Add Grep For Files Without A Match as a unix til.

unix/grep-for-files-without-a-match.md

@@ -0,0 +1,14 @@
+# Grep For Files Without A Match
+
+The `grep` command is generally used to find files whose contents match a
+pattern. With the `-L` (`--files-without-match`) flag, `grep` can be used to
+find files that don't match the given pattern.
+
+For instance, to find files in the current directory that don't have
+`foobar` anywhere in their content, run:
+
+```bash
+$ grep -L "foobar" ./*
+```
+
+[source](http://stackoverflow.com/questions/1748129/using-grep-to-find-files-that-dont-contain-a-given-string-pattern)