dd(1)							      General Commands Manual							     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 industry standards and associated tags.

OPTIONS

       None

OPERANDS

       The  option=value operand set may take any of the following forms: Specifies the input file name; standard input is the default.  Specifies
       the output file name; standard output is the default.  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  seper-
       ated by x, specifying the product of the indicated values.

	      All the operands will be processed before any input is read.  Skips number input records before starting copy.  [Tru64 UNIX]  Copies
	      number input files before terminating (makes sense only where input is a magnetic tape or similar device).  [Tru64  UNIX]  Seeks	to
	      the  numberth record from the beginning of input file before copying.  [Tru64 UNIX]  Seeks to the numberth record from the beginning
	      of output file before copying.  Same as seek=number.  Seeks to the numberth record from the beginning of output file before copying.
	      Same  as	oseek=number.	Copies	only number input records.  Specifies one or more of the following conversions: Converts EBCDIC to
	      ASCII.  Converts variable-length records to fixed-length.  Converts ASCII to EBCDIC.  Converts  IBM-EBCDIC  to  ASCII.   Performs  a
	      slightly different map of ASCII to EBCDIC.  Converts fixed-length records to variable-length.  Makes all alphabetic characters lower
	      case.  Makes all alphabetic characters upper case.  Swaps every pair of bytes.  Does not stop processing on an  error.   Pads  every
	      input  record  to ibs.  [Tru64 UNIX]  Creates a sparse output file as described in AdvFS Administration.	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  oper-
	      and.)  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 standard 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 necessarily 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 specified: ascii, unblock, ebcdic, ibm, or block.  For the	first  two
       conversions,  dd  places characters in a conversion buffer of size cbs, converts these characters to ASCII, trims trailing spaces, and adds
       newline characters 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

       [Tru64  UNIX]  To  copy	to  a  raw  disk,  the	disk label must first be zeroed using the disklabel -z command.  For example: disklabel -z
       disk/cdrom17

	      [Tru64 UNIX]  If you do not zero out the disk label, dd fails with the following error message: dd write error: Read-only file  sys-
	      tem  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.  [Tru64 UNIX]  One must specify conv=noerror,sync when copying raw disks with bad sectors	to
	      ensure  dd  stays  synchronized.	 [Tru64  UNIX]	Certain  combinations  of arguments to conv= are permitted.  However, the block or
	      unblock option cannot be combined with ascii, ebcdic, or ibm.  Invalid combinations silently ignore all but the last mutually exclu-
	      sive  keyword.  [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.  [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.  [Tru64 UNIX]  The dd command does not support floppy disk multivolumes, but it does support tape  multivol-
	      umes.  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 tar-
       get 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: The input file was successfully copied.	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

       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.  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: 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  vari-
       ables  contain  an  invalid setting, the utility behaves as if none of the variables had been defined.  If set to a non-empty string value,
       overrides the values of all the other internationalization variables.  Determines the locale for the interpretation of sequences  of  bytes
       of  text data as characters (for example, single-byte as opposed to multibyte characters in arguments).	Determines the locale for the for-
       mat and contents of diagnostic messages written to standard error.  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

																	     dd(1)