Bash: Variables

Variables are used to store data, like text or numbers, that you can use later in your script.

Defining Variables

Basic variable definition

my_string="Hello World"

To define a variable, use `name="value"`. Note that there should be no spaces around the equals sign.

Integer and floating-point variables

 my_integer=10
 my_float=10.5

Numbers can be assigned directly without quotes. Bash treats all variables as strings by default, but you can perform arithmetic operations on integers using `((...))`.

Accessing and Printing Variables

Accessing a variable

echo $my_string

To use the value stored in a variable, precede its name with a dollar sign `$`. The `echo` command prints the value to the terminal.

Concatenating Strings

Combining variables and strings

full_name="John Doe" echo "My name is $full_name"

Bash automatically concatenates adjacent strings and variables. You can combine multiple variables or mix them with regular text inside double quotes.

Exporting Variables

The `export` keyword

export my_variable="Some Value"

The `export` keyword makes a variable available to child processes or scripts. Without `export`, a variable is only available in the current shell session.

Arithmetic Operations

Performing arithmetic with variables

 a=5
 b=3
 sum=$((a + b))
 echo "Sum: $sum"

You can perform arithmetic operations using the $((...)) syntax. Bash supports addition +, subtraction -, multiplication *, division /, and more for integer variables.

Getting Length of a String

Find the length of a string variable

 my_string="Hello World"
 echo ${#my_string}

To get the length of a string stored in a variable, use ${#variable_name}. This returns the number of characters in the string.