dd - Linux Man Page

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 suf-
      fixes: 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:


      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 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