题目
- 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
解法１
# Read from the file file.txt and output all valid phone numbers to stdout.
cat file.txt | grep -P '(^\(\d{3}\) \d{3}-\d{4}$)|(^\d{3}-\d{3}-\d{4}$)'
grep -P '^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$' file.txt
-
\转义符: to escape next one trailing character
-P, --perl-regexp Interpret the pattern as a Perl-compatible regular expression (PCRE). This is experimental and grep -P may warn of unimplemented features.
解法２
sed -n -r '/^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/p' file.txt
-n, --quiet, --silent suppress automatic printing of pattern space
-E, -r, --regexp-extended use extended regular expressions in the script (for portability use POSIX -E).
解法３
awk '/^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/' file.txt
引用和推荐阅读：
https://leetcode.com/problems/valid-phone-numbers/
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