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 up to BYTES bytes at a time (default: 512); overrides ibs and 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 up to 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=N

(or oseek=N) skip N obs-sized output blocks

skip=N

(or iseek=N) skip N ibs-sized input blocks

status=LEVEL

The LEVEL of information to print to stderr; 'none' suppresses everything but error messages, 'noxfer' suppresses the final transfer statistics, 'progress' shows periodic transfer statistics

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. Binary prefixes can be used, too: KiB=K, MiB=M, and so on. If N ends in 'B', it counts bytes not blocks.

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

ucase

change lower case to upper case

sparse

try to seek rather than write all-NUL output 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

nocreat

do not create the output file

notrunc

do not truncate the output file

noerror

continue after read errors

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

nocache

Request to drop cache. See also oflag=sync

noctty

do not assign controlling terminal from file

nofollow

do not follow symlinks

Sending a USR1 signal to a running 'dd' process makes it print I/O statistics to standard error and then resume copying.

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¶

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report any translation bugs to <https://translationproject.org/team/>

COPYRIGHT¶

Copyright © 2022 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://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¶

Full documentation <https://www.gnu.org/software/coreutils/dd>
or available locally via: info '(coreutils) dd invocation'