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NAME    [Toc]    [Back]

       dd - Converts and copies a file

SYNOPSIS    [Toc]    [Back]

       dd [option=value...]

STANDARDS    [Toc]    [Back]

       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    [Toc]    [Back]


OPERANDS    [Toc]    [Back]

       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  separated  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 Nth record from  the  beginning
              of  input file before copying.  [Tru64 UNIX]  Seeks
              to the Nth record from the beginning of output file
              before copying.  Same as seek=number.  Seeks to the
              Nth 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 operand.)   Allows
              several comma-separated conversions.

DESCRIPTION    [Toc]    [Back]

       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

       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    [Toc]    [Back]

       [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  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  exclusive   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
              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    [Toc]    [Back]
       [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    [Toc]    [Back]

       The following exit values are returned: The input file was
       successfully copied.  An error occurred

DIAGNOSTICS    [Toc]    [Back]

       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    [Toc]    [Back]

       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.


       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 variables 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 format
       and contents of diagnostic messages  written  to  standard
       error.   Determines the location of message catalogues for
       the processing of LC_MESSAGES.

SEE ALSO    [Toc]    [Back]

       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

[ Back ]
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