dd
(1g)
Name
dd - convert and copy a file
Synopsis
dd [OPERAND]...
dd OPTION
Description
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 op-
erands.
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=noxfer
suppress transfer statistics
BLOCKS and BYTES may be followed by the following multi-
plicative suffixes: c =1, w =2, b =512, kB =1000, K =1024,
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User Commands DD(1)
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 new-
line
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
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User Commands DD(1)
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 copy-
ing.
$ dd if=/dev/zero of=/dev/null& pid=$!
$ kill -USR1 $pid; sleep 1; kill $pid
18335302+0 records in 18335302+0 records out 9387674624
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User Commands DD(1)
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/core-
utils/>
General help using GNU software: <http://www.gnu.org/geth-
elp/>
Report dd translation bugs to <http://translationpro-
ject.org/team/>
COPYRIGHT
Copyright (C) 2012 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 redis-
tribute it. There is NO WARRANTY, to the extent permitted
by law.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+--------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------+
|Availability | file/gnu-coreutils |
+---------------+--------------------+
|Stability | Uncommitted |
+---------------+--------------------+
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.
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User Commands DD(1)
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://ftp.gnu.org/gnu/coreutils/coreutils-8.16.tar.xz
Further information about this software can be found on the
open source community website at http://www.gnu.org/soft-
ware/coreutils/.
GNU coreutils 8.16 Last change: March 2012 5