my solution to lab5

lab/user/num.c

@@ -0,0 +1,47 @@
+#include <inc/lib.h>
+
+int bol = 1;
+int line = 0;
+
+void
+num(int f, const char *s)
+{
+	long n;
+	int r;
+	char c;
+
+	while ((n = read(f, &c, 1)) > 0) {
+		if (bol) {
+			printf("%5d ", ++line);
+			bol = 0;
+		}
+		if ((r = write(1, &c, 1)) != 1)
+			panic("write error copying %s: %e", s, r);
+		if (c == '\n')
+			bol = 1;
+	}
+	if (n < 0)
+		panic("error reading %s: %e", s, n);
+}
+
+void
+umain(int argc, char **argv)
+{
+	int f, i;
+
+	binaryname = "num";
+	if (argc == 1)
+		num(0, "<stdin>");
+	else
+		for (i = 1; i < argc; i++) {
+			f = open(argv[i], O_RDONLY);
+			if (f < 0)
+				panic("can't open %s: %e", argv[i], f);
+			else {
+				num(f, argv[i]);
+				close(f);
+			}
+		}
+	exit();
+}
+