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
    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; conv=notrunc suggested)

direct
    use direct I/O for data

FLAG symbols only for iflag option:

fullblock
    Read full blocks from input if possible. read() may return early if a full block is not available, so retry until data is available or end of file is reached.

    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.

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

COPYRIGHT
Copyright © 2007 Free Software Foundation, Inc.
This is free software. You may redistribute copies of it under the terms of the GNU General Public License <http://www.gnu.org/licenses/gpl.html>. 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 dd

should give you access to the complete manual.