bash Archives

Bash regexps for beginners with examples

11 August 2020 by Roel Van de Paar

Using regular expressions in Bash provides you with plenty of power to parse nearly every conceivable text string (or even full documents), and transform them into nearly any output desirable. If you regularly use Bash, or if you regularly work with lists, textual strings, or documents in Linux, you will find that many jobs can be simplified by learning how to use regular expressions in Bash. Continue reading to learn basic Bash regular expression skills! If you are already familiar with basic regular expressions in Bash or another coding language, see our more advanced bash regular expressions. If not, continue reading to learn basic Bash regular expression skills!

In this tutorial you will learn:

How to use regular expressions on the command line in Bash
How regular expressions can parse and transform any text string and/or document
Basic usage examples of regular expressions in Bash

How to count number of columns in CSV file using bash shell

7 August 2020 by Admin

Probably the easiest way to count number of columns in CSV file using bash shell is simply count number of commas in a single row. In the following example the content of the file myfile.csv is:

$ cat myfile.csv 
1,2,3,4,5
a,b,c,d,e
a,b,c,d,e

Commands on how to delete a first line from a text file using bash shell

7 August 2020 by Lubos Rendek

In this short config we will show a multiple options on how to remove a first line from a text file. Here is the content of our sample file.txt.

$ cat file.txt 
line1
line2
line3
line4

Multi-threaded Bash scripting & process management at the command line

1 July 2020 by Roel Van de Paar

The things you can do using Bash script are limitless. Once you begin to developed advanced scripts, you’ll soon find you will start to run into operating system limits. For example, does your computer have 2 CPU threads or more (many modern machines have 8-32 threads)? If so, then you will likely benefit from multi-threaded Bash scripting and coding. Continue reading and find out why!

In this tutorial you will learn:

How to implement multi-threaded Bash one-liners directly from the command line
Why multi-threaded coding almost always can and will increase the performance of your scripts
How background and foreground processes work and how to manipulate job queues

Bash Loops with examples

16 June 2020 by Roel Van de Paar

Ready to dive into Bash looping? With the popularity of Linux as a free operating system, and armed with the power of the Bash command line interface, one can go further still, coding advanced loops right from the command line, or within Bash scripts.

Harnessing this power, one can manipulate any document, any set of files, or implement advanced algorithms of almost any type and flavor. You are unlikely to run into any limitations if you use Bash as the basis for your scripting, and Bash loops form a powerful part of this.

That said, Bash loops sometimes can be tricky in terms of syntax and surrounding knowledge is paramount. Today we present with you a set of bash loop examples to help you upskill quickly and become Bash loop proficient! Let’s get started!

In this tutorial you will learn:

How Bash for, while and until based loops work, with examples
How Bash requires terminating of loop-starting statements before the do…done section of the loop can follow, and how this relates to if and other statements
How to implement basic and medium advanced bash loops
How subshells work and how they can be used inside bash loop scope declarations
How to start coding loops defensively, avoiding errors in the output
How to code one-liners (a common term used amongst Bash developers) on the command line versus implement the same code in a Bash script
How the ; syntax idiom is an important matter when it comes to coding Bash loops, both on the command line and in scripts

How to check Bash version

3 June 2020 by Lubos Rendek

Objective

This article will provide you with the information on how to check bash version on your operating system.

Operating System and Software Versions

Operating System: – Distribution Agnostic

Requirements

No special prerequisites are required is required.

How to manage the expansion of empty or unset bash variables

3 June 2020 by Egidio Docile

Objective

The object of this tutorial is to learn how to modify bash behavior when expanding unset or empty variables using dedicated syntax.

Requirements

No special system privileges are required to follow this tutorial

How to Change Bash Prompt

3 June 2020 by Luke Reynolds

The “Bash prompt” on the command line interface is that bit of text that precedes your commands. It is usually the username followed by the hostname on most systems, so the syntax might look something like user@linuxconfig$ for example. Suffice it to say, the default Bash command line prompt on many Linux systems is quite minimal.

How to use graphical widgets in bash scripts with zenity

3 June 2020 by Egidio Docile

Zenity is a very useful utility which let us create graphical user interfaces for our shell scripts. Several widgets exists, and can be used by invoking the program with the respective options. The widgets are based on the GTK toolkit, and return the result of the user interaction either on the standard output or as a return code.

In this tutorial you will learn:

What are the general zenity options
What are the some of the most useful available widgets and how to use them

How to create a selection menu using the select statement in Bash shell

3 June 2020 by Egidio Docile

We all very often use bash scripts to automatize boring and repetitive tasks. Sometimes in our scripts we need to ask
the user to perform one or more choices interactively: in this tutorial we will see how to use the Bash shell select statement to perform such operation in very few lines of code.

In this tutorial you will learn:

How to use the Bash select statement
How to customize the select menu prompt

How to use ncurses widgets in shell scripts on Linux

3 June 2020 by Egidio Docile

In this tutorial we will learn the basics of the dialog utility, in order to use ncurses widget in our shell scripts. We will see how to install dialog in the most used Linux distributions, some of the common options we can use to alter the behavior of dialog, how to use some widgets; among the others: inputbox, checklist, radiolist and yesno. Finally, we will see how to use the data obtained by the widget processing.

In this tutorial you will learn:

How to install the dialog utility on Linux
What are the most relevant dialog options
How to use the inputbox, checklist, radiolist, passwordbox, msbox, calendar and yesno widgets
How to manage data derived from the widget processing

How to set up transmission-daemon on a Raspberry Pi and control it via web interface

29 May 2020 by Egidio Docile

Introduction

Transmission is probably the most famous torrent client in the Gnu/Linux world, and it’s very often used even on other operating systems. It’s really easy to use, and its graphical interface is very intuitive; however in this tutorial we will see how to install transmission-daemon and run transmission on a headless machine: that’s an ideal setup to create a “Torrent-box”, using for example a Raspberry Pi, to reduce power usage.

Once installed and configured, we will be able to manage the application using the web interface. For the sake of this tutorial I will install transmission-daemon on a Raspberry Pi, using the Raspbian operating system, however the same instructions should work on Ubuntu and Debian.