Leetcode no. 193

193. Valid Phone Numbers

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

# Read from the file file.txt and output all valid phone numbers to stdout.
awk '/^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/' file.txt

或者
sed -n -r '/^[0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/p' file.txt

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