Category

Linux Command


Usage

dd OPTION


Manual

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=N
copy only N 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=WHICH
WHICH info to suppress outputting to stderr; ’noxfer’ suppresses
transfer stats, ’none’ suppresses all

BLOCKS and BYTES may be followed by the following multiplicative suf-
fixes: 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

sparse try to seek rather than write the output for NUL input blocks

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 sug-
gested)

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

count_bytes
treat ’count=N’ as a byte count (iflag 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

Options are:

--help display this help and exit

--version
output version information and exit


Share your experience or ask a question