Accidentally changed cksum behavior with the -P flag, toggle its meaning.
diff --git a/toys/cksum.c b/toys/cksum.c
index 9b61667..69609a2 100644
--- a/toys/cksum.c
+++ b/toys/cksum.c
@@ -18,7 +18,7 @@
 	  If no files listed, copy from stdin.  Filename "-" is a synonym for stdin.
 
 	  -L	Little endian (defaults to big endian)
-	  -P	Skip pre-inversion
+	  -P	Pre-inversion
 	  -I	Skip post-inversion
 	  -N	No length
 */
@@ -43,7 +43,7 @@
 
 static void do_cksum(int fd, char *name)
 {
-	unsigned crc = (toys.optflags&4) ? 0 : 0xffffffff;
+	unsigned crc = (toys.optflags&4) ? 0xffffffff : 0;
 	uint64_t llen = 0, llen2;
 	unsigned (*cksum)(unsigned crc, unsigned char c);