dd(1)                                                       dd(1)



NAME
     dd - converts and copies a file

SYNOPSIS
     dd [bs=n] [cbs=n] [conv=ascii] [conv=ebcdic] [conv=ibm]
     [conv=lcase] [conv=noerror] [conv=swab] [conv=sync]
     [conv=type,type] [conv=ucase] [count=n] [ibs=n] [if=file]
     [multi=in] [multi=in,out] [multi=out] [of=file] [obs=n]
     [seek=n] [skip=n]

ARGUMENTS
     bs=n Sets both input and output block size, superseding ibs
          and obs; also, if no conversion is specified, it is
          particularly efficient since no incore copy needs to be
          generated

     cbs=n
          Specifies the conversion buffer size.  Replaces n with
          the size of the buffer.

     conv=ascii
          Converts EBCDIC text to ASCII text.

     conv=ebcdic
          Converts ASCII text to EBCDIC text.

     conv=ibm
          Specifies a slightly different map of ASCII to EBCDIC.

     conv=lcase
          Maps alphabetics to lowercase.

     conv=noerror
          Does not stop processing when an error occurs.

     conv=swab
          Swaps every pair of bytes.

     conv=sync
          Pads every input block to ibs.

     conv=type,type
          Specifies several comma-separated conversions, where
          type is one of the conversions listed for conv.

     conv=ucase
          Maps alphabetics to uppercase.

     count=n
          Copies only n input blocks.

     ibs=n



January 1992                                                    1

dd(1)                                                       dd(1)



          Inputs the block size, n bytes (the default 512)

     if=file
          Inputs the file.  The standard input is default.

     multi=in
          Indicates that the input file is multivolume.

     multi=in,out
          Indicates that both the input file and the output file
          are multivolume.

     multi=out
          Indicates that the output file is multivolume.

     of=file
          Outputs the file.  The standard output is default.

     obs=n
          Outputs the block size n.  The default 512.

     seek=n
          Seeks n blocks from beginning of output file before
          copying.  The dd command creates the specified output
          file (see creat(2)), which insures that the length of
          the file will be zero for regular files; seeking n
          blocks from the beginning of the output file will fill
          the skipped area with zeros (nulls)

     skip=n
          Skips n input blocks before starting to copy.

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.

     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.

     The cbs option is used only if ascii, ebcdic, or ibm
     conversion is specified.  In the first case, cbs characters
     are placed into the conversion buffer, converted to ASCII,
     and trailing blanks are trimmed and a newline added before
     sending the line to the output.  In the next two cases,
     ASCII characters are read into the conversion buffer,
     converted to EBCDIC (or the IBM version of EBCDIC), and
     blanks are added to make up an output block of size cbs.




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dd(1)                                                       dd(1)



     If multivolume input (output) is specified, a prompt is
     given at end-of-file to allow another volume to be mounted.

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

EXAMPLES
     The command:

        dd if=/dev/rmt/0m of=x ibs=800 cbs=80 conv=ascii,lcase

     will read an EBCDIC tape blocked at ten 80-byte EBCDIC card
     images per block into the ASCII file x.

     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.

LIMITATIONS
     The ASCII/EBCDIC conversion tables are taken from the 256-
     character standard in the CACM, November, 1968.  The ibm
     conversion, while less blessed as a standard, corresponds
     better to certain IBM print-train conventions.  There is no
     universal solution.

     Newlines are inserted only on conversion to ASCII; padding
     is done only on conversion to EBCDIC.  These should be
     separate options.

     When using dd to transfer data over an Ethernet connection,
     you should specify a block size of 1 kilobyte.

STATUS MESSAGES AND VALUES
     The output:

        f+p blocks in(out)

     contains numbers of full and partial blocks read (written).

FILES
     /bin/dd
          Executable file

SEE ALSO
     cp(1), cpio(1), tar(1), tr(1)










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