dd - convert and copy a file
Copy a file, converting and formatting according to the operands.
read and write up to BYTES bytes at a time
convert BYTES bytes at a time
convert the file as per the comma separated symbol list
copy only N input blocks
read up to BYTES bytes at a time (default: 512)
read from FILE instead of stdin
read as per the comma separated symbol list
write BYTES bytes at a time (default: 512)
write to FILE instead of stdout
write as per the comma separated symbol list
seek=N skip N obs-sized blocks at start of output
skip=N skip N ibs-sized blocks at start of input
WHICH info to suppress outputting to stderr; 'noxfer' suppresses transfer stats, 'none' suppresses all
N 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
replace trailing spaces in cbs-size records with newline
lcase change upper case to lower case
ucase change lower case to upper case
sparse try to seek rather than write the output for NUL input blocks
swab swap every pair of input bytes
sync pad every input block with NULs to ibs-size; when used with block or unblock, pad with spaces rather than NULs
excl fail if the output file already exists
do not create the output file
do not truncate the output file
continue after read errors
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
fail unless a directory
dsync use synchronized I/O for data
sync likewise, but also for metadata
accumulate full blocks of input (iflag only)
use non-blocking I/O
do not update access time
discard cached data
noctty do not assign controlling terminal from file
do not follow symlinks
treat 'count=N' as a byte count (iflag only)
treat 'skip=N' as a byte count (iflag only)
treat 'seek=N' as a byte count (oflag only)
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
output version information and exit
Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
Report dd bugs to email@example.com
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report dd translation bugs to <http://translationproject.org/team/>
Copyright © 2013 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.
The full documentation for dd is maintained as a Texinfo manual. If the info and dd programs are properly installed at your site, the command
info coreutils 'dd invocation'
should give you access to the complete manual.