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dd(1M)									dd(1M)

NAME    [Toc]    [Back]

     dd	- convert and copy a file

SYNOPSIS    [Toc]    [Back]

     dd	[option=value] ...

DESCRIPTION    [Toc]    [Back]

     dd	copies the specified input file	to the specified output	with possible
     conversions.  The standard	input and output are used by default.  The
     input and output block sizes can be specified to take advantage of	raw
     physical I/O.  dd processes supplementary code-set	characters according
     to	the locale specified in	the LC_CTYPE environment variable (see LANG in
     environ(5)), except as noted below.

     Option	    Values

     if=file	    Input filename; standard input is default.

     of=file	    Output filename; standard output is	default.

     ibs=n	    Input block	size is	n bytes	(default 512).

     obs=n	    Output block size is n bytes (default 512).

     bs=n	    Set	both input and output block size, superseding ibs and
		    obs.  Also,	if no conversion is specified, preserve	the
		    input block	size instead of	packing	short blocks into the
		    output buffer (this	is particularly	efficient since	no
		    in-core copy need be done).

     cbs=n	    Conversion buffer size (logical record length).

     files=n	    Copy and concatenate n input files before terminating
		    (makes sense only where input is a magnetic	tape or
		    similar device).

     skip=n	    Skip n input blocks	before starting	copy (appropriate for
		    magnetic tape, where iseek is undefined).

     iseek=n	    Seek n blocks from beginning of input file before copying
		    (appropriate for disk files, where skip can	be slow).

     oseek=n	    Seek n blocks from beginning of output file	before
		    copying.  Preserves	the contents (over the range of	the
		    seek) of a previously existing output file.

     seek=n	    Identical to oseek,	retained for backward compatibility.

     count=n	    Copy only n	input blocks.

									Page 1

dd(1M)									dd(1M)

     conv=ascii	    Convert EBCDIC to ASCII.  Conversion results cannot	be
		    assured when supplementary code-set	characters are also
		    subject to conversion.

	  ebcdic    Convert ASCII to EBCDIC.  Conversion results cannot	be
		    assured when supplementary code-set	characters are also
		    subject to conversion.

	  ibm	    Slightly different map of ASCII to EBCDIC.	Conversion
		    results cannot be assured when supplementary code-set
		    characters are also	subject	to conversion.

     conv=block	    Convert newline-terminated ASCII records to	fixed length.

	  unblock   Convert fixed-length ASCII records to newline-terminated

	  lcase	    Map	alphabetics to lowercase.  Multibyte characters	are
		    not	converted.

	  ucase	    Map	alphabetics to uppercase.  Multibyte characters	are
		    not	converted.

	  swab	    Swap every pair of bytes.

	  noerror   Do not stop	processing on an error (limit of five
		    consecutive	errors).  A message is printed on each input
		    error, giving the statistics up to that point.

	  ignerror  Do not stop	processing on an error at all.	Unlike
		    noerror, the read errors are skipped over if possible, by
		    using lseek64(2), (if possible) and	there is no limit on
		    the	number of errors.  It is recommended that either ibs
		    or bs be used, and set to the minimum size for the input
		    device, in order to	minimize the skipped data.  This can
		    sometimes allow disk drives	to be copied even if they
		    contain unreadable blocks, although	the output copy	will
		    of course have blocks of missing (zero-filled) data.

	  notrunc   Do not truncate a pre-existing output file.

	  sync	    Pad	every input block to ibs.  Pad with spaces if
		    conv=block or conv=unblock is specified, otherwise pad
		    with nulls.

	  ..., ...  several comma-separated conversions.

     Where sizes are specified,	a number of bytes is expected.	A number can
     end with k, b, or w to specify multiplication by 1024, 512, or 2,
     respectively; a pair of numbers can be separated by x to indicate

									Page 2

dd(1M)									dd(1M)

     cbs is used only if ascii,	unblock, ebcdic, ibm, or block conversion is
     specified.	 In the	first two cases, cbs characters	are copied into	the
     conversion	buffer,	any specified character	mapping	is done, trailing
     blanks are	trimmed, and a newline is added	before sending the line	to the
     output.  In the latter three cases, characters are	read into the
     conversion	buffer and blanks are added to make up an output record	of
     size cbs.	If cbs is unspecified or zero, the ascii, ebcdic, and ibm
     options convert the character set without changing	the block structure of
     the input file; the unblock and block options become a simple file	copy.

     After completion, dd reports the number of	whole and partial input	and
     output blocks.

EXAMPLE    [Toc]    [Back]

     This command reads	an EBCDIC tape that is blocked ten 80-byte EBCDIC card
     images per	tape block into	the ASCII file x:

	  dd if=/dev/rmt/0h of=x ibs=800 obs=8k	cbs=80 conv=ascii,lcase

     Note the use of raw magnetic tape.	 dd is especially suited to I/O	on the
     raw physical devices because it allows reading and	writing	in arbitrary
     block sizes.

FILES    [Toc]    [Back]

		    language-specific message file (see	LANG on	environ(5))

SEE ALSO    [Toc]    [Back]

     cp(1), lseek64(2).

DIAGNOSTICS    [Toc]    [Back]

     f<b>+p <b>records in(out)
	  numbers of full and partial blocks read(written)

NOTES    [Toc]    [Back]

     Do	not use	dd to copy files between filesystems having different block

     Using a blocked device to copy a file results in extra nulls being	added
     to	the file to pad	the final block	to the block boundary.

									PPPPaaaaggggeeee 3333
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