shell/ValidPhoneNumbers.sh

# Source : https://leetcode.com/problems/valid-phone-numbers/
# Author : Hao Chen
# Date   : 2015-03-31

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# 
# Given a text file file.txt that contains 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.
# 
# For 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
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#!/bin/sh


# 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