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/syscall.h b/syscall.h
index c89d5a3..4efd255 100644
--- a/syscall.h
+++ b/syscall.h
@@ -15,4 +15,6 @@
 #define SYS_mkdir 16
 #define SYS_chdir 17
 #define SYS_dup 18
+#define SYS_getpid 19
+#define SYS_sbrk 20