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

Link: https://leetcode.com/problems/valid-phone-numbers/description/

思路

固定的格式，拆解开来

• 3个数字 + ‘-’，或者，'(' + 三个数字 + ')' + ' '
• 3个数字 + '-'
• 4个数字

根据这三个规则直接写正则表达式代码即可

代码

awk '/^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/' file.txt

注意在在正则表达式的首尾表示是开头和结尾