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

給定一個包含電話號碼列表（一行一個電話號碼）的文字檔案 file.txt，寫一個 bash 指令碼輸出所有有效的電話號碼。

你可以假設一個有效的電話號碼必須滿足以下兩種格式： (xxx) xxx-xxxx 或 xxx-xxx-xxxx。（x 表示一個數字）

你也可以假設每行前後沒有多餘的空格字元。

示例:

假設 file.txt 內容如下：

987-123-4567
123 456 7890
(123) 456-7890

你的指令碼應當輸出下列有效的電話號碼：

987-123-4567
(123) 456-7890

8ms

1 # Read from the file file.txt and output all valid phone numbers to stdout.
2 grep -P '^(\d{3}-|\(\d{3}\) )\d{3}-\d{4}$' file.txt

12ms

1 # Read from the file file.txt and output all valid phone numbers to stdout.
2 
3 grep -P '^\([0-9]{3}\)\s[0-9]{3}-[0-9]{4}$|^[0-9]{3}-[0-9]{3}-[0-9]{4}$' file.txt

12ms

1 # Read from the file file.txt and output all valid phone numbers to stdout.
2 sed -n -r '/^([0-9]{3}-|\([0-9]{3}\) )[0-9]{3}-[0-9]{4}$/p' file.txt

12ms

1 # Read from the file file.txt and output all valid phone numbers to stdout.
2 egrep "(^[0-9]{3}-[0-9]{3}-[0-9]{4}$)|(^\([0-9]{3}\)\s[0-9]{3}-[0-9]{4}$)" file.txt