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