dd(1)							      General Commands Manual							     dd(1)

NAME

       dd - convert, reblock, translate, and copy a (tape) file

SYNOPSIS

       [optionvalue] ...

DESCRIPTION

       copies the specified input file to the specified output file with possible conversions.	The standard input and output are used by default.
       Input and output block size can be specified to take advantage of raw physical I/O.  Upon completion, reports the number of whole and  par-
       tial input and output records.

   Options
       recognizes the following pairs:

	      Input file name; default is standard input.

	      Output file name; default is standard output.
			     The output file is created using the same owner and group used by

	      Input block size is
			     n bytes; default is 512.

	      Output block size is
			     n bytes; default is 512.

	      Set both input and output block size to the same size, superseding
			     and This option is particularly efficient if no conversion is specified, because no in-core copy is necessary.

	      Conversion buffer size is
			     n bytes.

	      Skip	     n input blocks before starting copy.

	      Skip	     n input blocks before starting copy.  (This is an alias for the option.)

	      Skip	     n blocks from beginning of output file before copying.

	      Skip	     n blocks from beginning of output file before copying.  (This is an alias for the option.)

	      Copy only      n input blocks.

	      Copy and concatenate
			     n input files.  This option should be used only when the input file is a magnetic tape device.

	      Where	     values are comma-separated symbols from the following list.

			     Convert EBCDIC    to ASCII.

			     Convert ASCII     to EBCDIC.

			     Convert ASCII to EBCDIC using an alternate conversion table.

					       The and values are mutually exclusive.

			     Convert each newline-terminated or end-of-file-terminated input record
					       to a record with a fixed length specified by Any newline character is removed, and space characters
					       are used to fill the block to size Lines that are longer than are truncated; the  number  of  trun-
					       cated lines (records) is reported (see below).

					       The values are mutually exclusive.

			     Convert fixed-length input records to variable-length records.
					       For each input record, bytes are read, trailing space characters are deleted, and a newline charac-
					       ter is appended.

			     Map upper-case input characters to the corresponding lower-case characters.

					       The values are mutually exclusive.

			     Map lower-case input characters to the corresponding upper-case characters.

			     Swap every pair of input bytes.

			     Do not stop processing on an input error.
					       If the conversion symbol is also specified, missing input is replaced with null bytes and processed
					       normally; otherwise, the input block is omitted from the output.

			     Do not truncate existing output file.
					       Blocks in the output file not overwritten by this invocation of are preserved.

			     Pad every input block to size
					       If is also specified, pad with space characters; otherwise, pad with null bytes.

       Where sizes are required, n indicates a numerical value in bytes.  Numbers can be specified using the forms:

	      n 	for n bytes
	      for	n Kbytes (n x 1024),
	      for	n blocks (n x 512), or
	      for	n words (n x 2).

       To indicate a product, use to separate number pairs.

       The  option  is used when or conversion is specified.  In case of cbs characters are placed into the conversion buffer, converted to ASCII,
       trailing blanks are trimmed, and a newline is added before sending the line to the output.  In case of ASCII characters are read  into  the
       conversion buffer, converted to EBCDIC, and blanks are added to make up an output block of size cbs.

EXTERNAL INFLUENCES

   International Code Set Support
       Single- and multi-byte character code sets are supported.

   Environment Variables
       The following environment variables affect execution of

       determines the locale when and a corresponding variable (beginning with do not specify a locale.

       determines the locale used to override any values set by or any environment variables beginning with

       The  variable determines the locale for the interpretation of sequences of bytes of text data as characters (single-byte/multi-byte charac-
       ters, upper-case/lower-case characters).

       The variable determines the language in which messages are written.

RETURN VALUE

       Exit values are:

	      Successful completion.
	      Error condition occurred.

DIAGNOSTICS

       Upon completion, reports the number of input and output records:

	      Number of full and partial blocks read.
	      Number of full and partial blocks written.

       When is specified and there is at least one truncated block, the number of truncated records is also reported:

EXAMPLES

       Read an EBCDIC tape blocked ten 80-byte EBCDIC card images per block into an ASCII file named

       Note the use of the raw magnetic tape device file.  is especially suited to I/O on raw physical devices because it allows reading and writ-
       ing in arbitrary block sizes.

WARNINGS

       Some devices, such as 1/2-inch magnetic tapes, are incapable of seeking.  Such devices may be positioned prior to running by using mt(1) or
       some other appropriate command.	The options do work for such devices.  However, skipping blocks using these options  is  slow  on  devices
       that cannot seek, since the blocks must actually be read to get to the desired position on the tape.

       ASCII and EBCDIC conversion tables are taken from the 256-character ACM standard, Nov, 1968.  The conversion, while less widely accepted as
       a standard, corresponds better to certain IBM print train conventions.  There is no universal solution.

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

       If  or  refers to a raw disk, should always be a multiple of the sector size of the disk.  By default, is 512 bytes.  If the sector size of
       the disk is different from 512 bytes, should be specified using a multiple of sector size.  The character special (raw) device file  should
       always be used for devices.

       It is entirely up to the user to insure there is enough room in the destination file, file system and/or device to contain the output since
       cannot pre-determine the required space after conversion.

SEE ALSO

       cp(1), mt(1), tr(1), disk(7), mt(7).

STANDARDS CONFORMANCE

																	     dd(1)