ddd(1l) [bsd man page]

DDD(1L) 																   DDD(1L)

NAME

       ddd - double-speed data dumper

SYNOPSIS

       ddd [option=value] ...

DESCRIPTION

       Ddd  works  almost  the	same  way  as dd(1), but it has a much better throughput, especially when used with slow i/o-devices, such as tape
       drives.	The improvement is achieved mainly by dividing the copying process into two processes, one of which  reads  while  the	other  one
       writes  and  vice  versa.  Also all code conversion capabilities are omitted.  There is no additional overhead copying data between various
       conversion buffers.

       Ddd was inspired by the vast difference in speed between BSD4.2 and BSD4.3 dumps - in BSD4.3 dump(8) uses alternating processes to write to
       raw  magnetic tape, thus keeping the tape continuously in motion.  I wanted to get the same improvement to remote dumps, so this filter was
       needed.	Directing all physical I/O through ddd usually increases the throughput of any pipeline of unix commands (if you have enough  MIPS
       and RAM to handle two extra processes).

OPTIONS

       Ddd  uses  options  if,	of,  ibs and obs exactly as dd(1).  Option bs can also be used to specify ibs and obs at once.	One option differs
       slightly in meaning: cbs can be used to specify the size of the internal buffer.  Input and output processes  will  swap  duties  when  cbs
       bytes  have  been transferred.  Default values for all sizes are 512 bytes.  As with dd(1), letters k (kilobyte), b (block) or w (word) can
       be appended to size values.  Other options are not provided.

HINTS

       For best performance, block sizes should be rather large.  For magnetic tape, I use obs=100b and cbs=500b or so.  Large block sizes (~100b)
       are  also  effective  for  network connections.	However, cbs should be small enough for all the data to fit in core, since page faults add
       overhead.

AUTHOR

       Tapani Lindgren <nispa@cs.hut.fi>
       Laboratory of Information Processing Science
       Helsinki University of Technology
       Finland

SEE ALSO

       dd(1), tar(1), dump(8)

BUGS

       Should you find one, let me know!

WARNING

       (Applies to U.S. residents & citizens only)
       Do not use this program!  Get rid of it as soon as you can!  It will probably corrupt all your data, break down	your  computer	and  cause
       severe  injury to the operators.  Even reading the source code may give you a headache.	I warned you!  I will take no responsibility what-
       soever!

																	   DDD(1L)

Check Out this Related Man Page

DD(1)									FSF								     DD(1)

NAME

       dd - convert and copy a file

SYNOPSIS

       dd [OPTION]...

DESCRIPTION

       Copy a file, converting and formatting according to the options.

       bs=BYTES
	      force ibs=BYTES and obs=BYTES

       cbs=BYTES
	      convert BYTES bytes at a time

       conv=KEYWORDS
	      convert the file as per the comma separated keyword list

       count=BLOCKS
	      copy only BLOCKS input blocks

       ibs=BYTES
	      read BYTES bytes at a time

       if=FILE
	      read from FILE instead of stdin

       obs=BYTES
	      write BYTES bytes at a time

       of=FILE
	      write to FILE instead of stdout

       seek=BLOCKS
	      skip BLOCKS obs-sized blocks at start of output

       skip=BLOCKS
	      skip BLOCKS ibs-sized blocks at start of input

       --help display this help and exit

       --version
	      output version information and exit

       BLOCKS  and  BYTES  may	be  followed  by  the  following  multiplicative suffixes: xM M, c 1, w 2, b 512, kB 1000, K 1024, MB 1,000,000, M
       1,048,576, GB 1,000,000,000, G 1,073,741,824, and so on for T, P, E, Z, Y.  Each KEYWORD may be:

       ascii  from EBCDIC to ASCII

       ebcdic from ASCII to EBCDIC

       ibm    from ASCII to alternated EBCDIC

       block  pad newline-terminated records with spaces to cbs-size

       unblock
	      replace trailing spaces in cbs-size records with newline

       lcase  change upper case to lower case

       notrunc
	      do not truncate the output file

       ucase  change lower case to upper case

       swab   swap every pair of input bytes

       noerror
	      continue after read errors

       sync   pad every input block with NULs to ibs-size; when used

	      with block or unblock, pad with spaces rather than NULs

AUTHOR

       Written by Paul Rubin, David MacKenzie, and Stuart Kemp.

REPORTING BUGS

       Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

       Copyright (C) 2002 Free Software Foundation, Inc.
       This is free software; see the source for copying conditions.  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
       LAR PURPOSE.

SEE ALSO

       The full documentation for dd is maintained as a Texinfo manual.  If the info and dd programs are properly installed at your site, the com-
       mand

	      info dd

       should give you access to the complete manual.

dd (coreutils) 4.5.3						   February 2003							     DD(1)

Linux and UNIX Man Pages

ddd(1l) [bsd man page]

Check Out this Related Man Page