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1. Name

dd - convert and copy a file

2. Synopsis

dd [OPERAND]...
dd OPTION

3. Description

Copy a file, converting and formatting according to the operands.

bs=BYTES
force ibs=BYTES and obs=BYTES
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 BYTES bytes at a time
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
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: xM M, c 1, w 2, b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, 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
nocreat
do not create the output file
excl
fail if the output file already exists
notrunc
do not truncate the output file
ucase
change lower case to upper case
swab
swap every pair of input bytes
noerror
continue after read errors
sync
pad every input block with NULs to ibs-size; when used with block or unblock, pad with spaces rather than NULs
fdatasync
physically write output file data before finishing
fsync
likewise, but also write metadata

EachFLAG 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 nonblock use non-blocking I/O noatime do not update access time 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.

CW$ dd if=/dev/zero of=/dev/null& pid=$!

CW$ 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

4. Author

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

5. Reporting Bugs

Report bugs to <This email address is being protected from spambots. You need JavaScript enabled to view it. >. Copyright © 2008 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.

7. See Also

The full documentation for dd is maintained as a Texinfo manual. If the info and dd programs are properly installed atyour site, the command
info coreutils ’dd invocation’

should give you access to the complete manual.

 


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