
DD(1)							    DD(1)


NAME
       dd - convert and copy a file

SYNOPSIS
       dd  [--help]  [--version]  [if=file] [of=file] [ibs=bytes]
       [obs=bytes]    [bs=bytes]    [cbs=bytes]	    [skip=blocks]
       [seek=blocks]  [count=blocks]  [conv={ascii,  ebcdic, ibm,
       block, unblock,	lcase,	ucase,	swab,  noerror,	 notrunc,
       sync}]

DESCRIPTION
       dd  copies a file (from standard input to standard output,
       by default) using specific input	 and  output  blocksizes,
       while optionally performing conversions on it.

       It  reads  the input one block at a time, using the speci-
       fied input block size (the default is 512 bytes).  If  the
       bs=bytes	 option	 was  given, and no conversion other than
       sync, noerror, or notrunc was  specified,  it  writes  the
       amount  of data read (which could be smaller than what was
       requested) in a separate output block. This  output  block
       has  precisely the same length as was read unless the sync
       conversion was specified, in which case the data is padded
       with NULs (or spaces, see below).

       Otherwise,  the	input,	read one block at a time, is pro-
       cessed and the resulting output is collected  and  written
       in  blocks  of  the specified output block size. The final
       output block may be shorter.

       The numeric-valued options below (bytes and blocks) can be
       followed	 by a multiplier: `k'=1024, `b'=512, `w'=2, `c'=1
       (`w' and `c' are GNU extensions; `w' should never be  used
       - it means 2 in System V and 4 in 4.2BSD).  Two or more of
       such numeric expressions can be multiplied by putting  `x'
       in between.

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

       of=file
	      Write  to	 file instead of standard output.  Unless
	      conv=notrunc is given, dd truncates  file	 to  zero
	      bytes (or the size specified with seek=).

       ibs=bytes
	      Read bytes bytes at a time. The default is 512.

       obs=bytes
	      Write bytes bytes at a time. The default is 512.

       bs=bytes
	      Both  read  and  write bytes bytes at a time.  This
	      overrides ibs and obs.   (And  setting  bs  is  not
	      equivalent  with	setting	 both ibs and obs to this
	      same value, at least when no conversion other  than
	      sync,  noerror  and  notrunc is specified, since it
	      stipulates that each input block shall be copied to
	      the  output  as  a single block without aggregating
	      short blocks.)

       cbs=bytes
	      Specify the conversion block  size  for  block  and
	      unblock.

       skip=blocks
	      Skip  blocks  ibs-byte  blocks  in  the  input file
	      before copying.

       seek=blocks
	      Skip blocks obs-byte  blocks  in	the  output  file
	      before copying.

       count=blocks
	      Copy  blocks  ibs-byte  blocks from the input file,
	      instead of everything until the end of the file.

       conv=CONVERSION[,CONVERSION]...
	      Convert the file as  specified  by  the  CONVERSION
	      argument(s).  (No spaces around any comma(s).)

	      Conversions:


	      ascii  Convert EBCDIC to ASCII.

	      ebcdic Convert ASCII to EBCDIC.

	      ibm    Convert ASCII to alternate EBCDIC.

	      block  For  each	line  in  the  input,  output cbs
		     bytes, replacing the input	 newline  with	a
		     space  and padding with spaces as necessary.

	      unblock
		     Replace trailing spaces  in  each	cbs-sized
		     input block with a newline.

	      lcase  Change uppercase letters to lowercase.

	      ucase  Change lowercase letters to uppercase.

	      swab   Swap  every  pair	of  input bytes.  GNU dd,
		     unlike others, works when an odd  number  of
		     bytes  are	 read  -  the last byte is simply
		     copied (since there is nothing  to	 swap  it
		     with).

	      noerror
		     Continue after read errors.

	      notrunc
		     Do not truncate the output file.

	      sync   Pad  every	 input	block to size of ibs with
		     trailing zero bytes.

GNU STANDARD OPTIONS
       --help Print a usage message on standard output	and  exit
	      successfully.

       --version
	      Print  version information on standard output, then
	      exit successfully.

       --     Terminate option list.

ENVIRONMENT
       The variables LANG, LC_ALL, LC_CTYPE and LC_MESSAGES  have
       the usual meaning.

CONFORMING TO
       POSIX 1003.2

NOTES
       This  page  describes  dd  as  found in the fileutils-3.16
       package; other versions may differ slightly. Mail  correc-
       tions and additions to aeb@cwi.nl and aw@mail1.bet1.puv.fi
       and ragnar@lightside.ddns.org .	Report bugs in	the  pro-
       gram to fileutils-bugs@gnu.ai.mit.edu.

GNU fileutils 3.16	   August 1998				3


