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.

Solution

The problem Valid Phone Numbers can be solved by using regex with grep.

Implementation

# Read from the file file.txt and output all valid phone numbers to stdout.

grep -P '^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$' file.txt