---
name: "dd"
section: "1"
platform: "linux"
package: "coreutils"
version: "9.12-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/dd"
---

# dd(1)

convert and copy a file

## 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 standard input

- **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 standard output

- **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 standard error; '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 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 copying.

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 bugs to: \<bug-coreutils@gnu.org\>.\
 Report any translation bugs to: \<https://translationproject.org/team/\>.\
 GNU coreutils home page: \<https://www.gnu.org/software/coreutils/\>\
 General help using GNU software: \<https://www.gnu.org/gethelp/\>

## COPYRIGHT

Copyright © 2026 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

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