DD(I) 5/15/74 DD(I)





DD(I)                        5/15/74                        DD(I)







NAME

     dd - convert and copy a file



SYNOPSIS

     dd [option=value] ...



DESCRIPTION

     Dd copies the specified input file to the  specified  output

     with  possible  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=            input block size (default 512)

     obs=            output block size (default 512)

     bs=             set  both  input  and  output  block   size,

                    superseding   ibs   and   obs;  also,  if  no

                    conversion is specified, it  is  particularly

                    efficient since no copy need be done

     cbs=n           conversion buffer size

     skip=n          skip n input records before starting copy

     count=n         copy only n input records

     conv=ascii      convert EBCDIC to ASCII

          ebcdic     convert 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 respectively.  Also 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, converted 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.







SEE ALSO

     cp (I)



BUGS

     The ASCII/EBCDIC conversion tables are taken  from  the  256

     character  standard  in the CACM Nov, 1968.  It is not clear

     how this relates to real life.



     Newlines are inserted only on conversion to  ASCII;  padding

     is  done  only  on  conversion  to  EBCDIC.  There should be

     separate options.
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