cmd/dd

Documentation

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

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.

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 

should give you access to the complete manual.

Edit Log

• 2005-06-25 Created from Linux manpage (Ubuntu hoary)