DD(1)               RISC/os Reference 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 possible conversions.  The standard input and output
     are used by default.  The input and output block sizes may
     be specified to take advantage of raw physical I/O.

     option          values
     if=file         input file name; standard input is default
     of=file         output file name; standard output is default
     ibs=n           input block size n bytes (default 512)
     obs=n           output block size n bytes (default 512)
     bs=n            set both input and output block size,
                     superseding ibs and obs; also, if no conver-
                     sion is specified, preserve the input block
                     size instead of packing short blocks into
                     the output buffer (this is particularly
                     efficient since no in-core copy need be
                     done)
     cbs=n           conversion buffer size (logical record
                     length)
     files=n         copy and concatenate n input files before
                     terminating (makes sense only where input is
                     a magnetic tape or similar device)
     skip=n          skip n input blocks before starting copy
                     (appropriate for magnetic tape, where iseek
                     is undefined)
     iseek=n         seek n blocks from beginning of input file
                     before copying (appropriate for disk files,
                     where skip can be incredibly slow)
     oseek=n         seek n blocks from beginning of output file
                     before copying
     seek=n          identical to oseek, retained for backward
                     compatibility
     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
          block      convert new-line terminated ASCII records to
                     fixed length
          unblock    convert fixed length ASCII records to new-
                     line terminated records
          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 (limit of
                     5 consecutive errors)



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DD(1)               RISC/os Reference Manual                DD(1)



          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 may be
     separated by x to indicate multiplication.

     cbs is used only if ascii, unblock, ebcdic, ibm, or block
     conversion is specified.  In the first two cases, cbs char-
     acters are copied into the conversion buffer, any specified
     character mapping is done, trailing blanks are trimmed and a
     new-line is added before sending the line to the output.  In
     the latter three cases, characters are read into the conver-
     sion buffer and blanks are added to make up an output record
     of size cbs.  If cbs is unspecified or zero, the ascii,
     ebcdic, and ibm options convert the character set without
     changing the block structure of the input file; the unblock
     and block options become a simple file copy.

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

EXAMPLE
     This command will read an EBCDIC tape blocked ten 80-byte
     EBCDIC card images per tape block into the ASCII file x:

     dd  if=/dev/rmt/0h  of=x  ibs=800  obs=8k  cbs=80
     conv=ascii,lcase

     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.

SEE ALSO
     cp(1)

NOTES
     Do not use dd to copy files between filesystems having dif-
     ferent block sizes.

     Using a  blocked device to copy a file will result in extra
     nulls being added to the file to pad the final block to the
     block boundary.

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







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