my solution to lab5

lab/user/cat.c

@@ -0,0 +1,36 @@
+#include <inc/lib.h>
+
+char buf[8192];
+
+void
+cat(int f, char *s)
+{
+	long n;
+	int r;
+
+	while ((n = read(f, buf, (long)sizeof(buf))) > 0)
+		if ((r = write(1, buf, n)) != n)
+			panic("write error copying %s: %e", s, r);
+	if (n < 0)
+		panic("error reading %s: %e", s, n);
+}
+
+void
+umain(int argc, char **argv)
+{
+	int f, i;
+
+	binaryname = "cat";
+	if (argc == 1)
+		cat(0, "<stdin>");
+	else
+		for (i = 1; i < argc; i++) {
+			f = open(argv[i], O_RDONLY);
+			if (f < 0)
+				printf("can't open %s: %e\n", argv[i], f);
+			else {
+				cat(f, argv[i]);
+				close(f);
+			}
+		}
+}