Regex in [[ ]] with =~ in Bash Scripting - Mini Project: Build & Apply

Using Regex in Bash with [[ ]] and =~

📖 Scenario: You work in a small company where you need to check if user input matches certain patterns. You want to automate this check using a Bash script.

🎯 Goal: Build a Bash script that uses the [[ ]] test with the =~ operator to check if a string matches a regular expression pattern.

📋 What You'll Learn

Create a variable with a specific string value

Create a regex pattern variable to match a pattern

Use the [[ ]] test with =~ to check if the string matches the regex

Print a message showing if the string matches or not

💡 Why This Matters

🌍 Real World

Checking if user input or file names match expected patterns is common in scripts that automate tasks like validation or filtering.

💼 Career

Many IT and DevOps roles require writing Bash scripts that validate data formats using regex to automate system checks and data processing.

1

Create a string variable

Create a variable called input_string and set it to the exact value "hello123".

Bash Scripting

# Create the variable input_string with value "hello123"
# Your code here

Need a hint?

Use variable_name="value" syntax to create a string variable in Bash.

2

Create a regex pattern variable

Create a variable called pattern and set it to the regex ^[a-z]+[0-9]+$ which matches strings starting with letters followed by numbers.

Bash Scripting

input_string="hello123"
# Create the variable pattern with regex ^[a-z]+[0-9]+$
# Your code here

Need a hint?

Use single quotes to store the regex pattern as a string in Bash.

3

Use [[ ]] with =~ to test the regex

Write an if statement using [[ $input_string =~ $pattern ]] to check if input_string matches pattern. Inside the if, set a variable result to "Match", else set result to "No match".

Bash Scripting

input_string="hello123"
pattern='^[a-z]+[0-9]+$'
# Use if [[ $input_string =~ $pattern ]] to check match
# Set result="Match" if true, else result="No match"
# Your code here

Need a hint?

Use if [[ $var =~ $regex ]]; then ... else ... fi syntax in Bash.

4

Print the result

Write a echo command to print the value of the result variable.

Bash Scripting

input_string="hello123"
pattern='^[a-z]+[0-9]+$'
if [[ $input_string =~ $pattern ]]; then
    result="Match"
else
    result="No match"
fi
# Print the result variable
# Your code here

Need a hint?

Use echo "$result" to print the variable's value.