# 2.11BSD#431 - /usr/man/cat1/dd.0

    DD(1)		    UNIX Programmer's 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 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 variable length records 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-

    Printed 11/26/99	 April 29, 1985                         1

    DD(1)		    UNIX Programmer's Manual		    DD(1)

         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.

    Printed 11/26/99	 April 29, 1985                         2

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