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dd(1)									dd(1)



NAME

  dd - Converts	and copies a file

SYNOPSIS

  dd [option=value...]

STANDARDS

  Interfaces documented	on this	reference page conform to industry standards
  as follows:

  dd:  XCU5.0, SVID 4

  Refer	to the standards(5) reference page for more information	about indus-
  try standards	and associated tags.

OPTIONS

  None

OPERANDS

  The option=value operand set may take	any of the following forms:

  if=input_file
      Specifies	the input file name; standard input is the default.

  of=output_file
      Specifies	the output file	name; standard output is the default.

  ibs=,	obs=, bs= and cbs=
      For the above operands, the application must supply an expression
      specifying a size	in bytes. The expression, expr can be:

	+  a positive decimal number

	+  a positive decimal number followed by k specifying mutiplication
	   by 1024

	+  a positive decimal number followed by b specifying multiplication
	   by 512

	+  two or more positive	decimal	numbers	with or	without	k or b
	   separated by	x, specifying the product of the indicated values.

      All the operands will be processed before	any input is read.

  skip=number
      Skips number input records before	starting copy.

  files=number
      [Tru64 UNIX]  Copies number input	files before terminating (makes	sense
      only where input is a magnetic tape or similar device).

  iseek=number
      [Tru64 UNIX]  Seeks to the Nth record from the beginning of input	file
      before copying.

  oseek=number
      [Tru64 UNIX]  Seeks to the Nth record from the beginning of output file
      before copying.  Same as seek=number.

  seek=number
      Seeks to the Nth record from the beginning of output file	before copy-
      ing.  Same as oseek=number.

  count=number
      Copies only number input records.

  conv=specification[,specification ...]
      Specifies	one or more of the following conversions:

      ascii
	  Converts EBCDIC to ASCII.

      block
	  Converts variable-length records to fixed-length.

      ebcdic
	  Converts ASCII to EBCDIC.

      iascii
	  Converts IBM-EBCDIC to ASCII.

      ibm Performs a slightly different	map of ASCII to	EBCDIC.

      unblock
	  Converts fixed-length	records	to variable-length.

      lcase
	  Makes	all alphabetic characters lower	case.

      ucase
	  Makes	all alphabetic characters upper	case.

      swab
	  Swaps	every pair of bytes.

      noerror
	  Does not stop	processing on an error.

      sync
	  Pads every input record to ibs.

      sparse
	  [Tru64 UNIX]	Creates	a sparse output	file as	described in AdvFS
	  Administration.

      notrunc
	  Do not truncate the output file. Preserve blocks in the output file
	  not explicitly written by this invocation of the dd utility. (See
	  the of=output_file operand.)

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



DESCRIPTION

  The dd command reads the specified input file	or standard input, does	the
  specified conversions, and copies it to the specified	output file or stan-
  dard output.	The input and output block size	may be specified to take
  advantage of raw physical I/O.  The terms block and record refer to the
  quantity of data read	or written by dd in one	operation and are not neces-
  sarily the same size as a disk block.

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

  The cbs specification	is used	if one of the following	conversions is speci-
  fied:	ascii, unblock,	ebcdic,	ibm, or	block.	For the	first two conver-
  sions, dd places characters in a conversion buffer of	size cbs, converts
  these	characters to ASCII, trims trailing spaces, and	adds newline charac-
  ters before sending data to the specified output.  For the latter three
  cases, dd places ASCII characters in the conversion buffer, converts these
  characters to	EBCDIC,	and adds trailing spaces to create an output record
  of size cbs.

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

NOTES

   1.  [Tru64 UNIX]  To	copy to	a raw disk, the	disk label must	first be
       zeroed using the	disklabel -z command.  For example:
	    disklabel -z /dev/disk/dsk1

       [Tru64 UNIX]  If	you do not zero	out the	disk label, dd fails with the
       following error message:
	    dd write error: Read-only file system

   2.  The ASCII/EBCDIC	conversion tables are taken from the 256 character
       standard	in the CACM November, 1968. There is no	universal standard
       for EBCDIC/ASCII	translation.

   3.  [Tru64 UNIX]  One must specify conv=noerror,sync	when copying raw
       disks with bad sectors to ensure	dd stays synchronized.

   4.  [Tru64 UNIX]  Certain combinations of arguments to conv=	are permit-
       ted.  However, the block	or unblock option cannot be combined with
       ascii, ebcdic, or ibm.  Invalid combinations silently ignore all	but
       the last	mutually exclusive keyword.

   5.  [Tru64 UNIX]  If	you need to use	dd to copy to a	streaming tape and
       the data	is an odd length (not a	multiple of 512	bytes),	you must use
       the conv=sync flag to fill the last record.  Streaming tape devices
       permit only multiples of	512 bytes.

   6.  [Tru64 UNIX]  If	option bs is used (or bs is equal to obs) and no
       conversion is specified,	then dd	is particularly	efficient since	less
       memory copies are done.

   7.  [Tru64 UNIX]  The dd command does not support floppy disk multivo-
       lumes, but it does support tape multivolumes.  This means that when
       ENOSPC is returned while	reading	or writing a tape, dd will prompt the
       user for	a new tape.

       [Tru64 UNIX]  In	order to make use of tape multivolumes,	the files
       option must be used.



  Security Note


  [Tru64 UNIX]	Any file system	archive	that contains ACLs (access control
  lists) that was created using	dd is not exportable unless the	target system
  has the exact	same password and group	files.	If there is a mismatch,
  incorrect access may be granted to a file or directory.

EXIT STATUS

  The following	exit values are	returned:

  0   The input	file was successfully copied.

  >>0  An error occurred

DIAGNOSTICS

  This message specifies the number of full and	partial	records	both read and
  written:

       f+p records in
       f+p records out

  The number of	full records read or written (f) refers	to the blocks of data
  of size ibs or obs.  The number of partial records read or written (p)
  refers to the	blocks of data smaller than ibs	or obs.

EXAMPLES

   1.  To read an EBCDIC tape blocked ten 80-byte EBCDIC card images per
       record into the ASCII file x, enter:
	    dd if=/dev/tape/tape0_d0 of=x ibs=800 cbs=80 conv=ascii,lcase

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

   2.  To convert an ASCII text	file to	EBCDIC,	enter:
	    dd if=text.ascii of=text.ebcdic conv=ebcdic

       This converts text.ascii	to EBCDIC representation, storing this in
       text.ebcdic.

ENVIRONMENT VARIABLES

  The following	environment variables affect the execution of dd:

  LANG
      Provides a default value for the internationalization variables that
      are unset	or null. If LANG is unset or null, the corresponding value
      from the default locale is used. If any of the internationalization
      variables	contain	an invalid setting, the	utility	behaves	as if none of
      the variables had	been defined.

  LC_ALL
      If set to	a non-empty string value, overrides the	values of all the
      other internationalization variables.

  LC_CTYPE
      Determines the locale for	the interpretation of sequences	of bytes of
      text data	as characters (for example, single-byte	as opposed to multi-
      byte characters in arguments).

  LC_MESSAGES
      Determines the locale for	the format and contents	of diagnostic mes-
      sages written to standard	error.

  NLSPATH
      Determines the location of message catalogues for	the processing of
      LC_MESSAGES.

SEE ALSO

  Commands:  cp(1), cpio(1), sed(1), tar(1), tr(1), trbsd(1)

  Functions:  lseek(2)

  Routines:  fseek(3)

  Files:  ascii(5)

  Standards:  standards(5)

  Command and Shell User's Guide

  AdvFS	Administration