Valid Phone Numbers Problem & Solution

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, where x means a digit. You may also assume each line in the text file must not contain leading or trailing white spaces.

See the valid phone numbers problem on LeetCode.

Bash Solution

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