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 BYTES bytes at a time (also see ibs=,obs=)
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 (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
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
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
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.
$ 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

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/coreutils/> General help using GNU software: <http://www.gnu.org/gethelp/>

COPYRIGHT


Copyright © 2009 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.

openSUSE Logo

Contents