"content":"<p>Given a text file <code>file.txt</code> that contains a list of phone numbers (one per line), write a one-liner bash script to print all valid phone numbers.</p>\n\n<p>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)</p>\n\n<p>You may also assume each line in the text file must not contain leading or trailing white spaces.</p>\n\n<p><strong>Example:</strong></p>\n\n<p>Assume that <code>file.txt</code> has the following content:</p>\n\n<pre>\n987-123-4567\n123 456 7890\n(123) 456-7890\n</pre>\n\n<p>Your script should output the following valid phone numbers:</p>\n\n<pre>\n987-123-4567\n(123) 456-7890\n</pre>\n",