Show files containing "foo" and "bar" and "baz"

Explanation

Most people familiar with extended regular expressions know you can use the pipe symbol | to represent "or", so to see files containing any of "foo", "bar", or "baz" you could run:

grep -Elr 'foo|bar|baz' *

There is no corresponding symbol representing "and", but you can achieve the same effect by nesting invocations to grep. grep -lr 'foo' * returns a list of filenames in or below the current directory containing "foo". Via the $( ... ) syntax, this list is then operated on by grep -l 'bar', returning a list of filenames containing both 'foo' and 'bar', which finally is operated on by grep -l "baz". The end result is a list of filenames containing all three terms.