and WORD is the word you want to look up. Normally you could just issue dict WORD but currently the default servers for dict are all not responding. So in order to get around that you need to define a server to use. One server that is working is dict.tu-chemnitz.de. To use this server you would issue the command:

dict -h dict.tu-chemnitz.de WORD

Where WORD is the word you want to look up. You would then be rewarded with the definition of the word in question.

But what if you are a serious power user who wants multiple terminal windows open, but doesn’t want to deal with tabs? Is there a tool for you? Why yes there is. That tool is Terminator. Terminator is a multi-view terminal window that will have you doing console backflips and other impressive feats of administrative kung-fu. Let’s take a look at this magic tool.

Installation

As usual, the installation of Terminator is as simple as the following:

1. Open up a terminal window.
2. Issue the command sudo apt-get install terminator.
3. Type your sudo password and hit Enter.
4. Accept any dependencies that are necessary.
5. Close out the terminal when the installation is complete.

You are now ready to be wow’d via terminal.

General usage

Figure 1

Starting Terminator is simple. You can either click Applications > Accessories > Terminator or you can click Alt+F2 and then enter terminator in the run dialog. When you do start up terminator you will see what looks like a standard terminal window. It’s not until you start really playing around with this tool that you discover what it can do.

When Terminator is open you can use the following key combinations:

• Ctrl-Shift-E: To split the view vertically.
• Ctrl-Shift-O: To split the view horizontally.
• Ctrl-Shift-P: For focus to be active on the previous view.
• Ctrl-Shift-N: For focus to be active on the next view.
• Ctrl-Shift-W: To close the focused view.
• Ctrl-Shift-Q: To exit terminator.
• F11: Fullscreen.

A view can be thought of as a pane. Figure 1 shows Terminator open with four views. To get this I would focus on the original, single pane and hit the combination Ctrl-Shift-E which would split the pane into two vertical panes. Now, with the focus on the left pane click Ctrl-Shift-O and it will split the left pane into two horizontal panes. Finally, with the focus on the right vertical pane, click Ctrl-Shift-O to split the right pane into two horizontal panes. You should now have four smaller panes which to use.

NOTE: You can also start Terminator borderless from the command line using the -b switch like so:

terminator -b

Groups

You can also create groups and then apply each pane to one of those groups. This makes keeping Terminator organized much easier. To do this click on the upper left corner of one of the panes and then select New Group from the drop-down. Give the group a name and then, once you have all of your groups created, you can associated each pane to a particular group. You can also remove groups from the same dropdown menu. NOTE: When you close terminator you lose all of your groups.

Final thoughts

If you are a terminal power user you will certainly appreciate the power Terminator offers. Give this a try and see if your ADHD is made happy with this handy tool.

Although you won’t find all of the standard features found in most modern file managers, you will find emelFM2 has a few tricks of its own that make it worth (at least) giving a try. And, of course, any old school user will be happy to have this file manager sitting alongside the standard Nautilus, Dolphin, or Thunar.

In this Ghacks article I will show you how to install and make use of the emelFM2 file manager.

Installation

Since emelFM2 is a GTK+ toolkit it’s fairly universal on X11 systems. I found emelFM2 in both the standard repositories for Ubuntu 10.04 and Fedora 13. So installation can be as simple as:

1. Open up your Add/Remove Software tool.
2. Search for “emelfm2″ (no quotes).
3. Mark emelFM2 for installation.
4. Click Apply to install.

Once installed, you will find emelFM2 in Start > System Tools > emelFM2.

Usage

Figure 1

When you start up emelFM2 the window that greets you will look very familiar (see Figure 1). If you’ve ever used Midnight Commander or even an FTP application like gFTP, you will be immediately at home with emelFM2.

Let’s say you want to move a file (or directory) from one location to another. To do so you would navigate on the left pane to the source, select the file (or folder), navigate on the right to the target, and then click the Move button in the middle of the panes.

Or say you want to just open a file. To do this you would navigate to the location of the file on either the left or right pane, and double click the file to open it. You could also right-click the file and select from any number of actions (such as change ownership, change permissions, copy, link, link-as, delete, and more).

Other features

Naturally, a tool like this would need some other features to make it attractive. And emelFM2 doesn’t disappoint. One of the nice handier features of emelFM2 is the built-in command line tool. at the bottom of the window you will see a small text area (see Figure 1). This text area allows you to enter commands that will be enacted upon the selected file.

You can also calculate disk usage of items. You might be asking yourself why this would be useful, since the file size is already displayed in the main panes. The disk usage tool allows you to calculate the exact file size of either a single file or multiple files. With this you can select multiple files and the click the disk usage button (bottom section of the window, eighth icon from the right) to give you the total amount used by the selected files.

emelFM2 also allows you to mount/unmount devices. To unmount a device you would select the device in either pane and then click the unmount icon (fourth button from the right near the bottom of the window). To mount a device you use the same process.

emelFM2 also has an interesting take on the filtering task. If you click the Filter icon (top right, third from the right for the right pane, top left, third from the left for the left pane) a drop-down will appear allowing you to select from:

• Name Filter
• Size Filter
• Date Filter
• Directories too

When you select any of he top three a new window will open allowing you to create a specific filter. For example, if you want to filter only files modified since a specific date, you would do the following:

Select the Date Filter

In the resulting window select “modified since” from the drop-down.

Enter the date you want to specify.

Click OK.

Figure 2

As soon as you click OK the directory will be refreshed to show only the results that match your filter. You will know when a directory is being filtered because the filter icon will have a line slashed through it (see Figure 2).

Final thoughts

Although many users might find emelFM2 a bit out-dated, anyone that was weened on the likes of Midnight Commander will find themselves right at home with this fast, light file manager. And with a few extra features rolled in, emelFM2 is an attractive alternative to the usual fare.

The forfiles command can be coupled with processing options to delete those files, or create a list of all files that match the filters. Lets take a closer look at the forfiles command.

FORFILES [/P pathname] [/M searchmask] [/S]
[/C command] [/D [+ | -] {dd/MM/yyyy | dd}]

Description:
Selects a file (or set of files) and executes a
command on that file. This is helpful for batch jobs.

Parameter List:
/P pathname Indicates the path to start searching.
The default folder is the current working
directory (.).

/M searchmask Searches files according to a searchmask.
The default searchmask is ‘*’ .

/S Instructs forfiles to recurse into
subdirectories. Like “DIR /S”.

/C command Indicates the command to execute for each file.
Command strings should be wrapped in double
quotes.

The default command is “cmd /c echo @file”.

The following variables can be used in the
command string:
@file – returns the name of the file.
@fname – returns the file name without
extension.
@ext – returns only the extension of the
file.
@path – returns the full path of the file.
@relpath – returns the relative path of the
file.
@isdir – returns “TRUE” if a file type is
a directory, and “FALSE” for files.
@fsize – returns the size of the file in
bytes.
@fdate – returns the last modified date of the
file.
@ftime – returns the last modified time of the
file.

To include special characters in the command
line, use the hexadecimal code for the character
in 0xHH format (ex. 0×09 for tab). Internal
CMD.exe commands should be preceded with
“cmd /c”.

/D date Selects files with a last modified date greater
than or equal to (+), or less than or equal to
(-), the specified date using the
“dd/MM/yyyy” format; or selects files with a
last modified date greater than or equal to (+)
the current date plus “dd” days, or less than or
equal to (-) the current date minus “dd” days. A
valid “dd” number of days can be any number in
the range of 0 – 32768.
“+” is taken as default sign if not specified.

/? Displays this help message.

This help file can be opened by entering the command forfiles /? in a command prompt. Press Windows-R, type cmd, and hit enter to launch the command line in Windows.

The command

forfiles /P c:\test\ /M .doc /S /D -10

searches the directory c:\test and all its subdirectories for files with the .doc extension that are older than 10 days.

The parameter /p followed by a directory defines the starting directory, /s includes subdirectories in the search, /m filters the files and folders based on the entered string, and /D defines the date or a time span.

The /C command is used to process the files that are found further. It can for instance be used to

/C "cmd /c echo @fname" > test.txt

echo the names of each file found and save the results in text.txt in the same directory.

The full command then looks like this

forfiles /P c:\test\ /M .doc /S /D -10 /C "cmd /c echo @fname" > test.txt

Another possibility is to delete the files that match the search, this is done with the command

/C "cmd /c del @File

It is however recommended to test the output first, before issuing the delete command to make sure that only the right files are deleted.

Experienced users may create a batch file to execute forfiles regularly.

In this article I will walk you through the creation of new profiles and show you why you might want them.

Assumptions

First and foremost, this article assumes you actually use the terminal and assumes you use it a lot. The pedestrian user of the terminal might not see a need for multiple profiles for a terminal window. But if you use the terminal a lot, and for various reasons, you might see how multiple profiles can make a difference.

Creating new profiles

Figure 1

Let us first take a look at how profiles are created. To create (or edit) a profile click Edit > Profiles. This will bring up a new window (see Figure 1) where you can add, edit, or delete profiles at will.

As you can see, in Figure 1, I have two current profiles – default and “no trans”. My default profile fits in with my current desktop scheme (RGBA, with heavy transparency). There are times when I need to more closely evaluate text (such as when viewing top or combing through a configuration file. For those times I switch to the “no trans” profile which is a non-transparent profile I created.

To create a new profile click the New button. When you do this a small window will open where you give your new profile a name and choose which of your current profiles to base the new profile on. Let’s say, for the sake of example, I want to create a profile for any time I am using the terminal as the root user. This can come in very handy (and keep you from doing something you don’t want to do).  For this I am going to call the profile “Root” and base it on “no trans”. Once you’ve done that the main profile editor window will appear (see Figure 2) .

In this new window you can change quite a bit for your profile. For a profile to work as the administrative user you might want to do something like create a white background with red text, or a red background with black text. For such an instance I like to alter the Title and command to ensure there is no mistaking I am using the administrative user. To do this click on the Title and Command tab and then change the Initial title to be something like ROOT User: USE CAUTION. You can then select to prepend this title if the terminal command sends it’s own title (which is often the case).

Figure 3

The new “root” profile will look something like that in Figure 3.

Switching profiles

This is simple, and can be done on the fly. All you need to do is click Terminal > Change Profile and select the profile you want.

Final thoughts

Make use of the gnome-terminal profiles and your life will be much easier. There are a lot of reasons why you would want to use them and tons of modifications you can make to them.

It is not possible to uninstall software in Safe Mode if the service is not running, that is highly problematic if a software is responsible for PC issues.

There is however an option to start the Windows Installer Service in Safe Mode, so that software can be uninstalled afterwards.

windows installer service error

The Windows Installer Service can’t be started immediately, it is necessary to patch the Registry first.

Open the Windows Registry Editor with the keyboard combination Windows-R, type regedit and hit enter. It can also be launched by clicking on the start orb, and entering regedit in the run box in the Start Menu followed by enter.

Locate the following Registry key

HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\

Right-click on Minimal and select New > Key. Name the key MSIService and change the default value to Service by double-clicking it.

windows safe mode

This makes the Windows Installer Service available in minimal Safe Mode. You may want to repeat the steps for the networking Safe Mode as well. All steps are the same, except for the starting Registry key.

HKLM\SYSTEM#92;CurrentControlSet\Control\SafeBoot\Network\

The Windows Installer Service needs to be started afterwards, this can be done by clicking on the start orb again, entering services.msc and hitting enter.

Locate Windows Installer in the services listing, right-click it and select start. Alternatively execute the following command via the command line:

net start msiserver

It is furthermore possible to issue all commands via the command line. To enable Windows Installer in minimal Safe Mode execute the following command:

REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\MSIServer" /VE /T REG_SZ /F /D "Service"


For Safe Mode with network:

REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\MSIServer" /VE /T REG_SZ /F /D "Service"


The freeware SafeMSI offers to automate the Registry editing and service starting. Just double-click the program in Safe Mode to enable Windows Installer.

One of those ways is with the help of bash aliases. A bash alias is a way to create shortcuts to commands that would normally take a lot of typing or are a challenge to remember. So instead of ssh -v -l jlwallen 192.168.1.10 I could enter just desktop or whatever I want that shortcut to be. In that vein, I am going to offer up some very handy shortcuts for you to add to make your command line usage more efficient.

Where they go

If you open up a terminal and issue the command ls -a |less you should come across a file called ~/.bashrc. This file is very powerful and handles a LOT of tasks. One such task is that of aliases. Within that file you will find the section:

# Alias definintions

This is where you put your user-created aliases…and where we will place the aliases listed below. Once you create the aliases, you will notice they don’t work within the same terminal you used to add them with your text editor. You have to fire up a new terminal to make sure they work. Because of this, always leave your original terminal open to make sure the new terminal will still work. I have witnessed a user fubar their bash such that the terminal would no longer open. So use caution when randomly closing your terminals. Now, on the aliases.

Ask before you remove

Admit it, you’ve accidentally deleted a file that could have been prevented if you had used the -i switch with the rm command. To avoid this common mistake, let’s add an alias such that any time the rm command is issued, it is done with the -i switch. This alias would look like:

alias rm=”rm -i”

Secure shell

As I mentioned earlier, secure shell’ing to a machine can be a real pain when you do it over and over. Create an alias like so:

alias server1=”ssh -v -l USER ADDRESS”

Where USER is the user name you would log in with and ADDRESS is the address of the machine you are remoting into.

Bookmark alias

Here’s a fun one. You can open up your browser to a specific bookmark, from the command line with an alias like so:

alias ghacks=”chromium-browser http://www.ghacks.net”

Of course you would replace chromium-browser with your default browser and the URL with the address you want the browser to open up to.

RPM batch installation

Say you do a lot of batch installations of RPMS. And say you always save your RPM files to ~/RPMS. You can add an alias to quickly install those RPMS like so:

alias brpm=”rpm -ivh ~/RPMS/*rpm”

Update/upgrade with apt

Instead of having to issue both command for updating apt and upgrading your installation, combine them into one easy to use alias like so:

alias update=”sudo apt-get update ; sudo apt-get upgrade”

You will have to enter your sudo password once and the update/upgrade will take place.

Final thoughts

Bash aliases are only limited to your imagination. After you spend enough time with the command line you will see that these aliases can really make your day to day Linux life much easier.

Why?

Why continue to break out more command line tips? Simple. Although it is very possible to get through the day (maybe even your entire Linux lifetime) without dropping to the command line, there are times when the command line is the best tool for the job. And knowing the command line in Linux is knowing power. So…let’s put some power at our fingertips.

Uptime

I had a friend once that had a Linux box with an uptime of over three years. THREE YEARS! The box finally came down because a NIC went bad and he had to shut it down to replace it. It broke his heart. Every day he would send me his uptime and we would both “oooh and ahhh” over it. How did he do this? The uptime command. This command does one thing and it does it well – it tells you how long your machine has been running. You issue this command like so:

uptime

When you issue the command you will see something like:

06:57:40 up 3 days, 22:15,  2 users,  load average: 0.93, 0.66, 0.49

(My uptime is lame right now. We had a nasty thunderstorm and I had to shut down my machines).

Some people, like myself, add their uptime to their email signatures. You can see how to do this in my article “Add uptime and/or fortunes to your email signature“.

less is more

One command line issue that might bug you is when you issue a command like dmesg and the output flashes by so quickly you can’t read it. There is a very simple way around this. If you pipe the output of the dmesg command to the less command you can read the output “one page at a time”. To do this you would issue the command like so:

dmesg | less

Or you use more to do the same thing (almost) like:

dmesg | more

The difference? With less you can scroll backwards. With more you can not.

Save that output

But what if you want to save your output of a command like dmesg so you look at it earlier or even email it to someone to look through? You can take multiple screenshots of each less page from dmesg…or…you can direct the output to a file. This is done like so:

dmesg > FILE_NAME

Where FILE_NAME is the name of the file that will hold the output. NOTE: If you will be sending that output to a windows user you might want to include the .txt extension for easy opening.

Final thoughts

Sometimes those “old school” tips can really save your hide. Just because they are “old school” doesn’t mean they don’t have their uses. In fact, I make use of less and output re-direction every day. Once you start using them, you will find yourself using them more and more.

Guake is a drop-down terminal that fits all of these needs perfectly. It’s for the GNOME environment and is easy to use and is one of those tools that, once you start using, you’ll wonder why you hadn’t been using all along. In this article I will show you how to install and use the Guake drop-down terminal so your Linux command line can be as finger-tip ready as possible.

Installation

Fortunately the installation of Guake is simple. Because it lives in the standard repositories of all of the major distributions, you can install Guake with a command like this:

yum install guake

or

sudo apt-get install guake

Figure 1

If you use the former command you will have to do so after you su to the root user. Once installed you will need to start Guake. You do so by clicking Applications > Acesssories > Guake Terminal. Once started Guake will reside in your notification area as an icon (see Figure 1). The icon is the Green downward pointing arrow. If you right-click that icon can access the Guake preferences.

Configuration

There isn’t too much to configure with Guake. From the preferences window you can take care of such items as:

• The default shell: You will most likely want to stick with the default here.
• Main window height: How tall do you want Guake when it is opened?
• Appearance: Text color/font, background color/transparency/image.
• Various keyboard shortcuts

By default Guake is not set to start up on login. One of the surprises that always catches me with Guake is you can not set this through the properties window. Instead you will have to set this through the GNOME Start up Applications tool. Access this by clicking System > Preferences > Startup Applications. When this window is open scroll down until you find the Guake entry, click the Guake checkbox, and click Close. Now Guake will start up when you log in.

Usage

Figure 3

To use Guake you simply click the keyboard shortcut configured in the Preferences window. By default that key is F12.  When you click the Open key Guake will drop down for you to use. Figure 3 shows Guake in action, running the top command. By default Guake will remain above all other windows until you dismiss it (by clicking the same key you did to open it).

You can use Guake as you would a normal terminal window. And, like most good modern terminals, you can have multiple tabs open. To open a new tab in Guake, by default, you higt <Ctrl><Shift>t.

If you want to know other handy keyboard shortcuts, go back to the Preferences window and look at the Keyboard shortcuts tab.

Final thoughts

If you frequently use the command line, you will very much be glad you have found Guake. With a terminal window so accessible, your work will be that much more efficient. And we all know efficiency is a key factor in every day computing (at least for many of us).

Installation?

Fortunately your distribution should come with the netstat command pre-installed. To check this, open up a terminal window (that’s where you will use netstat anyway) and issue the command which netsat. This command should return something like /bin/netstat. That will tell you that the tool is installed and where the executable is.

Usage

Because netstat offers such a variety of options, it might be best if I first list some of the more useful options.

a: Shows the state of all sockets and routing table entries.

c: Display information continuously.

d: Show the state of all interfaces that use DHCP.

e: Show extended information.

g: Show the multicast group membership information for both IPv4 and IPv6.

i: Display a table of all network inferfaces.

l: Limit statistics to a defined interface.

M: Show multicast routing tables.

n: Shows network addresses as numbers instead of the default symbols.

p: Show address resolution tables.

P: Limit statistics to a defined protocol.

r: Show all routing tables.

t: Show TCP connections.

u: Show UDP connections.

v: Use verbose mode for output.

So let’s take a look and see how these can be used together.

netstat

By itself (no options) this command prints out generic statistics of the host you are currently connected to.

netstat -an

This command will display all connections to the host, including source and destination addresses and ports, and displays them as numbers.

netstat -rn

This command will display the routing table for the host in numeric form.

netstat -r

This command will display your routing table for your host.

netstat -natp

This command will display active TCP connections in numerical form.

netstat -t –listening

This will show you all tcp ports you host is listening on.

Figure 1

netstat –statistics

This command will display various statistics for your host’s interfaces. Note that this command will display a LOT of statistics. A snippet of the output will look like that shown in Figure 1.

As you can see, this command will display quite a bit of information. On top of that you might need to pipe this command through the less command in order to see it more easily. That full command would look like netstat –statistics | less. Using it that way would allow you to use your arrow keys to scroll up and down through the ouput.

Final thoughts

Although not an exhaustive look at the netstat command, this will get you started and using this handy tool. Since there are so many switches and options to use with netstat, in order to cover them all, take a look at the netstat man page (issue the command man netstat) where you can see each and every switch explained.



Tab completion

This tip is for the novice. There are a lot of commands on the Linux operating system (in my /usr/bin directory there is 1736 commands). Hard to remember all of them. Or sometimes a command will have a number of variations (like in the case of beagle) And sometimes, it’s just tiring typing all of those commands. Fortunately the Tab key is there to help you out. Open up your terminal window and do the following:

1. Type beagle
2. Hit the Tab key twice

You should see a complete listing of all commands that start with beagle. Say you want to run beagle-index-info. You can do this by typing beagle-ind and then hitting the Tab key one time.

Run second command with first commands arguments

Say you need to find out what the directory /home/jlwallen/.e16/themes contains, but when you run the command ls /home/jlwallen/.e16/themes you see that the directory doesn’t exist. Looks like you will have to create that directory. Normally you would do this by typing mkdir /home/jlwallen/.e16/themes (or mkdir ~/.e16/themes). You can use a neat little trick to take the arguments from the previous command and add them to a new command like so:

mkdir !*

The above command would be the equivalent of (in our example above) mkdir /home/jlwallen/.e16/themes).

Search your bash history

If you can’t remember how you ran a specific command, you can use your bash history to help you. If you hit <Ctrl>r you will be in a special bash search prompt that looks like:

(reverse-i-search)`':

From this prompt you can enter a portion of the command and immediately see a command that contains what you type. If the command is the one you are looking for, hit the Enter key to execute that command.

Another method of searching bash history

This one is simple. If you can’t remember the last few commands you entered, just hit the up arrow on your keyboard to look through the list. When you find the command you want to run, hit Enter.

Create recursive directories with one command

Have you ever had to create entire directory trees and did so like:

mkdir ~/test

mkdir ~/test/test1

mkdir ~/test/test1/test2

mkdir ~/test/test1/test2/test3

You create all of these subdirectories with a single command:

mkdir -p ~/test/test1/test2/test3

Run a second command only if first command succeeds

You can string two commands together in such a way that the second of the two commands will work if (and only if) the first command succeeds. Let’s say you are going to use the wget command to download a tar file and then you want to immediately unpack that file. You could do so with this:

wget http://ADDRESS_OF_SERVER/filename.tgz && tar xvzf filename.tgz

The above would unpack filename.tgz if (and only if) it is successfully downloaded.

Final thoughts

That should get you going for a bit. I’ll revisit this topic in the future so you can keep your command-fu skills sharp. And, by all means, if you have a cool command-line tip you want to share, please do so.