--- /n/sources/plan9/sys/src/cmd/cpu.c	Sun Apr 14 16:33:20 2019
+++ /sys/src/cmd/cpu.c	Tue Jun 23 00:00:00 2026
@@ -425,14 +425,12 @@
 {
 	int n;
 
-	while(len) {
+	while(len--) {
 		n = read(fd, str, 1);
-		if(n < 0) 
-			return -1;
-		if(*str == '\0')
+		if(n <= 0)
+			break;
+		if(*str++ == '\0')
 			return 0;
-		str++;
-		len--;
 	}
 	return -1;
 }