| DD(1) | User Commands | 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 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=N
- copy only N 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=N
- skip N obs-sized blocks at start of output
- skip=N
- skip N ibs-sized blocks at start of input
- status=LEVEL
- The LEVEL of information to print to stderr; 'none' suppresses everything but error messages, 'noxfer' suppresses the final transfer statistics, 'progress' shows periodic transfer statistics
N 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
- sparse
- try to seek rather than write the output for NUL input blocks
- 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
- count_bytes
- treat 'count=N' as a byte count (iflag only)
- skip_bytes
- treat 'skip=N' as a byte count (iflag only)
- seek_bytes
- treat 'seek=N' as a byte count (oflag only)
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:
GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report dd translation bugs to <http://translationproject.org/team/>
AUTHOR¶
Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
COPYRIGHT¶
Copyright © 2013 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.
| November 2020 | GNU coreutils 8.22 |