Bash Script to Validate Email Address with Regex

Use a Bash script with a regex pattern like ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ inside an if [[ $email =~ regex ]]; then condition to validate an email address.

Examples

[e-mail]

OutputValid email address

[e-mail]

OutputValid email address

Inputinvalid-email@.com

OutputInvalid email address

How to Think About It

To validate an email in Bash, check if the input matches a pattern that includes allowed characters before and after the '@' symbol, and ends with a valid domain suffix. Use a regular expression to test this pattern inside an if statement.

Algorithm

1

Get the email address input from the user or variable.

2

Define a regex pattern that matches valid email formats.

3

Check if the email matches the regex pattern.

4

If it matches, print 'Valid email address'.

5

Otherwise, print 'Invalid email address'.

Code

bash

#!/bin/bash

email="$1"
regex='^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'

if [[ $email =~ $regex ]]; then
  echo "Valid email address"
else
  echo "Invalid email address"
fi

Output

Valid email address

Dry Run

Let's trace '[e-mail]' through the code

1

Input email

email='[e-mail]'

2

Regex pattern

regex='^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'

3

Match check

'[e-mail]' matches regex -> true

Step	Email	Regex Match
1	[e-mail]	true

Why This Works

Step 1: Regex pattern meaning

The regex ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$ ensures the email starts with allowed characters, has an '@', then a domain and a valid suffix.

Step 2: Using Bash regex match

The [[ $email =~ $regex ]] syntax tests if the email matches the pattern, returning true or false.

Step 3: Conditional output

If the match is true, the script prints 'Valid email address'; otherwise, it prints 'Invalid email address'.

Alternative Approaches

Using grep with regex

bash

#!/bin/bash
email="$1"
if echo "$email" | grep -Eq '^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'; then
  echo "Valid email address"
else
  echo "Invalid email address"
fi

Uses external grep command; slightly slower but compatible with older Bash versions.

Using Perl for validation

bash

#!/bin/bash
email="$1"
if perl -e 'exit($ARGV[0] =~ /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/ ? 0 : 1)' "$email"; then
  echo "Valid email address"
else
  echo "Invalid email address"
fi

More powerful regex support but requires Perl installed.

Complexity: O(n) time, O(1) space

Time Complexity

The regex match scans the email string once, so time complexity is linear in the length of the email.

Space Complexity

The script uses a fixed amount of memory for variables and regex, so space complexity is constant.

Which Approach is Fastest?

Bash's built-in regex matching is fastest; grep and Perl add overhead by calling external programs.

Approach	Time	Space	Best For
Bash regex match	O(n)	O(1)	Simple scripts, fast execution
grep with regex	O(n)	O(1)	Compatibility with older Bash versions
Perl regex	O(n)	O(1)	Complex regex needs, powerful validation