dd(1) — Linux manual page


DD(1)                         User Commands                        DD(1)

NAME         top

       dd - convert and copy a file

SYNOPSIS         top

       dd [OPERAND]...
       dd OPTION

DESCRIPTION         top

       Copy a file, converting and formatting according to the operands.

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

              convert BYTES bytes at a time

              convert the file as per the comma separated symbol list

              copy only N input blocks

              read up to BYTES bytes at a time (default: 512)

              read from FILE instead of stdin

              read as per the comma separated symbol list

              write BYTES bytes at a time (default: 512)

              write to FILE instead of stdout

              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

              The LEVEL of information to print to stderr; 'none'
              suppresses everything but error messages, 'noxfer'
              suppresses 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

       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

              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

              do not create the output file

              do not truncate the output file

              continue after read errors

              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

       direct use direct I/O for data

              fail unless a directory

       dsync  use synchronized I/O for data

       sync   likewise, but also for metadata

              accumulate full blocks of input (iflag only)

              use non-blocking I/O

              do not update access time

              Request to drop cache.  See also oflag=sync

       noctty do not assign controlling terminal from file

              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.

       Options are:

       --help display this help and exit

              output version information and exit

AUTHOR         top

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

REPORTING BUGS         top

       GNU coreutils online help:
       Report any translation bugs to

COPYRIGHT         top

       Copyright © 2024 Free Software Foundation, Inc.  License GPLv3+:
       GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute
       it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO         top

       Full documentation <https://www.gnu.org/software/coreutils/dd>
       or available locally via: info '(coreutils) dd invocation'

COLOPHON         top

       This page is part of the coreutils (basic file, shell and text
       manipulation utilities) project.  Information about the project
       can be found at ⟨http://www.gnu.org/software/coreutils/⟩.  If you
       have a bug report for this manual page, see
       ⟨http://www.gnu.org/software/coreutils/⟩.  This page was obtained
       from the tarball coreutils-9.5.tar.xz fetched from
       ⟨http://ftp.gnu.org/gnu/coreutils/⟩ on 2024-06-14.  If you
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       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

GNU coreutils 9.5              March 2024                          DD(1)

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