DD

DD(1)                           User Commands                          DD(1)

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

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 skip N obs-sized blocks at start of output

skip=N skip N ibs-sized blocks at start of input

status=WHICH
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

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 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

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
discard cached data

noctty do not assign controlling terminal from file

nofollow
do not follow symlinks

count_bytes
treat ‘count=N’ as a byte count (iflag only)

skip_bytes
treat ‘skip=N’ as a byte count (iflag only)

seek_bytes
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

Options are:

–help display this help and exit

–version
output version information and exit

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

AUTHOR

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

COPYRIGHT

Copyright © 2014 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.

COLOPHON

This page is part of the coreutils (basic file, shell and text
manipulation utilities) project.  Information about the project can
be found at ⟨http://www.gnu.org/software/coreutils/⟩.  If you have a
bug report for this manual page, see
⟨http://www.gnu.org/software/coreutils/⟩.  This page was obtained from
the tarball coreutils-8.23.tar.xz fetched from
⟨http://www.gnutls.org/download.html⟩ on 2014-12-30.  If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to [email protected]

GNU coreutils 8.23              December 2014                          DD(1)

Author:

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