Manual Reference Pages  - DD (1)

NAME

dd - convert and copy a file

CONTENTS

Synopsis
Description
Author
Copyright

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.
$ 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/>
Report dd translation bugs to <http://translationproject.org/team/>

COPYRIGHT

Copyright © 2011 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.


GNU coreutils 8.12.197-032bb DD (1) September 2011
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