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

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 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

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 suggested)

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

AUTHOR¶

Written by Paul Rubin, David MacKenzie, and Stuart Kemp.

REPORTING BUGS¶

Report dd bugs to bug-coreutils@gnu.org
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¶

Copyright © 2010 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.

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 command

info coreutils 'dd invocation'

should give you access to the complete manual.