Hi folks, this article is meant to be a really short introduction to Bash.

First, what is Bash? Bash is a Unix shell and command language developed by Brian Fox for the GNU Project as a free software replacement for the Bourne shell [1]. Bash is the default shell on most Linux and macOS systems. Bash has even been ported to Windows as it is supported natively in Windows 10 and through Cygwin and MinGW. A Bash script is a file containing one or commands and can be very useful to automate commands that you may otherwise have to type out yourself each time on a terminal. Without further ado, let’s dive in.

Interpreter Directive

A common way to write Bash scripts is to add an interpreter directive as the first line of the file, e.g.
#!/bin/bash

This way, once the file is made executable, a user can execute the file directly from a terminal and it will be executed with Bash automatically.

Variable assignment

Variable assignment is done as follows:

x="some tuff"

Note that there shouldn’t be space between the letter and the = sign.

Referencing variables
y=$x

E.g.

x=5
y=$x
echo y is $y

If conditions

Here is an example of how to write an if statement.

if [ $x == "some stuff" ]
then
echo some stuff
fi

If/else conditional statement

if [ $x == "stuff" ]
then
echo some stuff
else
echo some other stuff
fi

If/else if/else clause

if [ $x == "foo" ]
then
echo some stuff
elif [ $x == "bar" ]
then
echo some other stuff
else
echo the last stuff
fi

Arrays
myArray=(1 2 3)

While Loop Through an Array

myArray=(1 2 3)
count=0
while [ "x${myArray[count]}" != "x" ]
do
echo element is ${myArray[count]}
count=$(( $count + 1 ))
done

You can find much more details in Mike G’s excellent BASH Programming website [2].

References

1. Bash (Unix shell) – Wikipedia. view-source:https://en.wikipedia.org/wiki/Bash_(Unix_shell) [16/02/17].

2. BASH Programming – Introduction HOW-TO. http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html [16/02/17].