BashVariables

Understanding Variables in Bash

Variables in Bash are used to store data that can be used and manipulated throughout your script or command-line session. Bash variables are untyped, meaning they can hold any type of data.

Declaring Variables

Variables are declared by simply assigning a value to a name. There should be no spaces around the equal sign:

• variable_name=value
• To access the value of a variable, prefix it with a dollar sign:$variable_name

name="John Doe"echo "Hello, $name!"number=42echo "The number is $number"

Environment Variables

Environment variables are special variables that affect the way processes run on your system. They are often used to store system-wide values like the location of executables or the default editor.

# Display the PATH environment variableecho "Your PATH is $PATH"

Local vs. Global Variables

Local variables are only available within the block of code in which they are defined, such as within a function. Global variables are accessible from anywhere in the script.

# Define a local variable in a functionmy_function() {  local local_var="I am local"  echo $local_var}my_function

Common Variable Operations

Variables can be used in various operations, such as concatenation and arithmetic.

• Concatenation: Combine strings using variables.
• Arithmetic: Perform calculations using variables.

# Concatenationgreeting="Hello, "name="World"echo "$greeting$name"# Arithmeticnum1=5num2=10sum=$((num1 + num2))echo "The sum is $sum"