dd(C)                           19 June 1992                           dd(C)


 Name

    dd - convert and copy a file

 Syntax

    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.

    if=file              Input filename; standard input is default

    of=file              Output filename; standard output is default

    ibs=n                Input block size is n bytes (default is BSIZE block
                         size)

    obs=n                Output block size (default is BSIZE block size)

    bs=n                 Sets both input and output block size, superseding
                         ibs and obs.  If no conversion is specified, it is
                         particularly efficient since no in-core copy needs
                         to be done

    cbs=n                Conversion buffer size

    skip=n               Skips n input records before starting copy. (The
                         records are read but not output.)

    seek=n               Seeks n records from beginning of output file before
                         copying

    iseek=n              Same as skip, but seeks over the records (that is,
                         uses iseek(S))

    oseek=n              As for seek.

    files=n              Specify the number of input files to concatenate.
                         This option effectively causes a sequence of n EOFs
                         to be ignored.  (It is generally only useful for
                         tape.)

    conv=block           Convert ASCII to unblocked ASCII.

    conv=unblock         Convert unblocked ASCII to ASCII.

    count=n              Copies only n input records

    conv=ascii           Converts EBCDIC to ASCII

    conv=ebcdic          Converts ASCII to EBCDIC

    conv=ibm             Slightly different map of ASCII to EBCDIC

    conv=lcase           Maps alphabetic characters to lowercase

    conv=ucase           Maps alphabetic characters to uppercase

    conv=swab            Swaps every pair of bytes

    conv=noerror         Does not stop processing on an error

    conv=sync            Pads every input record to ibs

    conv=... , ...       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, ebcdic, or ibm conversion is specified.  In
    the former case, cbs characters are placed into the conversion buffer,
    converted to ASCII, and trailing blanks trimmed and newline added before
    sending the line to the output.  In the latter two cases, ASCII charac-
    ters are read into the conversion buffer, converted to EBCDIC, 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.

 Examples

    This command reads an EBCDIC tape, blocked ten 80-byte EBCDIC card images
    per record, into the ASCII file outfile:

       dd  if=/dev/rct0  of=outfile  ibs=800  cbs=80  conv=ascii,lcase

    Note the use of raw magtape.  dd is especially suited to I/O on raw phy-
    sical devices because it allows reading and writing in arbitrary record
    sizes.

 See also

    copy(C), cp(C), tar(C)

 Diagnostics


    f+p records in(out)     Numbers of full and partial records read (writ-
                            ten)

 Notes

    The ASCII/EBCDIC conversion tables are taken from the 256-character stan-
    dard in the CACM Nov, 1968.  The ibm conversion 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.

    When using dd with a raw device, specify the block size as a multiple of
    1K.  For example, to use a 9K block size, enter:

       dd if=file of=/dev/rct0 bs=18b

    You could also enter:

       dd if=file of=/dev/rct0 bs=9K


 Standards conformance

    dd is conformant with:

    AT&T SVID Issue 2;
    and X/Open Portability Guide, Issue 3, 1989.