Re: [PATCH] Re: dd blocks/bytes at a time

[Paul Eggert]

Jim Meyering <address@hidden> writes:

> Andreas Schwab <address@hidden> wrote:
>> But only the preceding ones.
>
> True.  Thanks.

Wait a minute -- POSIX says bs= should override all ibs= and obs=
operands (not just preceding ones), and traditional dd conforms to
POSIX here.  So the GNU documentation was right and the behavior
wrong.

Here's a patch.

2006-12-21  Paul Eggert  <address@hidden>

        * NEWS: dd bs= operands now silently override later ibs= and obs=,
        as POSIX requires.
        * src/dd.c (scanargs): Implement it.
        * tests/dd/misc (outbytes): Test it.
        * doc/coreutils.texi (dd invocation): Specify that bs=N
        overrides later ibs and obs, undoing part of the
        previous change.  (The behavior was wrong.)

diff --git a/NEWS b/NEWS
index bf1d287..c934cd9 100644
--- a/NEWS
+++ b/NEWS
@@ -14,6 +14,9 @@ GNU coreutils NEWS
   more file arguments.  This was due to a double-free bug, introduced
   in coreutils-5.3.0.

+  dd bs= operands now silently override any later ibs= and obs=
+  operands, as POSIX and tradition require.
+
   A cross-partition "mv /etc/passwd ~" (by non-root) now prints
   a reasonable diagnostic.  Before, it would print this:
   "mv: cannot remove `/etc/passwd': Not a directory".
diff --git a/src/dd.c b/src/dd.c
index 35c0a43..f37445e 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -877,6 +877,7 @@ static void
 scanargs (int argc, char **argv)
 {
   int i;
+  size_t blocksize = 0;

   for (i = optind; i < argc; i++)
     {
@@ -927,7 +928,7 @@ scanargs (int argc, char **argv)
          else if (STREQ (name, "bs"))
            {
              invalid |= ! (0 < n && n <= MAX_BLOCKSIZE (INPUT_BLOCK_SLOP));
-             output_blocksize = input_blocksize = n;
+             blocksize = n;
            }
          else if (STREQ (name, "cbs"))
            {
@@ -952,6 +953,9 @@ scanargs (int argc, char **argv)
        }
     }

+  if (blocksize)
+    input_blocksize = output_blocksize = blocksize;
+
   /* If bs= was given, both `input_blocksize' and `output_blocksize' will
      have been set to positive values.  If either has not been set,
      bs= was not given, so make sure two buffers are used. */
diff --git a/tests/dd/misc b/tests/dd/misc
index 2db5c5b..513221b 100755
--- a/tests/dd/misc
+++ b/tests/dd/misc
@@ -74,6 +74,9 @@ if dd oflag=nolinks if=$tmp_in of=$tmp_o
   dd oflag=nolinks < $tmp_in > $tmp_out 2>&1 || fail=1
 fi

+outbytes=`echo x | dd bs=3 ibs=10 obs=10 conv=sync 2>/dev/null | wc -c`
+test "$outbytes" -eq 3 || fail=1
+
 rm -f $tmp_in $tmp_in2 $tmp_sym $tmp_out

 exit $fail
M ChangeLog
M NEWS
M src/dd.c
M tests/dd/misc
Committed as 40bc2cf02aeb0d1ae4a9754b01a0f989c974e4e1

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index dfd9595..ab95db4 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7170,7 +7170,7 @@ This makes @command{dd} write @var{bytes
 @cindex block size
 Set both input and output block sizes to @var{bytes}.
 This makes @command{dd} read and write @var{bytes} per block,
-overriding any preceding @samp{ibs} and @samp{obs} settings.
+overriding any @samp{ibs} and @samp{obs} settings.

 @item address@hidden
 @opindex cbs
M doc/ChangeLog
M doc/coreutils.texi
Committed as 6c92651bd3435131f09fb5b7d01f1826fabc3a07