dd

DD(1)                            User Commands                           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
              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 suf‐
       fixes: 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 sug‐
              gested)

       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 sta‐
       tistics 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: 
       General help using GNU software: 

COPYRIGHT
       Copyright © 2009 Free Software Foundation, Inc.   License  GPLv3+:  GNU
       GPL version 3 or later .
       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 com‐
       mand

              info coreutils 'dd invocation'

       should give you access to the complete manual.



GNU coreutils 7.4               September 2010                           DD(1)