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
	      read and write BYTES bytes at a time (also see ibs=,obs=)

       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 (default: 512)

       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 (default: 512)

       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 suffixes: c =1, w =2, b =512, kB =1000, K =1024, MB =1000*1000, M
       =1024*1024, xM =M 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 suggested)

       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

       fullblock
	      accumulate full blocks of input (iflag only)

       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 statistics 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 dd bugs to bug-coreutils@gnu.org
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>

COPYRIGHT

       Copyright (C) 2009 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 coreutils 'dd invocation'

       should give you access to the complete manual.

GNU coreutils 7.1						     July 2010								     DD(1)