#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.

#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.
cat file.txt | grep -P "^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$"
