DD linux command manual
DD(1) User Commands DD(1)
dd - convert and copy a file
Copy a file, converting and formatting according to the options.
force ibs=BYTES and obs=BYTES
convert BYTES bytes at a time
convert the file as per the comma separated keyword list
copy only BLOCKS input blocks
read BYTES bytes at a time
read from FILE instead of stdin
write BYTES bytes at a time
write to FILE instead of stdout
skip BLOCKS obs-sized blocks at start of output
skip BLOCKS ibs-sized blocks at start of input
--help display this help and exit
output version information and exit
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 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
replace trailing spaces in cbs-size records with newline
lcase change upper case to lower case
do not truncate the output file
ucase change lower case to upper case
swab swap every pair of input bytes
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
Note that sending a SIGUSR1 signal to a running 'dd' process makes it
print to standard error the number of records read and written so far,
then to resume copying.
$ dd if=/dev/zero of=/dev/null& pid=$!
$ kill -USR1 $pid; sleep 1; kill $pid
10899206+0 records in 10899206+0 records out
Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
Report bugs to .
Copyright (C) 2004 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-
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-
info coreutils dd
should give you access to the complete manual.
dd (coreutils) 5.2.1 May 2004 DD(1)