DD

Section: User Commands (1)
Updated: March 2004
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NAME

dd - convert and copy a file

SYNOPSIS

dd [OPTION]...

DESCRIPTION

Copy a file, converting and formatting according to the options.

bs=BYTES: force ibs=BYTES and obs=BYTES
cbs=BYTES: convert BYTES bytes at a time
conv=KEYWORDS: convert the file as per the comma separated keyword list
count=BLOCKS: copy only BLOCKS input blocks
ibs=BYTES: read BYTES bytes at a time
if=FILE: read from FILE instead of stdin
obs=BYTES: write BYTES bytes at a time
of=FILE: write to FILE instead of stdout
seek=BLOCKS: skip BLOCKS obs-sized blocks at start of output
skip=BLOCKS: skip BLOCKS ibs-sized blocks at start of input
--help: display this help and exit
--version: output version information and exit

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 KEYWORD may be:

ascii: from EBCDIC to ASCII
ebcdic: from ASCII to EBCDIC
ibm: from ASCII to alternated 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
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

Note that sending a SIGUSR1 signal to a running `dd' process makes it print to standard error the number of records read and written so far, then to resume copying.

: $ dd if=/dev/zero of=/dev/null& pid=$!
$ kill -USR1 $pid; sleep 1; kill $pid
: 10899206+0 records in 10899206+0 records out

AUTHOR

Written by Paul Rubin, David MacKenzie, and Stuart Kemp.

REPORTING BUGS

Report bugs to <bug-coreutils@gnu.org>.

COPYRIGHT

DD