Is there a way to search a file looking for two or more words that appear in the file?

<p>I'm looking to "grep" a file looking for matches only if 2 or more of the keywords are found.</p> <p>So, for example, I want to search a file for blah and foo but they are on separate lines of the file. I only want to know if the file contains both keywords. I realize grep may not be the solution for this; may need to write a script of some sort but grep or some equivalent would be much faster.</p> <p>More Info:</p> <p>I have a file that contains:</p> <pre><code>stuff blah explore morestuff explore here foo </code></pre> <p>I want to be able to search that file for to see if both blah and foo appear in the file.</p>