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Question
Formatted question description: https://leetcode.ca/all/193.html
Given a text file file.txt that contains a 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
Algorithm
Regex.
^: indicates the starting of the string
$: indicates the end of the string
[0-9]\{3\} or d{3}: represent 3 numbers (\{3\}) between the range 0-9 ([0-9] a digit in the range)
\: suppresses the specialness of the character
-P: Interpret PATTERNS as Perl-compatible regular expressions
Code
Shell
grep -P '^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$' file.txt