DD(1)
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 sug
- gested)
- 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/>
Report dd translation bugs to <http://translationproject.org/team/>
COPYRIGHT
Copyright (C) 2010 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.