Editing Dd (Unix) (section)

{{Lowercase title}}
{{short description|Shell command for copying and converting file data}}
{{Infobox software
| name                   = dd
| logo                   = 
| screenshot             = 
| screenshot size        = 
| caption                = 
| author                 = [[Ken Thompson]]<br />([[AT&T Bell Laboratories]])
| developer              = Various [[open-source software|open-source]] and [[commercial software|commercial]] developers
| released               = {{Start date and age|1974|6}}
| latest release version = 
| latest release date    = 
| programming language   = Plan 9: [[C (programming language)|C]]
| operating system       = [[Unix]], [[Unix-like]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], [[Windows]]
| platform               = [[Cross-platform]]
| genre                  = [[Command (computing)|Command]]
| license                = [[coreutils]]: [[GPLv3+]]<br />Plan 9: [[MIT License]]
| repo                   = coreutils: {{URL|https://git.savannah.gnu.org/cgit/coreutils.git/}}
| website                = 
}}
<code>'''dd'''</code> is [[Shell (computing)|shell]] [[command (computing)|command]] for reading, writing and converting [[computer file|file]] [[data]]. Originally developed for [[Unix]], it has been implemented on many other environments including [[Unix-like]] [[operating system]]s, [[Microsoft Windows|Windows]], [[Plan 9 from Bell Labs|Plan 9]] and [[Inferno (operating system)|Inferno]].<ref name="OpenGroup-dd-man">{{cite web | url=http://www.opengroup.org/onlinepubs/9699919799/utilities/dd.html | title=POSIX standard: dd invocation | author=Austin Group | access-date=2016-09-29 | archive-date=2010-03-10 | archive-url=https://web.archive.org/web/20100310213820/http://www.opengroup.org/onlinepubs/9699919799/utilities/dd.html | url-status=live }}</ref> 

The command can be used for many purposes. For relatively simple copying operations, it tends to be slower than domain-specific alternatives, but it excels at overwriting or truncating a file at any point or seeking in a file.<ref name=relevant>{{cite web |last1=Gilles |title=cloning - dd vs cat – is dd still relevant these days? |url=https://unix.stackexchange.com/a/12538 |website=Unix & Linux Stack Exchange |date=2011 |access-date=2020-04-24 |archive-date=2023-10-24 |archive-url=https://web.archive.org/web/20231024083153/https://unix.stackexchange.com/questions/12532/dd-vs-cat-is-dd-still-relevant-these-days/12538#12538 |url-status=live }}</ref>

The command supports reading and writing files, and if a [[device driver|driver]] is available to support file-like access, the command can access devices too. Such access is typically supported on Unix-based systems that provide file-like access to devices (such as [[computer data storage|storage]]) and special [[device file]]s (such as [[/dev/zero]] and [[/dev/random]]). Therefore, the command can be used for tasks such as backing up the [[boot sector]] of a drive, and obtaining random data. 

The command can also support converting data while copying; including [[byte order]] swapping and converting between [[ASCII]] and [[EBCDIC]] text encodings.<ref name="tfl-dd">{{cite web |last=Chessman |first=Sam |title=How and when to use the dd command? |url=http://www.codecoffee.com/tipsforlinux/articles/036.html |archive-url=https://web.archive.org/web/20080214125249/http://www.codecoffee.com/tipsforlinux/articles/036.html |archive-date=14 Feb 2008 |access-date=2008-02-19 |publisher=CodeCoffee |url-status=dead}}</ref>

<code>dd</code> is sometimes humorously called "Disk Destroyer", due to its drive-erasing capabilities involving [[Typographical error|typos]].<ref>{{Cite web|date=2018-07-05|title=How to use dd in Linux without destroying your disk|url=https://opensource.com/article/18/7/how-use-dd-linux|access-date=2020-10-11|website=Opensource.com|language=en|archive-date=2020-10-11|archive-url=https://web.archive.org/web/20201011054921/https://opensource.com/article/18/7/how-use-dd-linux|url-status=live}}</ref>