DD
Section: User Commands (1)
Updated: September 2017
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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
-
skip N obs-sized blocks at start of output
- skip=N
-
skip N ibs-sized blocks at start of input
- 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.
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
-
Request to drop cache. See also oflag=sync
- 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.
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: <
http://www.gnu.org/software/coreutils/>
Report dd translation bugs to <
http://translationproject.org/team/>
COPYRIGHT
Copyright © 2017 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
Full documentation at: <
http://www.gnu.org/software/coreutils/dd>
or available locally via: info aq(coreutils) dd invocationaq
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- AUTHOR
-
- REPORTING BUGS
-
- COPYRIGHT
-
- SEE ALSO
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