dd(1)                                                       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 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=file         input filename; standard input is default
          of=file         output filename; 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, su-
                          perseding ibs and obs; also, if no conver-
                          sion is specified, it is particularly effi-
                          cient since no incore copy needs to be gen-
                          erated
          cbs=n           conversion buffer size
          skip=n          skip n input blocks before starting copy
          seek=n          seek n blocks from beginning of output file
                          before copying; dd creates the specified
                          output file (see creat(2)), which insures
                          that the length of the file will be zero for
                          regular files; seeking n blocks from the be-
                          ginning of the output file will fill the
                          skipped area with zeros (nulls)
          count=n         copy only n input blocks
          conv=ascii      convert EBCDIC to ASCII
               ebcdic     convert ASCII to EBCDIC
               ibm        slightly different map of ASCII to EBCDIC
               lcase      map alphabetics to lowercase
               ucase      map alphabetics to uppercase
               swab       swap every pair of bytes
               noerror    do not stop processing on an error
               sync       pad every input block to ibs
               type,type  several comma-separated conversions, where
                          type is one of the conversions listed for
                          conv
          multi=in        input file is multivolume
                out  output file is multivolume
                in,out
                     both the input file and output file are multivo-
                     lume

          Where sizes are specified, a number of bytes is expected.  A
          number may end with k, b, or w to specify multiplication by



     April, 1990                                                     1

     dd(1)                                                       dd(1)



          1024, 512, or 2, respectively; a pair of numbers may be
          separated by x to indicate a product.

          cbs is used only if ascii, ebcdic, or ibm conversion is
          specified.  In the first case, cbs characters are placed
          into the conversion buffer, converted to ASCII, and trailing
          blanks are trimmed and a newline added before sending the
          line to the output.  In the next two cases, ASCII characters
          are read into the conversion buffer, converted to EBCDIC (or
          the IBM version of EBCDIC), and blanks are added to make up
          an output block of size cbs.

          If multivolume input (output) is specified, a prompt is
          given at end-of-file to allow another volume to be mounted.

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

     EXAMPLES
          dd if=/dev/rmt/0m of=x ibs=800 cbs=80 conv=ascii,lcase

          will read an EBCDIC tape blocked at ten 80-byte EBCDIC card
          images per block into the ASCII file x.

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

     FILES
          /bin/dd

     SEE ALSO
          cp(1), cpio(1), tar(1), tr(1).

     DIAGNOSTICS
             f+p blocks in(out)

          are numbers of full and partial blocks read (written).

     BUGS
          The ASCII/EBCDIC conversion tables are taken from the 256-
          character standard in the CACM, November, 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.

          When using dd to transfer data over an Ethernet connection,
          you should specify a block size of 1 kilobyte.



     2                                                     April, 1990