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
--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 <email@example.com>.
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
should give you access to the complete manual.
dd (coreutils) 5.97 March 2012 DD(1)