From 8c12928cc59b5a0b1d9aa6aada2772d0d2320542 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Thu, 25 Jul 2019 06:50:12 -0400
Subject: [PATCH] First draft of first lab assignment?

---
 labs/xv6.html | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/labs/xv6.html b/labs/xv6.html
index fcbb234..2f6a4ae 100644
--- a/labs/xv6.html
+++ b/labs/xv6.html
@@ -178,6 +178,44 @@ initial file system.  You just ran one of them: <tt>ls</tt>.
     <li>Don't recurse into "." and "..".
   </ul>
 
+<p>Optional: support regular expressions in name matching.  Grep has some
+  primitive support for regular expressions.
+  
+<h2>xargs</h2>
+
+<p>Write a simple version of the UNIX xargs program: read lines from
+  standard in and run a command for each line, supplying the line as
+  arguments to the command.  The following example illustrates xarg's
+  behavior:
+  <pre>
+    $ xargs echo bye
+    hello too
+    bye hello too
+    <ctrl-d>
+    $
+  </pre>
+  Note that the command here is "echo bye" and the additional
+  arguments are "hello too", making the command "echo bye hello too",
+  which outputs "bye hello too".
+  
+<p>xargs and find combine well:
+  <pre>
+    find . b | xargs grep hello
+  </pre>
+  will run "grep hello" on each file named b in the directories below ".".
+
+<p>Some hints:
+  <ul>
+    <li>Use <tt>fork</tt> and <tt>exec</tt> system call to invoke the
+      command on each line of input.  Use <tt>wait</tt> in the parent
+      to wait for the child to complete running the command.
+    <li>Read from stdin a character at the time until the newline
+      character ('\n').
+    <li>kernel/param.h declares MAXARG, which may be useful if you need
+    to declare an argv.
+  </ul>
+
+
 <h2>Optional: modify the shell</h2>
 
 <p>Modify the shell to support wait.