i/o redirection in sh

better parsing of sh commands (copied from jos sh)
cat: read from 1 if no args
sbrk system call, but untested
getpid system call
moved locks in keyboard intr, but why do we get intr w. null characters from keyboard?

1 files changed, 2 insertions, 0 deletions

diff --git a/echo.c b/echo.c
index 5d0c5a4..7bf3a45 100644
--- a/echo.c
+++ b/echo.c
@@ -1,3 +1,5 @@
+#include "types.h"
+#include "stat.h"
 #include "user.h"
 
 int