15 Linux Terminal Commands That Will Rock Your World

The Linux command line offers a much easier, and cross-distribution, method of completing common tasks.

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Useful Command Line Keyboard Shortcuts

The following keyboard shortcuts are useful and will save you time:

CTRL+U: Cuts text up until the cursor.
CTRL+K: Cuts text from the cursor until the end of the line.
CTRL+Y: Pastes text.
CTRL+E: Moves the cursor to the end of the line.
CTRL+A: Moves the cursor to the beginning of the line.
ALT+F: Jumps forward to the next space.
ALT+B: Skips back to the previous space.
ALT+Backspace: Deletes the previous word.
CTRL+W: Cuts the word behind the cursor.
Shift+Insert: Pastes text into a terminal.

So that the commands above make sense, look at the next line of text.

sudo apt-get intall programname

There's a spelling error in the command, and for the command to work, intall needs to be changed to install.

Imagine the cursor is at the end of the line. There are several ways to get back to the word install to change it.

You could press ALT+B twice, which would put the cursor in the following position (denoted by the ^ symbol):

sudo apt-get^install programname

Then, press the cursor key and insert the s into install.

Another useful command is Shift+Insert, especially if you need to copy text from a browser into the terminal.

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SUDO !!

You'll appreciate this command every time you enter a command, and the words Permission denied appear.

How do you use sudo !!? Imagine you entered the following command:

apt-get install ranger

The words Permission denied appear unless you are logged in with elevated privileges.

sudo !! runs the previous command as sudo. So the previous command now becomes:

sudo apt-get install ranger

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Pause Commands and Run Commands in the Background

Pause terminal applications linux commands screenshot

To run terminal commands in the background, press:

CTRL+Z: Pauses an application
fg: Returns you to the application

Imagine you have opened a file in nano as follows:

sudo nano abc.txt

Halfway through typing text into the file, you realize that you want to type another command into the terminal, but you can't because you opened nano in foreground mode.

When you press CTRL+Z, the foreground application pauses, and you are returned to the command line. You can then run any command you like, and when you finish, return to your previously paused session by entering fg into the terminal window and pressing Enter.

An interesting thing to try is to open a file in nano, enter some text, and pause the session. Then, open another file in nano, enter some text, and pause the session. If you enter fg, you return to the second file you opened in nano. If you exit nano and enter fg again, you return to the first file you opened in nano.

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Use nohup to Run Commands After You Log Out of an SSH Session

The nohup command is useful if you use the ssh command to log in to other machines. Use it to log in to another computer remotely using ssh and run a command that takes a long time, then exit the ssh session but leave the command running.

For example, you can use a Raspberry PI to download distributions for review purposes. Connect to the Raspberry PI via ssh from a laptop. If you started downloading a large file on the Raspberry PI without using the nohup command, then you must wait for the download to finish before logging off the ssh session and before shutting down the laptop. If you did this, then you may as well have not used the Raspberry PI to download the file at all.

To use nohup, all you have to type is nohup followed by the command as follows:

nohup wget 
http://mirror.is.co.za/mirrors/linuxmint.com/iso//stable/17.1/linuxmint-17.1-cinnamon-64bit.iso &

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Run a Linux Command 'at' a Specific Time

Schedule tasks with at command through Linux terminal

The nohup command is good if you are connected to an ssh server, and you want the command to remain running after logging out of the ssh session.

Imagine you want to run that same command at a specific point in time.

The at command allows you to do just that. at can be used as follows.

at 10:38 PM Fri
at> cowsay 'hello'
at> CTRL+D

The above command runs the program cowsay at 10:38 p.m. on Friday evening.

The syntax is at followed by the date and time to run.

When the at> prompt appears, enter the command you want to run at the specified time.

The CTRL+D keyboard shortcut returns you to the cursor.

There are many date and time formats, and it's worth checking the man pages for more ways to use at.

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Man Pages

Man pages offer an outline of what commands do and the switches that can be used with each command.

The man pages are kind of dull on their own. You can, however, do things to make your usage of man more appealing.

export PAGER=most

You will need to install most for this to work, but when you do, it makes your man pages more colorful.

You can limit the width of the man page to a certain number of columns using the following command:

export MANWIDTH=80

If you have a browser available, you can open any man page in the default browser by using the -H switch as follows:

man -H <command>

Note this only works if you have a default browser set up within the $BROWSER environment variable.

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Use htop to View and Manage Processes

Which command do you currently use to find out which processes are running on your computer? If you use ps and you use various switches to get the output you desire, install htop.

htop provides a list of all running processes in the terminal, much like the file manager in Windows.

You can use a mixture of function keys to change the sort order and the columns that are displayed. You can also kill processes from within htop.

To run htop, type the following into the terminal window:

htop

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Navigate the File System Using ranger

If htop is useful for controlling the processes running via the command line, then ranger is useful for navigating the file system using the command line.

You will probably need to install ranger to be able to use it, but once installed, you can run it by typing the following into the terminal:

ranger

The command line window will be much like any other file manager, but it works left to right rather than top to bottom. When you use the left arrow key, you work your way up the folder structure, and the right arrow key works down the folder structure.

It is worth reading the man pages before using ranger so that you can get used to the available keyboard switches.

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Cancel a Shutdown

Abort a scheduled shutdown with the command:

shutdown -c

If the shutdown has started, then it may be too late to stop the shutdown.

Another command to try is as follows:

pkill shutdown

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Kill Hung Processes the Easy Way

Imagine you are running an application, and for whatever reason, it hangs. You could increase the process's priority with nice, but it's often better not to give a runaway process more resources.

You could use ps -ef to find the process and then kill the process, or you could use htop.

There is a quicker and easier command called xkill.

Type the following into a terminal, then click the window of the application you want to kill.

xkill

What happens though if the whole system is hanging?

Press the Alt+SysRq keys on your keyboard and while the keys are held down, type the following letters slowly:

REISUB

This technique restarts your computer without using the power button.

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Download Youtube Videos

Generally speaking, many people are happy for YouTube to host the videos and for them to watch videos by streaming them through a media player.

If you know you are going to be offline for a while, then you may wish to download a few videos onto a pen drive and watch them at your leisure. All you have to do is install youtube-dl from your package manager.

Use youtube-dl as follows:

youtube-dl url-to-video

Get the URL to any video on Youtube by clicking the share link on the video's page. Copy the link and paste it into the command line (using the Shift+Insert shortcut).

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Download Files From the Web With wget

The wget command downloads files from the web using the terminal.

The syntax is as follows:

wget path/to/filename

For example:

wget http://sourceforge.net/projects/antix-linux/files/Final/MX-krete/antiX-15-V_386-full.iso/download

There are a large number of switches that can be used with wget such as -O, which lets you output the filename to a new name.

In the example above, AntiX Linux is downloaded from Sourceforge. The filename antiX-15-V_386-full.iso is long. It would be nice to download it as antix15.iso. To do this, use the following command:

wget -O antix.iso http://sourceforge.net/projects/antix-linux/files/Final/MX-krete/antiX-15-V_386-full.iso/download

Downloading a single file doesn't seem worth it; you could easily navigate to the web page using a browser and click the link.

If, however, you want to download a dozen files, then being able to add the links to an import file and use wget to download the files from those links is quicker.

Use the -i switch as follows: