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, 22 insertions, 13 deletions

diff --git a/cat.c b/cat.c
index 8154ae2..631bd09 100644
--- a/cat.c
+++ b/cat.c
@@ -1,17 +1,32 @@
+#include "types.h"
+#include "stat.h"
 #include "user.h"
 
 char buf[513];
 
-int
-main(int argc, char *argv[])
+void
+rfile(int fd)
 {
-  int fd, i, cc;
+  int cc;
 
-  if(argc < 2){
-    puts("Usage: cat files...\n");
+  while((cc = read(fd, buf, sizeof(buf) - 1)) > 0){
+    buf[cc] = '\0';
+    puts(buf);
+  }
+  if(cc < 0){
+    puts("cat: read error\n");
     exit();
   }
+}
+
+int
+main(int argc, char *argv[])
+{
+  int fd, i;
 
+  if (argc <= 1) {
+    rfile(0);
+  } else {
   for(i = 1; i < argc; i++){
     fd = open(argv[i], 0);
     if(fd < 0){
@@ -20,16 +35,10 @@ main(int argc, char *argv[])
       puts("\n");
       exit();
     }
-    while((cc = read(fd, buf, sizeof(buf) - 1)) > 0){
-      buf[cc] = '\0';
-      puts(buf);
-    }
-    if(cc < 0){
-      puts("cat: read error\n");
-      exit();
-    }
+    rfile(fd);
     close(fd);
   }
+  }
 
   exit();
 }