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DD(1)			  BSD General Commands Manual			 DD(1)

NAME
     dd	-- convert and copy a file

SYNOPSIS
     dd	[operands ...]

DESCRIPTION
     The dd utility copies the standard	input to the standard output.  Input
     data is read and written in 512-byte blocks.  If input reads are short,
     input from	multiple reads are aggregated to form the output block.	 When
     finished, dd displays the number of complete and partial input and	output
     blocks and	truncated input	records	to the standard	error output.

     The following operands are	available:

     bs=n     Set both input and output	block size, superseding	the ibs	and
	      obs operands.  If	no conversion values other than	noerror,
	      notrunc or sync are specified, then each input block is copied
	      to the output as a single	block without any aggregation of short
	      blocks.

     cbs=n    Set the conversion record	size to	n bytes.  The conversion
	      record size is required by the record oriented conversion	val-
	      ues.

     count=n  Copy only	n input	blocks.

     files=n  Copy n input files before	terminating.  This operand is only ap-
	      plicable when the	input device is	a tape.

     ibs=n    Set the input block size to n bytes instead of the default 512.

     if=file  Read input from file instead of the standard input.

     iseek=n  Seek on the input	file n blocks.	This is	synonymous with
	      skip=n.

     msgfmt=fmt
	      Specify the message format fmt to	be used	when writing informa-
	      tion to standard output.	Possible values	are:
		    quiet  turns off information summary report	except for er-
			   rors	and progress.
		    posix  default information summary report as specified by
			   POSIX.
		    human  default information summary report extended with
			   human-readable values.

	      When fmt does not	correspond to any value	given above, it	con-
	      tains a string that will be used as format specifier for the in-
	      formation	summary	output.	 Each conversion specification is in-
	      troduced by the character	%.  The	following ones are available:
		    b	total number of	bytes transferred
		    B	total number of	bytes transferred in
			humanize_number(3) format
		    e	speed transfer
		    E	speed transfer in humanize_number(3) format
		    i	number of partial input	block(s)
		    I	number of full input block(s)
		    o	number of partial output block(s)
		    O	number of full output block(s)
		    s	time elapsed since the beginning in "seconds.ms" for-
			mat
		    p	number of sparse output	blocks
		    t	number of truncated blocks
		    w	number of odd-length swab blocks
		    P	singular/plural	of "block" depending on	number of
			sparse blocks
		    T	singular/plural	of "block" depending on	number of
			truncated blocks
		    W	singular/plural	of "block" depending on	number of swab
			blocks

     obs=n    Set the output block size	to n bytes instead of the default 512.

     of=file  Write output to file instead of the standard output.  Any	regu-
	      lar output file is truncated unless the notrunc conversion value
	      is specified.  If	an initial portion of the output file is
	      skipped (see the seek operand) the output	file is	truncated at
	      that point.

     oseek=n  Seek on the output file n	blocks.	 This is synonymous with
	      seek=n.

     seek=n   Seek n blocks from the beginning of the output before copying.
	      On non-tape devices, a lseek(2) operation	is used.  Otherwise,
	      existing blocks are read and the data discarded.	If the user
	      does not have read permission for	the tape, it is	positioned us-
	      ing the tape ioctl(2) function calls.  If	the seek operation is
	      past the end of file, space from the current end of file to the
	      specified	offset is filled with blocks of	NUL bytes.

     skip=n   Skip n blocks from the beginning of the input before copying.
	      On input which supports seeks, a lseek(2)	operation is used.
	      Otherwise, input data is read and	discarded.  For	pipes, the
	      correct number of	bytes is read.	For all	other devices, the
	      correct number of	blocks is read without distinguishing between
	      a	partial	or complete block being	read.

     progress=n
	      Switch on	display	of progress if n is set	to any non-zero	value.
	      This will	cause a	"." to be printed (to the standard error out-
	      put) for every n full or partial blocks written to the output
	      file.

     conv=value[,value...]
	      Where value is one of the	symbols	from the following list.

	      ascii, oldascii
		       The same	as the unblock value except that characters
		       are translated from EBCDIC to ASCII before the records
		       are converted.  (These values imply unblock if the op-
		       erand cbs is also specified.)  There are	two conversion
		       maps for	ASCII.	The value ascii	specifies the recom-
		       mended one which	is compatible with AT&T	System V UNIX.
		       The value oldascii specifies the	one used in historic
		       AT&T and	pre- 4.3BSD-Reno systems.

	      block    Treats the input	as a sequence of newline or end-of-
		       file terminated variable	length records independent of
		       input and output	block boundaries.  Any trailing	new-
		       line character is discarded.  Each input	record is con-
		       verted to a fixed length	output record where the	length
		       is specified by the cbs operand.	 Input records shorter
		       than the	conversion record size are padded with spaces.
		       Input records longer than the conversion	record size
		       are truncated.  The number of truncated input records,
		       if any, are reported to the standard error output at
		       the completion of the copy.

	      ebcdic, ibm, oldebcdic, oldibm
		       The same	as the block value except that characters are
		       translated from ASCII to	EBCDIC after the records are
		       converted.  (These values imply block if	the operand
		       cbs is also specified.)	There are four conversion maps
		       for EBCDIC.  The	value ebcdic specifies the recommended
		       one which is compatible with AT&T System	V UNIX.	 The
		       value ibm is a slightly different mapping, which	is
		       compatible with the AT&T	System V UNIX ibm value.  The
		       values oldebcdic	and oldibm are maps used in historic
		       AT&T and	pre 4.3BSD-Reno	systems.

	      lcase    Transform uppercase characters into lowercase charac-
		       ters.

	      noerror  Do not stop processing on an input error.  When an in-
		       put error occurs, a diagnostic message followed by the
		       current input and output	block counts will be written
		       to the standard error output in the same	format as the
		       standard	completion message.  If	the sync conversion is
		       also specified, any missing input data will be replaced
		       with NUL	bytes (or with spaces if a block oriented con-
		       version value was specified) and	processed as a normal
		       input buffer.  If the sync conversion is	not specified,
		       the input block is omitted from the output.  On input
		       files which are not tapes or pipes, the file offset
		       will be positioned past the block in which the error
		       occurred	using lseek(2).

	      notrunc  Do not truncate the output file.	 This will preserve
		       any blocks in the output	file not explicitly written by
		       dd.  The	notrunc	value is not supported for tapes.

	      osync    Pad the final output block to the full output block
		       size.  If the input file	is not a multiple of the out-
		       put block size after conversion,	this conversion	forces
		       the final output	block to be the	same size as preceding
		       blocks for use on devices that require regularly	sized
		       blocks to be written.  This option is incompatible with
		       use of the bs=n block size specification.

	      sparse   If one or more non-final	output blocks would consist
		       solely of NUL bytes, try	to seek	the output file	by the
		       required	space instead of filling them with NULs.  This
		       results in a sparse file	on some	file systems.

	      swab     Swap every pair of input	bytes.	If an input buffer has
		       an odd number of	bytes, the last	byte will be ignored
		       during swapping.

	      sync     Pad every input block to	the input buffer size.	Spaces
		       are used	for pad	bytes if a block oriented conversion
		       value is	specified, otherwise NUL bytes are used.

	      ucase    Transform lowercase characters into uppercase charac-
		       ters.

	      unblock  Treats the input	as a sequence of fixed length records
		       independent of input and	output block boundaries.  The
		       length of the input records is specified	by the cbs op-
		       erand.  Any trailing space characters are discarded and
		       a newline character is appended.

     Where sizes are specified,	a decimal number of bytes is expected.	Two or
     more numbers may be separated by an "x" to	indicate a product.  Each num-
     ber may have one of the following optional	suffixes:
	   b	Block; multiply	by 512
	   k	Kibi; multiply by 1024 (1 KiB)
	   m	Mebi; multiply by 1048576 (1 MiB)
	   g	Gibi; multiply by 1073741824 (1	GiB)
	   t	Tebi; multiply by 1099511627776	(1 TiB)
	   w	Word; multiply by the number of	bytes in an integer

     When finished, dd displays	the number of complete and partial input and
     output blocks, truncated input records and	odd-length byte-swapping
     blocks to the standard error output.  A partial input block is one	where
     less than the input block size was	read.  A partial output	block is one
     where less	than the output	block size was written.	 Partial output	blocks
     to	tape devices are considered fatal errors.  Otherwise, the rest of the
     block will	be written.  Partial output blocks to character	devices	will
     produce a warning message.	 A truncated input block is one	where a	vari-
     able length record	oriented conversion value was specified	and the	input
     line was too long to fit in the conversion	record or was not newline ter-
     minated.

     Normally, data resulting from input or conversion or both are aggregated
     into output blocks	of the specified size.	After the end of input is
     reached, any remaining output is written as a block.  This	means that the
     final output block	may be shorter than the	output block size.

     If	dd receives a SIGINFO signal (see the status argument for stty(1)),
     the current input and output block	counts will be written to the standard
     error output in the same format as	the standard completion	message.  If
     dd	receives a SIGINT signal, the current input and	output block counts
     will be written to	the standard error output in the same format as	the
     standard completion message and dd	will exit.

EXIT STATUS
     The dd utility exits 0 on success and >0 if an error occurred.

EXAMPLES
     To	print summary information in human-readable form:

	   dd if=/dev/zero of=/dev/null	count=1	msgfmt=human

     To	customize the information summary output and print it through
     unvis(3):

	   dd if=/dev/zero of=/dev/null	count=1	\
		msgfmt='speed:%E, in %s	seconds\n' 2>&1	| unvis

SEE ALSO
     cp(1), mt(1), tr(1)

STANDARDS
     The dd utility is expected	to be a	superset of the	IEEE Std 1003.2
     ("POSIX.2") standard.  The	files and msgfmt operands and the ascii,
     ebcdic, ibm, oldascii, oldebcdic and oldibm values	are extensions to the
     POSIX standard.

BSD			       November	6, 2011				   BSD

NAME | SYNOPSIS | DESCRIPTION | EXIT STATUS | EXAMPLES | SEE ALSO | STANDARDS

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