doc: dd: document that the default block size is 512 bytes

* src/dd.c (usage): Document the default block size.
* doc/coreutils.texi (dd invocation): Document that the default
block size (bs, ibs, obs) is 512 bytes.
Reported by Petr Uzel.

3 files changed, 6 insertions, 3 deletions

diff --git a/THANKS b/THANKS
index bedb01a7a..f2fcd0175 100644
--- a/THANKS
+++ b/THANKS
@@ -446,6 +446,7 @@ Peter Moulder                       reiter@netspace.net.au
 Peter O'Gorman                      bug-coreutils@mlists.thewrittenword.com
 Peter Samuelson                     psamuels@sampo.creighton.edu
 Peter Seebach                       seebs@taniemarie.solon.com
+Petr Uzel                           petr.uzel@suse.cz
 Petter Reinholdtsen                 pere@hungry.com
 Phelippe Neveu                      pneveu@pcigeomatics.com
 Phil Richards                       phil.richards@vf.vodafone.co.uk
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 42234d36a..8d496ad37 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7605,6 +7605,7 @@ bytes (or the size specified with @samp{seek=}).
 @cindex input block size
 Set the input block size to @var{bytes}.
 This makes @command{dd} read @var{bytes} per block.
+The default is 512 bytes.
 
 @item obs=@var{bytes}
 @opindex obs
@@ -7612,6 +7613,7 @@ This makes @command{dd} read @var{bytes} per block.
 @cindex output block size
 Set the output block size to @var{bytes}.
 This makes @command{dd} write @var{bytes} per block.
+The default is 512 bytes.
 
 @item bs=@var{bytes}
 @opindex bs
diff --git a/src/dd.c b/src/dd.c
index 4604ced9a..6837b7b90 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -463,16 +463,16 @@ Usage: %s [OPERAND]...\n\
       fputs (_("\
 Copy a file, converting and formatting according to the operands.\n\
 \n\
-  bs=BYTES        read and write BYTES bytes at a time\n\
+  bs=BYTES        read and write BYTES bytes at a time (also see ibs=,obs=)\n\
   cbs=BYTES       convert BYTES bytes at a time\n\
   conv=CONVS      convert the file as per the comma separated symbol list\n\
   count=BLOCKS    copy only BLOCKS input blocks\n\
-  ibs=BYTES       read BYTES bytes at a time\n\
+  ibs=BYTES       read BYTES bytes at a time (default: 512)\n\
 "), stdout);
       fputs (_("\
   if=FILE         read from FILE instead of stdin\n\
   iflag=FLAGS     read as per the comma separated symbol list\n\
-  obs=BYTES       write BYTES bytes at a time\n\
+  obs=BYTES       write BYTES bytes at a time (default: 512)\n\
   of=FILE         write to FILE instead of stdout\n\
   oflag=FLAGS     write as per the comma separated symbol list\n\
   seek=BLOCKS     skip BLOCKS obs-sized blocks at start of output\n\