DD(1) User Commands September 2011

dd - convert and copy a file

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=BLOCKS
copy only BLOCKS 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=BLOCKS
skip BLOCKS obs-sized blocks at start of output
skip=BLOCKS
skip BLOCKS ibs-sized blocks at start of input
status=noxfer
suppress transfer statistics

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
ucase
change lower case to upper case
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

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

Report dd bugs to [email protected]
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/>

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

should give you access to the complete manual.