Table of Contents
dd - convert and copy a file
dd [OPERAND]...
dd OPTION
Copy a file, converting and formatting according
to the operands.
- bs=BYTES
- force ibs=BYTES and obs=BYTES
- 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
- 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
- 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: 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:
- 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)
- direct
- use direct I/O for data
- dsync
- use synchronized
I/O for data
- sync
- likewise, but also for metadata
- nonblock
- use non-blocking
I/O
- nofollow
- do not follow symlinks
- noctty
- do not assign controlling terminal
from file
Sending a SIGUSR1 signal to a running ‘dd’ process makes it print
I/O statistics to standard error, then to 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
Options
are:
- --help
- display this help and exit
- --version
- output version information
and exit
Written by Paul Rubin, David MacKenzie, and Stuart Kemp.
Report bugs to <bug-coreutils@gnu.org>.
Copyright © 2004
Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is
NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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 dd
should give you access to the complete manual.
Table of Contents