Manual: gnudd

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 up to BYTES bytes at a time (default: 512); overrides ibs and obs

       cbs=BYTES
	      convert BYTES bytes at a time

       conv=CONVS
	      convert the file as per the comma separated symbol list

       count=N
	      copy only N input blocks

       ibs=BYTES
	      read up to 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=N (or oseek=N) skip N obs-sized output blocks

       skip=N (or iseek=N) skip N ibs-sized input blocks

       status=LEVEL
	      The  LEVEL  of  information to print to stderr; 'none' suppresses everything but error messages, 'noxfer' sup‐
	      presses the final transfer statistics, 'progress' shows periodic transfer statistics

       N and BYTES may be followed by the following multiplicative suffixes: 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, R, Q.  Binary  prefixes  can  be
       used, too: KiB=K, MiB=M, and so on.  If N ends in 'B', it counts bytes not blocks.

       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

       ucase  change lower case to upper case

       sparse try to seek rather than write all-NUL output blocks

       swab   swap every pair of input bytes

       sync   pad every input block with NULs to ibs-size; when used with block or unblock, pad with spaces rather than NULs

       excl   fail if the output file already exists

       nocreat
	      do not create the output file

       notrunc
	      do not truncate the output file

       noerror
	      continue after read errors

       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

       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

       nocache
	      Request to drop cache.  See also oflag=sync

       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 copy‐
       ing.

       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
       GNU coreutils online help: 
       Report any translation bugs to 

SEE ALSO
       Full documentation 
       or available locally via: info '(coreutils) dd invocation'

       Packaged by Ubuntu (9.7-3ubuntu2)
       Copyright © 2025 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.

GNU coreutils 9.7					January 2026						       DD(1)