ValidPhoneNumbers.sh

# Source : https://leetcode.com/problems/valid-phone-numbers
# Author : Dean Shi
# Date   : 2017-09-05

##################################################################################
#
#  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
#
##################################################################################

#!/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