diff --git a/docs/CommandGuide/extract.html b/docs/CommandGuide/extract.html
index 36f01e4..b42aec2 100644
--- a/docs/CommandGuide/extract.html
+++ b/docs/CommandGuide/extract.html
@@ -20,7 +20,7 @@
 SYNOPSIS
 </h3>
 
-extract [options] &lt;filename&gt; [filename ...]
+extract [options] [filename]
 <h3>
 DESCRIPTION
 </h3>
@@ -28,6 +28,14 @@
 The extract command takes the name of a function and extracts it from the
 specified LLVM bytecode file.  It is primarily used as a debugging tool to
 reduce test cases from larger programs that are triggering a bug.
+<p>
+
+In addition to extracting the bytecode of the specified function, extract will
+also remove unreachable global variables, prototypes, and unused types.
+<p>
+
+The extract command will read its input from standard input if filename is
+omitted or if filename is -.  The output is always written to standard output.
 
 <h3>
 OPTIONS