dd – convert and copy a file
Copy a file, converting and formatting according to the operands.
- force ibs=BYTES and obs=BYTES
- convert BYTES bytes at a time
- convert the file as per the comma separated symbol list
- copy only BLOCKS input blocks
- read BYTES bytes at a time
- read from FILE instead of stdin
- read as per the comma separated symbol list
- write BYTES bytes at a time
- write to FILE instead of stdout
- write as per the comma separated symbol list
- skip BLOCKS obs-sized blocks at start of output
- skip BLOCKS ibs-sized blocks at start of input
- 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:
- from EBCDIC to ASCII
- from ASCII to EBCDIC
- from ASCII to alternate EBCDIC
- pad newline-terminated records with spaces to cbs-size
- replace trailing spaces in cbs-size records with newline
- change upper case to lower case
- do not create the output file
- fail if the output file already exists
- do not truncate the output file
- change lower case to upper case
- swap every pair of input bytes
- continue after read errors
- pad every input block with NULs to ibs-size; when used with block or unblock, pad with spaces rather than NULs
- physically write output file data before finishing
- likewise, but also write metadata
EachFLAG symbol may be:
- append mode (makes sense only for output; conv=notrunc suggested)
- 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
- display this help and exit
- output version information and exit
Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
Report bugs to <firstname.lastname@example.org>.
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.
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.