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DD(1)                       General Commands Manual                      DD(1)



NAME
       dd - convert and copy a file

SYNOPSIS
       dd [option=value] ...

DESCRIPTION
       Dd  copies the specified input file to the specified output with possi-
       ble conversions.  The standard input and output are  used  by  default.
       The  input  and output block size may be specified to take advantage of
       raw physical I/O.

       option         values
       if=            input file name; standard input is default
       of=            output file name; standard output is default
       ibs=n          input block size n bytes (default 512)
       obs=n          output block size (default 512)
       bs=n           set both input and output block  size,  superseding  ibs
                      and obs; also, if no conversion is specified, it is par-
                      ticularly efficient since no copy need be done
       cbs=n          conversion buffer size
       skip=n         skip n input records before starting copy
       files=n        copy n files from (tape) input
       seek=n         seek n records from  beginning  of  output  file  before
                      copying
       count=n        copy only n input records
       conv=ascii     convert EBCDIC to ASCII
            ebcdic    convert ASCII to EBCDIC
            ibm       slightly different map of ASCII to EBCDIC
            lcase     map alphabetics to lower case
            ucase     map alphabetics to upper case
            swab      swap every pair of bytes
            noerror   do not stop processing on an error
            sync      pad every input record to ibs
            ... , ... several comma-separated conversions

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

       Cbs  is  used  only if ascii or ebcdic conversion is specified.  In the
       former case cbs characters are placed into the conversion buffer,  con-
       verted  to ASCII, and trailing blanks trimmed and new-line added before
       sending the line to the output.  In the latter  case  ASCII  characters
       are  read  into  the conversion buffer, converted to EBCDIC, and blanks
       added to make up an output record of size cbs.

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

       For  example,  to  read  an EBCDIC tape blocked ten 80-byte EBCDIC card
       images per record into the ASCII file x:

              dd if=/dev/rmt0 of=x ibs=800 cbs=80 conv=ascii,lcase

       Note the use of raw magtape.  Dd is especially suited to I/O on the raw
       physical  devices  because  it  allows reading and writing in arbitrary
       record sizes.

       To  skip  over  a  file  before  copying  from  magnetic  tape  do  (dd
       of=/dev/null; dd of=x) </dev/rmt0

SEE ALSO
       cp(1), tr(1)

DIAGNOSTICS
       f+p records in(out): numbers of full and partial records read(written)

BUGS
       The  ASCII/EBCDIC  conversion  tables  are taken from the 256 character
       standard in the CACM Nov,  1968.   The  `ibm'  conversion,  while  less
       blessed  as  a  standard, corresponds better to certain IBM print train
       conventions.  There is no universal solution.

       Newlines are inserted only on conversion to ASCII; padding is done only
       on conversion to EBCDIC.  These should be separate options.



                                                                         DD(1)