SYNOPSIS

       dd [option=value] ...

DESCRIPTION

       Dd  copies the specified input file to the specified output with possi-
       ble 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 par-
                      ticularly efficient since no copy need be done
       cbs=n          conversion buffer size
       skip=n         skip n input records before starting copy
       iseek=n        seek n input records before starting copy
       files=n        copy n files from (tape) input
       seek=n         seek n records from  beginning  of  output  file  before
                      copying
       oseek=n        same as seek
       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 input lines to blocks
            unblock   convert blocked input to lines
            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
            notrunc   do not truncate the output file
            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 respec-
       tively;  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 bytes are placed into the con-
       version buffer, converted to ASCII, and  trailing  blanks  trimmed  and
       new-line  added  before  sending the line to the output.  In the latter
       three cases, ASCII characters (bytes)  are  read  into  the  conversion
       buffer,  converted  to  EBCDIC,  and  blanks added to make up an output
       record of size cbs.

       Two  additional  values  for  the  `conv'  option,  `conv=idirect'  and
       `conv=odirect', are available as extensions.  They enable direct i/o on

       LC_CTYPE
              Determines  the  mapping of bytes to characters for `conv=lcase'
              and `conv=ucase'.

EXAMPLES

       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.

       To skip over a file before copying from magnetic tape do

              (dd of=/dev/null; dd of=x) </dev/rmt0

SEE ALSO

       cp(1), tr(1), locale(7)

DIAGNOSTICS

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

NOTES

       The  ASCII/EBCDIC conversion tables are taken from a proposed BTL stan-
       dard April 16, 1979.  The `ibm' conversion, while  less  blessed  as  a
       standard,  corresponds  better  to certain IBM print train conventions.
       There is no universal solution.

       When reading from pipes, FIFOs, character devices (e.g. terminals),  or
       network  sockets,  partial  input  records  can  occur at any time even
       before the end of the data stream is reached.  For the `count'  option,
       these  are  handled  exactly  like  full records.  Using dd to retrieve
       exactly count*ibs bytes from such files does thus  not  generally  work
       unless `ibs=1'.



Heirloom Toolchest                  1/14/05                              DD(1)