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



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=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 conver-
                    sion is specified, it is particularly effi-
                    cient since no copy need be done
     cbs=n          conversion buffer size
     skip=n         skip n input records before starting copy
     files=n        copy n input files before terminating (makes
                    sense only where input is a magtape or simi-
                    lar device).
     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
          block     convert newline terminated ascii strings to
                    fixed length
          unblock   convert fixed length records to variable
                    length
          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; a pair of numbers may be
     separated by x to indicate a product.

     Cbs is used only if ascii, unblock, ebcdic, ibm, or block
     conversion is specified.  In the first two cases, cbs char-
     acters are placed into the conversion buffer, any specified
     character mapping is done, trailing blanks trimmed and new-



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



     line added before sending the line to the output.  In the
     latter three cases, characters are read into the conversion
     buffer, 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(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' conver-
     sion, while less blessed as a standard, corresponds better
     to certain IBM print train conventions.  There is no univer-
     sal solution.
     One must specify ``conv=noerror,sync'' when copying raw
     disks with bad sectors to insure dd stays synchronized.

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

















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