Editing Null device (section)

{{Short description|Device file that discards all data written to it}}
{{For|the electropop band|Null Device}}
{{Confuse|/dev/zero}}
{{Use dmy dates|date=February 2020|cs1-dates=y}}

In some [[operating system]]s, the '''null device''' is a [[device file]] that discards all data written to it but reports that the write operation succeeded. This device is called <code>/dev/null</code> on [[Unix]] and [[Unix-like]] systems, <code>NUL:</code> (see [[TOPS-20]]) or <code>NUL</code> on [[CP/M]] and [[DOS]] (internally <code>\DEV\NUL</code>), <code>nul</code> on [[OS/2]] and newer [[Windows]] systems<ref>{{Cite web|url=https://support.microsoft.com/en-us/help/110930/redirecting-error-messages-from-command-prompt-stderr-stdout|title=Redirecting Error Messages from Command Prompt: STDERR/STDOUT|website=support.microsoft.com|access-date=2020-03-06}}</ref> (internally <code>\Device\Null</code> on [[Windows NT]]), <code>NIL:</code> on [[Amiga]] operating systems,<ref>{{cite book |author=Commodore-Amiga, Inc. |title=The AmigaDOS Manual |date=1986 |publisher=Bantam Books |isbn=0-553-34294-0 |page=12 |url=https://archive.org/details/TheAmigaDOSUsersManual3In1Manual/page/n17/mode/2up }}</ref> and <code>NL:</code> on [[OpenVMS]].<ref>{{Cite web|url=http://h30266.www3.hpe.com/odl/vax/opsys/vmsos73/vmsos73/5841/5841pro_064.html|title=OpenVMS Programming Concepts Manual|website=h30266.www3.hpe.com|access-date=2020-03-06|archive-date=2020-07-02 |archive-url=https://web.archive.org/web/20200702065120/http://h30266.www3.hpe.com/odl/vax/opsys/vmsos73/vmsos73/5841/5841pro_064.html|url-status=dead}}</ref> In [[Windows Powershell]], the equivalent is <code>$null</code>.<ref>{{Cite web|url=https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_automatic_variables|title=about_Automatic_Variables - PowerShell|last=SteveL-MSFT|website=docs.microsoft.com|language=en-us|access-date=2020-03-06}}</ref> It provides no data to any [[process (computing)|process]] that reads from it, yielding [[end-of-file|EOF]] immediately.<ref name="uxman">{{cite web|url=http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap10.html |title=Single Unix Specification Section 10.1: Directory Structure and Files |publisher=The Open Group |access-date=2012-11-29}}</ref> In IBM operating systems  [[DOS/360 and successors]]{{efn|The most recent being [[z/VSE]].}} and also in [[OS/360 and successors]]{{efn|The most recent being [[z/OS]].}} such files would be assigned in [[job control language|JCL]] to <code>DD DUMMY</code>.

In programmer jargon, especially Unix jargon, it may also be called the [[bit bucket]]<ref>{{cite web|title=bit bucket|url=http://catb.org/esr/jargon/html/B/bit-bucket.html|work=Jargon File|access-date=2013-12-27}}</ref> or [[Black hole (networking)|black hole]].