DD(1)							      General Commands 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 conversion 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 similar 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 characters are placed  into
       the  conversion	buffer, any specified character mapping is done, trailing blanks trimmed and new-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'  conversion,  while  less
       blessed as a standard, corresponds better to certain IBM print train conventions.  There is no universal 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.

4th Berkeley Distribution					  April 29, 1985							     DD(1)