[LeetCode] 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.

For 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

考察Linux查找文本的操作，主要是命令与正则表达式

# Read from the file file.txt and output all valid phone numbers to stdout.
# No.1
grep -e "^[0-9]\{3\}-[0-9]\{3\}-[0-9]\{4\}$" -e "^([0-9]\{3\}) [0-9]\{3\}-[0-9]\{4\}$" file.txt

# No.2
grep -e "^\([0-9]\{3\}-\|([0-9]\{3\}) \)[0-9]\{3\}-[0-9]\{4\}$" file.txt