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)

direct use direct I/O for data

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

nofollow do not follow symlinks

noctty do not assign controlling terminal from file

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

COPYRIGHT Copyright © 2006 Free Software Foundation, Inc. This is free software. You may redistribute copies of it under the terms of the GNU General Public License <http://www.gnu.org/licenses/gpl.html>. 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.

dd (coreutils) 5.97 March 2012 DD(1)