dd man page on aLinux

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DD(1)				 User Commands				 DD(1)

NAME
       dd - convert and copy a file

SYNOPSIS
       dd [OPERAND]...
       dd OPTION

DESCRIPTION
       Copy a file, converting and formatting according to the operands.

       bs=BYTES
	      force ibs=BYTES and obs=BYTES

       cbs=BYTES
	      convert BYTES bytes at a time

       conv=CONVS
	      convert the file as per the comma separated symbol list

       count=BLOCKS
	      copy only BLOCKS input blocks

       ibs=BYTES
	      read BYTES bytes at a time

       if=FILE
	      read from FILE instead of stdin

       iflag=FLAGS
	      read as per the comma separated symbol list

       obs=BYTES
	      write BYTES bytes at a time

       of=FILE
	      write to FILE instead of stdout

       oflag=FLAGS
	      write as per the comma separated symbol list

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

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

       status=noxfer
	      suppress transfer statistics

       BLOCKS  and  BYTES may be followed by the following multiplicative suf‐
       fixes: xM M, c 1, w 2,  b  512,	kB  1000,  K  1024,  MB	 1000*1000,  M
       1024*1024,  GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E,
       Z, Y.

       Each CONV symbol may be:

       ascii  from EBCDIC to ASCII

       ebcdic from ASCII to EBCDIC

       ibm    from ASCII to alternate 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

       nocreat
	      do not create the output file

       excl   fail if the output file already exists

       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

       fdatasync
	      physically write output file data before finishing

       fsync  likewise, but also write metadata

       Each FLAG symbol may be:

       append append  mode  (makes  sense  only	 for output; conv=notrunc sug‐
	      gested)

       direct use direct I/O for data

	      directory fail unless a directory dsync	  use synchronized I/O
	      for data sync	 likewise, but also for metadata nonblock  use
	      non-blocking I/O noatime	 do  not  update  access  time	noctty
	      do  not  assign  controlling terminal from file nofollow	do not
	      follow symlinks

       Sending a USR1 signal to a running `dd' process makes it print I/O sta‐
       tistics to standard error and then resume copying.

	      $ dd if=/dev/zero of=/dev/null& pid=$!
	      $ kill -USR1 $pid; sleep 1; kill $pid

	      18335302+0  records  in  18335302+0 records out 9387674624 bytes
	      (9.4 GB) copied, 34.6279 seconds, 271 MB/s

       Options are:

       --help display this help and exit

       --version
	      output version information and exit

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

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

COPYRIGHT
       Copyright © 2008 Free Software Foundation, Inc.	 License  GPLv3+:  GNU
       GPL version 3 or later <http://gnu.org/licenses/gpl.html>
       This  is	 free  software:  you  are free to change and redistribute it.
       There is NO WARRANTY, to the extent permitted by law.

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.

GNU coreutils 6.9.92.4-f088d-dirtJanuary 2008				 DD(1)
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