[PATCH] dd doesn't return a failure status

[Kazuo TAKADA]

Hi,

If the dd command fails in a sequence of copying, it always returns
EXIT_SUCCESS.  So, I can't judge whether the command had succeeded or
failed.

Its behavior doesn't conform to POSIX.

  POSIX 1003.1:
  http://www.opengroup.org/onlinepubs/009695399/utilities/dd.html
  | EXIT STATUS
  | The following exit values shall be returned:
  |
  |  0
  |     The input file was copied successfully.
  | >0
  |     An error occurred.

For example, copy some data to a small size device repeatly.

--------------------------------------------------
(with a root account)
# ./busybox dd if=/dev/zero of=/dev/ram
dd: writing '/dev/ram': No space left on device
32769+0 records in
32768+0 records out
# echo $?
0			<= should be failed!!

# ./busybox dd if=/dev/zero of=/dev/ram count=1
1+0 records in
1+0 records out
# echo $?
0

# /bin/dd if=/dev/zero of=/dev/ram	<= GNU's one
dd: writing to `/dev/ram': No space left on device
32769+0 records in
32768+0 records out
# echo $?
1
--------------------------------------------------

The old busybox-1.2.2.1 returns EXIT_FAILURE.  It is the version that
dd had not reconstructed yet.

Can you accept the patch below?
write_and_stats() is the function which returns a bool value.

----------------------------------------------------------------------
--- coreutils/dd.c.orig	2007-09-03 20:48:39.000000000 +0900
+++ coreutils/dd.c	2007-10-03 10:31:50.000000000 +0900
@@ -106,7 +106,7 @@
 #endif
 	};
 	size_t ibs = 512, obs = 512;
-	ssize_t n, w;
+	ssize_t n, w = 0;
 	char *ibuf, *obuf;
 	/* And these are all zeroed at once! */
 	struct {
@@ -303,13 +303,17 @@
 				tmp += d;
 				oc += d;
 				if (oc == obs) {
-					if (write_and_stats(ofd, obuf, obs, obs, outfile))
+					if (write_and_stats(ofd, obuf, obs, obs, outfile)) {
+						w = -1;
 						goto out_status;
+					}
 					oc = 0;
 				}
 			}
-		} else if (write_and_stats(ofd, ibuf, n, obs, outfile))
+		} else if (write_and_stats(ofd, ibuf, n, obs, outfile)) {
+			w = -1;
 			goto out_status;
+		}
 	}
 
 	if (ENABLE_FEATURE_DD_IBS_OBS && oc) {
@@ -330,5 +334,5 @@
  out_status:
 	dd_output_status(0);
 
-	return EXIT_SUCCESS;
+	return (w >= 0 ? EXIT_SUCCESS : EXIT_FAILURE);
 }
----------------------------------------------------------------------

Best regards,
Kazuo TAKADA