DD(1)                                BSD                                 DD(1)



NAME
     dd - convert and copy a file

SYNOPSIS
     dd [ option=value ] ...

DESCRIPTION
     The dd command copies the specified input file to the specified output
     with possible conversions.  It uses the standard input and output by
     default.  You can specify the input and output block size to take
     advantage of raw physical I/O.  After completion, dd reports the number
     of whole and partial input and output blocks.

OPTIONS
     if=file         Input filename; standard input is the default.
     of=file         Output filename; standard output is the default.
     ibs=n           Input block size n bytes; 512 is the default.
     obs=n           Output block size; 512 is the default.
     bs=n            Set both input and output block size, superseding ibs and
                     obs.  If you do not specify conversion, this is
                     particularly efficient since no copy is required.
     cbs=n           Conversion buffer size; used only if ascii, unblock,
                     ebcdic, ibm, or block conversion is specified.  In the
                     first two cases, cbs characters are placed in the
                     conversion buffer, any specified character mapping is
                     done, trailing blanks are trimmed, and a newline is added
                     before sending the line to the output.  In the latter
                     three cases, characters are read into the conversion
                     buffer, and blanks are added to make up an output record
                     of size cbs.
     skip=n          Skip n input records before starting copy.
     files=n         Copy n input files before terminating  This option makes
                     sense only where input is a magtape or similar device.
     seek=n          Seek n records from the beginning of the output file
                     before copying.
     count=n         Copy only n input records.
     conv=ascii      Convert EBCDIC to ASCII.
          ebcdic     Convert ASCII to EBCDIC.
          ibm        A slightly different map of ASCII to EBCDIC.
          block      Convert variable-length records to fixed-length records.
          unblock    Convert fixed-length records to variable-length records.
          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.
          ... , ...  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.  A pair of numbers can be separated by x to indicate a
     product.

NOTES
     Certain combinations of arguments to conv= are permitted.  However, you
     cannot combine the block or unblock options with ascii, ebcdic or ibm.
     Invalid combinations silently ignore all but the last mutually-exclusive
     keyword.

     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.

EXAMPLE
     To read an EBCDIC tape, blocked ten 80-byte EBCDIC card images per
     record, into the ASCII file x, type the following:


          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.

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

BUGS
     You must specify conv=noerror,sync when copying raw disks with bad
     sectors to ensure that dd stays synchronized.

     Domain/OS BSD does not support some raw I/O devices typically used with
     dd.

SEE ALSO
     cp(1), tr(1)