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setuid - Wikipedia
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cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Setuid" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Setuid" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Setuid" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Setuid" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"><!-- CentralNotice --></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-File_modes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#File_modes"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>File modes</span> </div> </a> <ul id="toc-File_modes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Effects" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Effects"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Effects</span> </div> </a> <button aria-controls="toc-Effects-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Effects subsection</span> </button> <ul id="toc-Effects-sublist" class="vector-toc-list"> <li id="toc-When_set_on_an_executable_file" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#When_set_on_an_executable_file"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>When set on an executable file</span> </div> </a> <ul id="toc-When_set_on_an_executable_file-sublist" class="vector-toc-list"> <li id="toc-Security_impact" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Security_impact"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1.1</span> <span>Security impact</span> </div> </a> <ul id="toc-Security_impact-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-When_set_on_a_directory" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#When_set_on_a_directory"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>When set on a directory</span> </div> </a> <ul id="toc-When_set_on_a_directory-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Examples" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Examples"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Examples</span> </div> </a> <button aria-controls="toc-Examples-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Examples subsection</span> </button> <ul id="toc-Examples-sublist" class="vector-toc-list"> <li id="toc-Checking_permissions" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Checking_permissions"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Checking permissions</span> </div> </a> <ul id="toc-Checking_permissions-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-SUID" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#SUID"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>SUID</span> </div> </a> <ul id="toc-SUID-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-SGID" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#SGID"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>SGID</span> </div> </a> <ul id="toc-SGID-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Sticky_bit" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Sticky_bit"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.4</span> <span>Sticky bit</span> </div> </a> <ul id="toc-Sticky_bit-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Sticky_bit_with_SGID" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Sticky_bit_with_SGID"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.5</span> <span>Sticky bit with SGID</span> </div> </a> <ul id="toc-Sticky_bit_with_SGID-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Security" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Security"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Security</span> </div> </a> <ul id="toc-Security-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-History" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#History"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>History</span> </div> </a> <ul id="toc-History-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading">setuid</h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 13 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-13" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">13 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Setuid" title="Setuid – Catalan" lang="ca" hreflang="ca" data-title="Setuid" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Setuid" title="Setuid – Czech" lang="cs" hreflang="cs" data-title="Setuid" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Setuid" title="Setuid – German" lang="de" hreflang="de" data-title="Setuid" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Setuid" title="Setuid – Spanish" lang="es" hreflang="es" data-title="Setuid" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Setuid" title="Setuid – Basque" lang="eu" hreflang="eu" data-title="Setuid" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Setuid" title="Setuid – French" lang="fr" hreflang="fr" data-title="Setuid" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Setuid_e_setgid" title="Setuid e setgid – Italian" lang="it" hreflang="it" data-title="Setuid e setgid" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-lmo mw-list-item"><a href="https://lmo.wikipedia.org/wiki/Setuid_e_setgid" title="Setuid e setgid – Lombard" lang="lmo" hreflang="lmo" data-title="Setuid e setgid" data-language-autonym="Lombard" data-language-local-name="Lombard" class="interlanguage-link-target"><span>Lombard</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/Setuid" title="Setuid – Japanese" lang="ja" hreflang="ja" data-title="Setuid" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Setuid" title="Setuid – Polish" lang="pl" hreflang="pl" data-title="Setuid" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Setuid" title="Setuid – Portuguese" lang="pt" hreflang="pt" data-title="Setuid" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/Suid" title="Suid – Russian" lang="ru" hreflang="ru" data-title="Suid" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Setuid" title="Setuid – Slovak" lang="sk" hreflang="sk" data-title="Setuid" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q269582#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div 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id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Setuid"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Setuid&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Setuid&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Setuid" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Setuid" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q"><span>Special pages</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Setuid&oldid=1217859762" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Setuid&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=Setuid&id=1217859762&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FSetuid"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FSetuid"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=Setuid&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Setuid&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q269582" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Unix access rights flag</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"SGID" redirects here. For the company which briefly used this stock ticker symbol, see <a href="/wiki/Silicon_Graphics" title="Silicon Graphics">Silicon Graphics</a>.</div> <p>The <a href="/wiki/Unix" title="Unix">Unix</a> and <a href="/wiki/Linux" title="Linux">Linux</a> access rights flags <b>setuid</b> and <b>setgid</b> (short for <i>set user identity</i> and <i>set group identity</i>)<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> allow users to run an <a href="/wiki/Executable" title="Executable">executable</a> with the <a href="/wiki/File_system_permissions" class="mw-redirect" title="File system permissions">file system permissions</a> of the executable's owner or group respectively and to change behaviour in directories. They are often used to allow users on a computer system to run programs with temporarily elevated privileges to perform a specific task. While the assumed user id or group id privileges provided are not always elevated, at a minimum they are specific. </p><p>The flags <code>setuid</code> and <code>setgid</code> are needed for tasks that require different privileges than what the user is normally granted, such as the ability to alter system files or databases to change their login password.<sup id="cite_ref-oreilly_2-0" class="reference"><a href="#cite_note-oreilly-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Some of the tasks that require additional privileges may not immediately be obvious, though, such as the <code><a href="/wiki/Ping_(networking_utility)" title="Ping (networking utility)">ping</a></code> command, which must send and listen for <a href="/wiki/Internet_Control_Message_Protocol" title="Internet Control Message Protocol">control packets</a> on a network interface. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="File_modes">File modes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=1" title="Edit section: File modes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <code>setuid</code> and <code>setgid</code> bits are normally represented as the values 4 for <code>setuid</code> and 2 for <code>setgid</code> in the high-order octal digit of the file mode. For example, <code>6711</code> has both the <code>setuid</code> and <code>setgid</code> bits (<span class="nowrap">4 + 2 = 6</span>) set, and also the file read/write/executable for the owner (7), and executable by the group (first 1) and others (second 1). Most implementations have a symbolic representation of these bits; in the previous example, this could be <code>u=rwx,go=x,ug+s</code>. </p><p>Typically, <code>chmod</code> does not have a recursive mode restricted to directories, so modifying an existing directory tree must be done manually, with a command such as <code class="mw-highlight mw-highlight-lang-sh mw-content-ltr" style="" dir="ltr">find<span class="w"> </span>/path/to/directory<span class="w"> </span>-type<span class="w"> </span>d<span class="w"> </span>-exec<span class="w"> </span>chmod<span class="w"> </span>g+s<span class="w"> </span><span class="s1">'{}'</span><span class="w"> </span><span class="s1">'\'</span></code>. </p> <div class="mw-heading mw-heading2"><h2 id="Effects">Effects</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=2" title="Edit section: Effects"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <code>setuid</code> and <code>setgid</code> flags have different effects, depending on whether they are applied to a file, to a directory or binary executable or non-binary executable file. The <code>setuid</code> and <code>setgid</code> flags have an effect only on binary executable files and not on scripts (e.g., Bash, Perl, Python).<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="When_set_on_an_executable_file">When set on an executable file</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=3" title="Edit section: When set on an executable file"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When the <code>setuid</code> or <code>setgid</code> attributes are set on an <a href="/wiki/Executable" title="Executable">executable</a> file, then any users able to execute the file will automatically execute the file with the privileges of the file's owner (commonly <a href="/wiki/Superuser" title="Superuser">root</a>) and/or the file's group, depending upon the flags set.<sup id="cite_ref-oreilly_2-1" class="reference"><a href="#cite_note-oreilly-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> This allows the system designer to permit trusted programs to be run which a user would otherwise not be allowed to execute. These may not always be obvious. For example, the <a href="/wiki/Ping_(networking_utility)" title="Ping (networking utility)">ping</a> command may need access to networking privileges that a normal user cannot access; therefore it may be given the setuid flag to ensure that a user who needs to ping another system can do so, even if their account does not have the required privilege for sending packets. </p> <div class="mw-heading mw-heading4"><h4 id="Security_impact">Security impact</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=4" title="Edit section: Security impact"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>For security purposes, the invoking user is usually prohibited by the system from altering the new process in any way, such as by using <code><a href="/wiki/Ptrace" title="Ptrace">ptrace</a></code>, <code>LD_LIBRARY_PATH</code> or sending signals to it, to exploit the raised privilege, although signals from the terminal will still be accepted. </p><p>While the <code>setuid</code> feature is very useful in many cases, its improper use can pose a security risk<sup id="cite_ref-oreilly_2-2" class="reference"><a href="#cite_note-oreilly-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> if the <code>setuid</code> attribute is assigned to <a href="/wiki/Executable" title="Executable">executable</a> programs that are not carefully designed. Due to potential security issues,<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> many operating systems ignore the <code>setuid</code> attribute when applied to executable <i><a href="/wiki/Shell_script" title="Shell script">shell scripts</a></i>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (March 2024)">citation needed</span></a></i>]</sup> </p><p>The presence of <code>setuid</code> executables explains why the <code><a href="/wiki/Chroot" title="Chroot">chroot</a></code> system call is not available to non-<a href="/wiki/Superuser" title="Superuser">root</a> users on Unix. See <a href="/wiki/Chroot#Limitations" title="Chroot">limitations of <code>chroot</code></a> for more details. </p> <div class="mw-heading mw-heading3"><h3 id="When_set_on_a_directory">When set on a directory</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=5" title="Edit section: When set on a directory"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Setting the <code>setgid</code> permission on a directory causes files and subdirectories created within to inherit its group ownership, rather than the primary group of the file-creating process. Created subdirectories also inherit the <code>setgid</code> bit. The policy is only applied during creation and, thus, only prospectively. Directories and files existing when the <code>setgid</code> bit is applied are unaffected, as are directories and files moved into the directory on which the bit is set. </p><p>Thus is granted a capacity to work with files amongst a group of users without explicitly setting permissions, but limited by the security model expectation that existing files permissions do not implicitly change. </p><p>The <code>setuid</code> permission set on a directory is ignored on most <a href="/wiki/UNIX" class="mw-redirect" title="UNIX">UNIX</a> and <a href="/wiki/Linux" title="Linux">Linux</a> systems.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (November 2017)">citation needed</span></a></i>]</sup> However <a href="/wiki/FreeBSD" title="FreeBSD">FreeBSD</a> can be configured to interpret <code>setuid</code> in a manner similar to <code>setgid</code>, in which case it forces all files and sub-directories created in a directory to be owned by that directory's owner - a simple form of inheritance.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> This is generally not needed on most systems derived from <a href="/wiki/BSD" class="mw-redirect" title="BSD">BSD</a>, since by default directories are treated as if their <code>setgid</code> bit is always set, regardless of the actual value. As is stated in <code>open(2)</code>, "When a new file is created it is given the group of the directory which contains it."<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Examples">Examples</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=6" title="Edit section: Examples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Checking_permissions">Checking permissions</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=7" title="Edit section: Checking permissions"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Permissions of a file can be checked in octal form and/or alphabetic form with the command line tool <code>stat</code> </p> <div class="mw-highlight mw-highlight-lang-console mw-content-ltr" dir="ltr"><pre><span></span><span class="gp">[ torvalds ~ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%a %A"</span><span class="w"> </span>~/test/ <span class="go">1770 drwxrwx--T</span> </pre></div> <div class="mw-heading mw-heading3"><h3 id="SUID">SUID</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=8" title="Edit section: SUID"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>4701</b> on an executable file owned by 'root' and the group 'root' </p><p>A user named 'thompson' attempts to execute the file. The executable permission for all users is set (the '1') so 'thompson' can execute the file. The file owner is 'root' and the SUID permission is set (the '4') - so the file is executed as 'root'. </p><p>The reason an executable would be run as 'root' is so that it can modify specific files that the user would not normally be allowed to, without giving the user full root access. </p><p> A default use of this can be seen with the <code>/usr/bin/passwd</code> binary file. <code>/usr/bin/passwd</code> needs to modify <code>/etc/passwd</code> and <code>/etc/shadow</code> which store account information and password hashes for all users, and these can only be modified by the user 'root'.</p><div class="mw-highlight mw-highlight-lang-console mw-content-ltr" dir="ltr"><pre><span></span><span class="gp">[ thompson ~ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%a %U:%G %n"</span><span class="w"> </span>/usr/bin/passwd <span class="go">4701 root:root /usr/bin/passwd</span> <span class="gp">[ thompson ~ ] $ </span>passwd <span class="go">passwd: Changing password for thompson</span> </pre></div> <p>The owner of the process is not the user running the executable file but the owner of the executable file </p> <div class="mw-heading mw-heading3"><h3 id="SGID">SGID</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=9" title="Edit section: SGID"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>2770</b> on a directory named 'music' owned by the user 'root' and the group 'engineers' </p><p>A user named 'torvalds' who belongs primarily to the group 'torvalds' but secondarily to the group 'engineers' makes a directory named 'electronic' under the directory named 'music'. The group ownership of the new directory named 'electronic' inherits 'engineers.' This is the same when making a new <i>file</i> named 'imagine.txt' </p><p>Without SGID the group ownership of the new directory/file would have been 'torvalds' as that is the primary group of user 'torvalds'. </p> <div class="mw-highlight mw-highlight-lang-console mw-content-ltr" dir="ltr"><pre><span></span><span class="gp">[ torvalds ~ ] $ </span>groups<span class="w"> </span>torvalds <span class="go">torvalds : torvalds engineers</span> <span class="gp">[ torvalds ~ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%a %U:%G %n"</span><span class="w"> </span>./music/ <span class="go">2770 root:engineers ./music/</span> <span class="gp">[ torvalds ~ ] $ </span>mkdir<span class="w"> </span>./music/electronic <span class="gp">[ torvalds ~ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%U:%G %n"</span><span class="w"> </span>./music/electronic/ <span class="go">torvalds:engineers ./music/electronic/</span> <span class="gp">[ torvalds ~ ] $ </span><span class="nb">echo</span><span class="w"> </span><span class="s1">'NEW FILE'</span><span class="w"> </span>><span class="w"> </span>./music/imagine.txt <span class="gp">[ torvalds ~ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%U:%G %n"</span><span class="w"> </span>./music/imagine.txt <span class="go">torvalds:engineers ./music/imagine.txt</span> <span class="gp">[ torvalds ~ ] $ </span>touch<span class="w"> </span>~/test <span class="gp">[ torvalds ~ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%U:%G %n"</span><span class="w"> </span>~/test <span class="go">torvalds:torvalds ~/test</span> </pre></div> <div class="mw-heading mw-heading3"><h3 id="Sticky_bit">Sticky bit</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=10" title="Edit section: Sticky bit"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Sticky_bit" title="Sticky bit">Sticky bit</a></div> <p><b>1770</b> on a directory named 'videogames' owned by the user 'torvalds' and the group 'engineers'. </p><p>A user named 'torvalds' creates a file named 'tekken' under the directory named 'videogames'. A user named 'wozniak', who is also part of the group 'engineers', attempts to delete the file named 'tekken' but he cannot, since he is not the owner. </p><p>Without sticky bit, 'wozniak' could have deleted the file, because the directory named 'videogames' allows read and write by 'engineers'. A default use of this can be seen at the <code>/tmp</code> folder. </p> <div class="mw-highlight mw-highlight-lang-console mw-content-ltr" dir="ltr"><pre><span></span><span class="gp">[ torvalds /home/shared/ ] $ </span>groups<span class="w"> </span>torvalds <span class="go">torvalds : torvalds engineers</span> <span class="gp">[ torvalds /home/shared/ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%a %U:%G %n"</span><span class="w"> </span>./videogames/ <span class="go">1770 torvalds:engineers ./videogames/</span> <span class="gp">[ torvalds /home/shared/ ] $ </span><span class="nb">echo</span><span class="w"> </span><span class="s1">'NEW FILE'</span><span class="w"> </span>><span class="w"> </span>videogames/tekken <span class="gp">[ torvalds /home/shared/ ] $ </span>su<span class="w"> </span>-<span class="w"> </span>wozniak <span class="go">Password:</span> <span class="gp">[ wozniak ~/ ] $ </span>groups<span class="w"> </span>wozniak <span class="go">wozniak : wozniak engineers</span> <span class="gp">[ wozniak ~/ ] $ </span><span class="nb">cd</span><span class="w"> </span>/home/shared/videogames <span class="gp">[ wozniak /home/shared/videogames/ ] $ </span>rm<span class="w"> </span>tekken <span class="go">rm: cannot remove ‘tekken’: Operation not permitted</span> </pre></div> <div class="mw-heading mw-heading3"><h3 id="Sticky_bit_with_SGID">Sticky bit with SGID</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=11" title="Edit section: Sticky bit with SGID"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><b>3171</b> on a directory named 'blog' owned by the group 'engineers' and the user 'root' </p><p>A user named 'torvalds' who belongs primarily to the group 'torvalds' but secondarily to the group 'engineers' creates a file or directory named 'thoughts' inside the directory 'blog'. A user named 'wozniak' who also belongs to the group 'engineers' cannot delete, rename, or move the file or directory named 'thoughts', because he is not the owner and the sticky bit is set. However, if 'thoughts' is a file, then 'wozniak' can edit it. </p> <p><b>Sticky bit has the final decision.</b> If sticky bit and SGID had not been set, the user 'wozniak' could rename, move, or delete the file named 'thoughts' because the directory named 'blog' allows read and write by group, and wozniak belongs to the group, and the default 0002 <a href="/wiki/Umask" title="Umask">umask</a> allows new files to be edited by group. Sticky bit and SGID could be combined with something such as a read-only umask or an append only attribute.</p><div class="mw-highlight mw-highlight-lang-console mw-content-ltr" dir="ltr"><pre><span></span><span class="gp">[ torvalds /home/shared/ ] $ </span>groups<span class="w"> </span>torvalds <span class="go">torvalds : torvalds engineers</span> <span class="gp">[ torvalds /home/shared/ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%a %U:%G %n"</span><span class="w"> </span>./blog/ <span class="go">3171 root:engineers ./blog/</span> <span class="gp">[ torvalds /home/shared/ ] $ </span><span class="nb">echo</span><span class="w"> </span><span class="s1">'NEW FILE'</span><span class="w"> </span>><span class="w"> </span>./blog/thoughts <span class="gp">[ torvalds /home/shared/ ] $ </span>su<span class="w"> </span>-<span class="w"> </span>wozniak <span class="go">Password:</span> <span class="gp">[ wozniak ~/ ] $ </span><span class="nb">cd</span><span class="w"> </span>/home/shared/blog <span class="gp">[ wozniak /home/shared/blog/ ] $ </span>groups<span class="w"> </span>wozniak <span class="go">wozniak : wozniak engineers</span> <span class="gp">[ wozniak /home/shared/blog/ ] $ </span>stat<span class="w"> </span>-c<span class="w"> </span><span class="s2">"%a %U:%G %n"</span><span class="w"> </span>./thoughts <span class="go">664 torvalds:engineers ./thoughts</span> <span class="gp">[ wozniak /home/shared/blog/ ] $ </span>rm<span class="w"> </span>thoughts <span class="go">rm: cannot remove ‘thoughts’: Operation not permitted</span> <span class="gp">[ wozniak /home/shared/blog/ ] $ </span>mv<span class="w"> </span>thoughts<span class="w"> </span>/home/wozniak/ <span class="go">mv: cannot move ‘thoughts’ to ‘/home/wozniak/thoughts’: Operation not permitted</span> <span class="gp">[ wozniak /home/shared/blog/ ] $ </span>mv<span class="w"> </span>thoughts<span class="w"> </span>pondering <span class="go">mv: cannot move ‘thoughts’ to ‘pondering’: Operation not permitted</span> <span class="gp">[ wozniak /home/shared/blog/ ] $ </span><span class="nb">echo</span><span class="w"> </span><span class="s1">'REWRITE!'</span><span class="w"> </span>><span class="w"> </span>thoughts <span class="gp">[ wozniak /home/shared/blog/ ] $ </span>cat<span class="w"> </span>thoughts <span class="go">REWRITE!</span> </pre></div> <div class="mw-heading mw-heading2"><h2 id="Security">Security</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=12" title="Edit section: Security"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Developers design and implement programs that use this bit on executables carefully in order to avoid security vulnerabilities including <a href="/wiki/Buffer_overrun" class="mw-redirect" title="Buffer overrun">buffer overruns</a> and <a href="/w/index.php?title=Path_injection&action=edit&redlink=1" class="new" title="Path injection (page does not exist)">path injection</a>. Successful buffer-overrun attacks on vulnerable applications allow the attacker to execute arbitrary code under the rights of the process exploited. In the event that a vulnerable process uses the <code>setuid</code> bit to run as <code>root</code>, the code will execute with root privileges, in effect giving the attacker root access to the system on which the vulnerable process is running. </p><p>Of particular importance in the case of a <code>setuid</code> process is the <a href="/wiki/Environment_(computing)" class="mw-redirect" title="Environment (computing)">environment</a> of the process. If the environment is not properly sanitized by a privileged process, its behavior can be changed by the unprivileged process that started it.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> For example, <a href="/wiki/GNU_libc" class="mw-redirect" title="GNU libc">GNU libc</a> was at one point vulnerable to an <a href="/wiki/Security_exploit" class="mw-redirect" title="Security exploit">exploit</a> using <code>setuid</code> and an environment variable that allowed executing code from untrusted <a href="/wiki/Shared_libraries" class="mw-redirect" title="Shared libraries">shared libraries</a>.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=13" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <code>setuid</code> bit was invented by <a href="/wiki/Dennis_Ritchie" title="Dennis Ritchie">Dennis Ritchie</a><sup id="cite_ref-reader_10-0" class="reference"><a href="#cite_note-reader-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> and included in <code><a href="/wiki/Su_(Unix)" title="Su (Unix)">su</a></code>.<sup id="cite_ref-reader_10-1" class="reference"><a href="#cite_note-reader-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> His employer, then <a href="/wiki/Bell_Telephone_Laboratories" class="mw-redirect" title="Bell Telephone Laboratories">Bell Telephone Laboratories</a>, applied for a patent in 1972; the patent was granted in 1979 as patent number <style data-mw-deduplicate="TemplateStyles:r1041539562">.mw-parser-output .citation{word-wrap:break-word}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}</style><span class="citation patent"><a rel="nofollow" class="external text" href="https://worldwide.espacenet.com/textdoc?DB=EPODOC&IDX=US4135240">US 4135240</a></span><span class="Z3988" title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Apatent&rft.number=4135240&rft.cc=US&rft.title="><span style="display: none;"> </span></span> "Protection of data file contents". The patent was later placed in the <a href="/wiki/Public_domain" title="Public domain">public domain</a>.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 22em;"> <ul><li><a href="/wiki/User_identifier" title="User identifier">User identifier</a></li> <li><a href="/wiki/Group_identifier" title="Group identifier">Group identifier</a></li> <li><a href="/wiki/Process_identifier" title="Process identifier">Process identifier</a></li> <li><code><a href="/wiki/Chmod" title="Chmod">chmod</a></code></li> <li><code><a href="/wiki/Sudo" title="Sudo">sudo</a></code></li> <li><a href="/wiki/Confused_deputy_problem" title="Confused deputy problem">Confused deputy problem</a></li> <li><a href="/wiki/PolicyKit" class="mw-redirect" title="PolicyKit">PolicyKit</a></li> <li><a href="/wiki/Unix_security" title="Unix security">Unix security</a></li> <li><a href="/wiki/Privilege_revocation_(computing)" title="Privilege revocation (computing)">Privilege revocation (computing)</a></li> <li><a href="/wiki/Privilege_separation" title="Privilege separation">Privilege separation</a></li></ul></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=15" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFvon_Hagen2010" class="citation book cs1">von Hagen, William (2010-05-13). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=rsSlrQLB8-gC&q=set%20user%20ID%20upon%20execution&pg=SA3-PA59"><i>Ubuntu Linux Bible</i></a>. pp. 3–59. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780470881804" title="Special:BookSources/9780470881804"><bdi>9780470881804</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Ubuntu+Linux+Bible&rft.pages=3-59&rft.date=2010-05-13&rft.isbn=9780470881804&rft.aulast=von+Hagen&rft.aufirst=William&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DrsSlrQLB8-gC%26q%3Dset%2520user%2520ID%2520upon%2520execution%26pg%3DSA3-PA59&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-oreilly-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-oreilly_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-oreilly_2-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-oreilly_2-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFrisch2009" class="citation book cs1">Frisch, Æleen (2009-02-09). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=uRW8V9QOL7YC&q=setuid&pg=PT375"><i>Essential system administration</i></a>. O'Reilly. p. 351. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780596550493" title="Special:BookSources/9780596550493"><bdi>9780596550493</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Essential+system+administration&rft.pages=351&rft.pub=O%27Reilly&rft.date=2009-02-09&rft.isbn=9780596550493&rft.aulast=Frisch&rft.aufirst=%C3%86leen&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DuRW8V9QOL7YC%26q%3Dsetuid%26pg%3DPT375&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBillimoria2018" class="citation book cs1">Billimoria, Kaiwan N. (2018). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=aOh1DwAAQBAJ&pg=PA250"><i>Hands-On System Programming with Linux: Explore Linux system programming interfaces, theory, and practice</i></a>. Packt Publishing Ltd. p. 250. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-78899-674-7" title="Special:BookSources/978-1-78899-674-7"><bdi>978-1-78899-674-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Hands-On+System+Programming+with+Linux%3A+Explore+Linux+system+programming+interfaces%2C+theory%2C+and+practice&rft.pages=250&rft.pub=Packt+Publishing+Ltd&rft.date=2018&rft.isbn=978-1-78899-674-7&rft.aulast=Billimoria&rft.aufirst=Kaiwan+N.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DaOh1DwAAQBAJ%26pg%3DPA250&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.faqs.org/faqs/unix-faq/faq/part4/section-7.html">"Unix - Frequently Asked Questions"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Unix+-+Frequently+Asked+Questions&rft_id=http%3A%2F%2Fwww.faqs.org%2Ffaqs%2Funix-faq%2Ffaq%2Fpart4%2Fsection-7.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.gnu.org/software/coreutils/manual/html_node/Directory-Setuid-and-Setgid.html#Directories-and-the-Set_002dUser_002dID-and-Set_002dGroup_002dID-Bits">"27.5 Directories and the Set-User-ID and Set-Group-ID Bits"</a>. <i>GNU Coreutils 9.1</i>. Free Software Foundation<span class="reference-accessdate">. Retrieved <span class="nowrap">13 December</span> 2022</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=GNU+Coreutils+9.1&rft.atitle=27.5+Directories+and+the+Set-User-ID+and+Set-Group-ID+Bits&rft_id=https%3A%2F%2Fwww.gnu.org%2Fsoftware%2Fcoreutils%2Fmanual%2Fhtml_node%2FDirectory-Setuid-and-Setgid.html%23Directories-and-the-Set_002dUser_002dID-and-Set_002dGroup_002dID-Bits&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.freebsd.org/cgi/man.cgi?query=chmod&apropos=0&sektion=0&manpath=FreeBSD+6.1-RELEASE&format=html">"chmod -- change file modes"</a>. <i>freebsd.org</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=freebsd.org&rft.atitle=chmod+--+change+file+modes&rft_id=http%3A%2F%2Fwww.freebsd.org%2Fcgi%2Fman.cgi%3Fquery%3Dchmod%26apropos%3D0%26sektion%3D0%26manpath%3DFreeBSD%2B6.1-RELEASE%26format%3Dhtml&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.freebsd.org/cgi/man.cgi?query=open&sektion=2">"open, openat -- open or create a file for reading, writing or executing"</a>. <i>freebsd.org</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=freebsd.org&rft.atitle=open%2C+openat+--+open+or+create+a+file+for+reading%2C+writing+or+executing&rft_id=https%3A%2F%2Fwww.freebsd.org%2Fcgi%2Fman.cgi%3Fquery%3Dopen%26sektion%3D2&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBrown2010" class="citation web cs1">Brown, Neil (November 23, 2010). <a rel="nofollow" class="external text" href="https://lwn.net/Articles/416494/">"Ghosts of Unix past, part 4: High-maintenance designs"</a>. <i>LWN.net</i><span class="reference-accessdate">. Retrieved <span class="nowrap">30 March</span> 2014</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=LWN.net&rft.atitle=Ghosts+of+Unix+past%2C+part+4%3A+High-maintenance+designs&rft.date=2010-11-23&rft.aulast=Brown&rft.aufirst=Neil&rft_id=https%3A%2F%2Flwn.net%2FArticles%2F416494%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFEdge2010" class="citation web cs1">Edge, Jake (October 27, 2010). <a rel="nofollow" class="external text" href="https://lwn.net/Articles/412048/">"Two glibc vulnerabilities"</a>. <i>LWN.net</i><span class="reference-accessdate">. Retrieved <span class="nowrap">30 March</span> 2014</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=LWN.net&rft.atitle=Two+glibc+vulnerabilities&rft.date=2010-10-27&rft.aulast=Edge&rft.aufirst=Jake&rft_id=https%3A%2F%2Flwn.net%2FArticles%2F412048%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-reader-10"><span class="mw-cite-backlink">^ <a href="#cite_ref-reader_10-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-reader_10-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMcIlroy1987" class="citation techreport cs1"><a href="/wiki/Doug_McIlroy" class="mw-redirect" title="Doug McIlroy">McIlroy, M. Douglas</a> (1987). <a rel="nofollow" class="external text" href="http://www.cs.dartmouth.edu/~doug/reader.pdf"><i>A Research Unix reader: annotated excerpts from the Programmer's Manual, 1971–1986</i></a> <span class="cs1-format">(PDF)</span> (Technical report). CSTR. Bell Labs. 139.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=report&rft.btitle=A+Research+Unix+reader%3A+annotated+excerpts+from+the+Programmer%27s+Manual%2C+1971%E2%80%931986&rft.series=CSTR&rft.pub=Bell+Labs&rft.date=1987&rft.aulast=McIlroy&rft.aufirst=M.+Douglas&rft_id=http%3A%2F%2Fwww.cs.dartmouth.edu%2F~doug%2Freader.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.textfiles.com/law/softpat.txt">"Summary of key software patents"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Summary+of+key+software+patents&rft_id=http%3A%2F%2Fwww.textfiles.com%2Flaw%2Fsoftpat.txt&rfr_id=info%3Asid%2Fen.wikipedia.org%3ASetuid" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Setuid&action=edit&section=16" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Chen, Hao; <a href="/wiki/David_A._Wagner" title="David A. Wagner">Wagner, David</a>; and Dean, Drew; <a rel="nofollow" class="external text" href="http://www.cs.berkeley.edu/~daw/papers/setuid-usenix02.pdf"><cite>Setuid Demystified</cite></a> (pdf)</li> <li>Tsafrir, Dan; <a href="/wiki/Dilma_Da_Silva" title="Dilma Da Silva">Da Silva, Dilma</a>; and Wagner, David; <a rel="nofollow" class="external text" href="http://www.eecs.berkeley.edu/~daw/papers/setuid-login08b.pdf"><cite>The Murky Issue of Changing Process Identity: Revising Setuid Demystified</cite></a> (pdf)</li> <li>Pollock, Wayne; <a rel="nofollow" class="external text" href="http://wpollock.com/AUnix1/FilePermissions.htm">Unix File and Directory <cite>Permissions and Modes</cite></a></li></ul> <!-- NewPP limit report Parsed by mw‐web.codfw.main‐f69cdc8f6‐rmmbn Cached time: 20241122144403 Cache expiry: 2592000 Reduced expiry: false Complications: [vary‐revision‐sha1, show‐toc] CPU time usage: 0.307 seconds Real time usage: 0.407 seconds Preprocessor visited node count: 1820/1000000 Post‐expand include size: 25278/2097152 bytes Template argument size: 2945/2097152 bytes Highest expansion depth: 12/100 Expensive parser function count: 12/500 Unstrip recursion depth: 1/20 Unstrip post‐expand size: 46043/5000000 bytes Lua time usage: 0.170/10.000 seconds Lua memory usage: 5531040/52428800 bytes Number of Wikibase entities loaded: 0/400 --> <!-- Transclusion expansion time report (%,ms,calls,template) 100.00% 371.145 1 -total 39.01% 144.797 1 Template:Reflist 25.12% 93.223 3 Template:Cite_book 18.71% 69.435 1 Template:Short_description 14.31% 53.117 1 Template:Cn 14.23% 52.814 2 Template:Fix 11.85% 43.969 2 Template:Pagetype 10.58% 39.286 4 Template:Category_handler 6.97% 25.870 7 Template:Cite_web 6.25% 23.184 1 Template:Redirect --> <!-- Saved in parser cache with key enwiki:pcache:idhash:1054629-0!canonical and timestamp 20241122144403 and revision id 1217859762. 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