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 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 | |
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/>
COPYRIGHT
Copyright © 2009 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' | |