Problem#
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.
Examples#
Example:
Assume that file.txt has the following content:
1
2
3
|
987-123-4567
123 456 7890
(123) 456-7890
|
Your script should output the following valid phone numbers:
1
2
|
987-123-4567
(123) 456-7890
|
Solution#
Method 1 - Using Regex#
Code#
1
2
3
|
grep "^\(([0-9]\{3\}) \|[0-9]\{3\}-\)[0-9]\{3\}-[0-9]\{4\}$" file.txt # Basic
grep -E "^(\([0-9]{3}\) |^[0-9]{3}-)[0-9]{3}-[0-9]{4}$" file.txt # Extended Grep using -E
grep -P "^(\(\d{3}\) |\d{3}-)\d{3}-\d{4}$" file.txt # Perl flavoured Grep using -P
|
1
|
What in these parentheses should come in the beginning.
|
1
|
grep -P ‘^(\d{3}-|\(\d{3}\) )’
|
1
2
|
`\(\d{3}\) )`’ = `\d{3}\` means it should contain 3 digit and a space
|
1
|
grep -P ‘^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}’
|