Book Image

Learn Linux Quickly

By : Ahmed AlKabary
Book Image

Learn Linux Quickly

By: Ahmed AlKabary

Overview of this book

Linux is one of the most sought-after skills in the IT industry, with jobs involving Linux being increasingly in demand. Linux is by far the most popular operating system deployed in both public and private clouds; it is the processing power behind the majority of IoT and embedded devices. Do you use a mobile device that runs on Android? Even Android is a Linux distribution. This Linux book is a practical guide that lets you explore the power of the Linux command-line interface. Starting with the history of Linux, you'll quickly progress to the Linux filesystem hierarchy and learn a variety of basic Linux commands. You'll then understand how to make use of the extensive Linux documentation and help tools. The book shows you how to manage users and groups and takes you through the process of installing and managing software on Linux systems. As you advance, you'll discover how you can interact with Linux processes and troubleshoot network problems before learning the art of writing bash scripts and automating administrative tasks with Cron jobs. In addition to this, you'll get to create your own Linux commands and analyze various disk management techniques. By the end of this book, you'll have gained the Linux skills required to become an efficient Linux system administrator and be able to manage and work productively on Linux systems.
Table of Contents (24 chapters)

Showing unique lines

You can use the uniq command to omit repeated lines in a file. For example, notice that the line Cherries are red. is included four times in the file facts.txt:

To view facts.txt without repeated lines, you can run:

elliot@ubuntu-linux:~$ uniq facts.txt 
Apples are red.
Grapes are green.
Bananas are yellow.
Cherries are red.
Sky is high.
Earth is round.
Linux is awesome!
Cherries are red.
Grass is green.
Swimming is a sport.

Notice that Cherries are red. is still shown twice in the output. That’s because the uniq command only omits repeated lines but not duplicates! If you want to omit duplicates, you have to sort the file first and then use a pipe to apply the uniq command on the sorted output:

elliot@ubuntu-linux:~$ sort facts.txt | uniq 
Apples are red.
Bananas are yellow.
Cherries are red.
Earth is round.
Grapes are green.
Grass is green.
Linux is awesome!
Sky is high.
Swimming is a sport.

Boom! We have successfully omitted repeated and duplicate lines.