from HTYP, the free directory anyone can edit if they can prove to me that they're not a spambot
< cmd(Redirected from dd)
Jump to navigation Jump to search



dd - convert and copy a file


dd [OPTION]...


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 


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


Report bugs to <>.


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 coreutils dd 

should give you access to the complete manual.

Edit Log

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