Valid Phone Numbers

PROBLEM

Given a text file file.txt that contains a list of phone numbers (one per line), write a one-liner bash script to print all valid phone numbers.

You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)

You may also assume each line in the text file must not contain leading or trailing white spaces.

Example:

Assume that file.txt has the following content:

987-123-4567
123 456 7890
(123) 456-7890

Your script should output the following valid phone numbers:

987-123-4567
(123) 456-7890

SOLVING

We’ll use Regex to solve this problem

Steps

Just use a Regex to check your file, ^(\([0-9]{3}\)\s|[0-9]{3}-)[0-9]{3}-[0-9]{4}$

Code

grep -E "^(\([0-9]{3}\)\s|[0-9]{3}-)[0-9]{3}-[0-9]{4}$" file.txt

PROBLEM