Problem Statement:
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.
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
Solution:
grep -P ‘^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$’ file.txt
^ denotes the start of the string.
$ denotes the end of the string.
\d means numbers
{3} means 3 numbers and {4} means 4 numbers
(A)|(B) means match pattern A or pattern B
\( escapes the bracket
