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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=Fork+%28system+call%29" 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" 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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-Overview" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Overview"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Overview</span> </div> </a> <ul id="toc-Overview-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">2</span> <span>History</span> </div> </a> <ul id="toc-History-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Communication" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Communication"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Communication</span> </div> </a> <ul id="toc-Communication-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Variants" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Variants"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Variants</span> </div> </a> <button aria-controls="toc-Variants-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 Variants subsection</span> </button> <ul id="toc-Variants-sublist" class="vector-toc-list"> <li id="toc-Vfork" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Vfork"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Vfork</span> </div> </a> <ul id="toc-Vfork-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Rfork" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Rfork"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Rfork</span> </div> </a> <ul id="toc-Rfork-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Clone" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Clone"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.3</span> <span>Clone</span> </div> </a> <ul id="toc-Clone-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Forking_in_other_operating_systems" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Forking_in_other_operating_systems"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Forking in other operating systems</span> </div> </a> <ul id="toc-Forking_in_other_operating_systems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Application_usage" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Application_usage"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Application usage</span> </div> </a> <ul id="toc-Application_usage-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">7</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">8</span> <span>References</span> </div> </a> <ul id="toc-References-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">fork (system call)</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 19 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-19" 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">19 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/Fork_(Unix)" title="Fork (Unix) – Catalan" lang="ca" hreflang="ca" data-title="Fork (Unix)" 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/Fork_(syst%C3%A9mov%C3%A9_vol%C3%A1n%C3%AD)" title="Fork (systémové volání) – Czech" lang="cs" hreflang="cs" data-title="Fork (systémové volání)" 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/Fork_(Unix)" title="Fork (Unix) – German" lang="de" hreflang="de" data-title="Fork (Unix)" 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/Bifurcaci%C3%B3n_(sistema_operativo)" title="Bifurcación (sistema operativo) – Spanish" lang="es" hreflang="es" data-title="Bifurcación (sistema operativo)" 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/Adarkatze_(sistema_eragileak)" title="Adarkatze (sistema eragileak) – Basque" lang="eu" hreflang="eu" data-title="Adarkatze (sistema eragileak)" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/Fork_(%D9%81%D8%B1%D8%A7%D8%AE%D9%88%D8%A7%D9%86_%D8%B3%DB%8C%D8%B3%D8%AA%D9%85%DB%8C)" title="Fork (فراخوان سیستمی) – Persian" lang="fa" hreflang="fa" data-title="Fork (فراخوان سیستمی)" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Fork_(programmation)" title="Fork (programmation) – French" lang="fr" hreflang="fr" data-title="Fork (programmation)" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%ED%8F%AC%ED%81%AC_(%EC%8B%9C%EC%8A%A4%ED%85%9C_%ED%98%B8%EC%B6%9C)" title="포크 (시스템 호출) – Korean" lang="ko" hreflang="ko" data-title="포크 (시스템 호출)" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Fork_(programmazione)" title="Fork (programmazione) – Italian" lang="it" hreflang="it" data-title="Fork (programmazione)" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/Fork_(%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B8%D0%B9%D0%BD_%D0%B4%D1%83%D1%83%D0%B4%D0%B0%D0%BB%D1%82)" title="Fork (системийн дуудалт) – Mongolian" lang="mn" hreflang="mn" data-title="Fork (системийн дуудалт)" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Fork_(informatica)" title="Fork (informatica) – Dutch" lang="nl" hreflang="nl" data-title="Fork (informatica)" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/Fork" title="Fork – Japanese" lang="ja" hreflang="ja" data-title="Fork" 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-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Fork_(Unix)" title="Fork (Unix) – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Fork (Unix)" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Fork_(Unix)" title="Fork (Unix) – Polish" lang="pl" hreflang="pl" data-title="Fork (Unix)" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/Fork" title="Fork – Russian" lang="ru" hreflang="ru" data-title="Fork" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Fork_(systemanrop)" title="Fork (systemanrop) – Swedish" lang="sv" hreflang="sv" data-title="Fork (systemanrop)" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/Fork_(%D1%81%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%BD%D0%B8%D0%B9_%D0%B2%D0%B8%D0%BA%D0%BB%D0%B8%D0%BA)" title="Fork (системний виклик) – Ukrainian" lang="uk" hreflang="uk" data-title="Fork (системний виклик)" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Fork_(l%E1%BB%9Di_g%E1%BB%8Di_h%E1%BB%87_th%E1%BB%91ng)" 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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">In computing, an operation whereby a process creates a copy of itself</div> <p>In <a href="/wiki/Computing" title="Computing">computing</a>, particularly in the context of the <a href="/wiki/Unix" title="Unix">Unix</a> operating system and <a href="/wiki/Unix-like" title="Unix-like">its workalikes</a>, <b>fork</b> is an operation whereby a <a href="/wiki/Computer_process" class="mw-redirect" title="Computer process">process</a> creates a copy of itself. It is an interface which is required for compliance with the <a href="/wiki/POSIX" title="POSIX">POSIX</a> and <a href="/wiki/Single_UNIX_Specification" title="Single UNIX Specification">Single UNIX Specification</a> standards. It is usually implemented as a <a href="/wiki/C_standard_library" title="C standard library">C standard library</a> <a href="/wiki/Wrapper_library" title="Wrapper library">wrapper</a> to the fork, clone, or other <a href="/wiki/System_call" title="System call">system calls</a> of the <a href="/wiki/Kernel_(operating_system)" title="Kernel (operating system)">kernel</a>. Fork is the primary method of process creation on Unix-like operating systems. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Overview">Overview</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=1" title="Edit section: Overview"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In multitasking operating systems, processes (running programs) need a way to create new processes, e.g. to run other programs. Fork and its variants are typically the only way of doing so in Unix-like systems. For a process to start the execution of a different program, it first forks to create a copy of itself. Then, the copy, called the "<a href="/wiki/Child_process" title="Child process">child process</a>", calls the <a href="/wiki/Exec_(system_call)" title="Exec (system call)">exec</a> system call to overlay itself with the other program: it ceases execution of its former program in favor of the other. </p><p>The fork operation creates a separate <a href="/wiki/Address_space" title="Address space">address space</a> for the child. The child process has an exact copy of all the memory segments of the parent process. In modern UNIX variants that follow the <a href="/wiki/Virtual_memory" title="Virtual memory">virtual memory</a> model from <a href="/wiki/SunOS" title="SunOS">SunOS</a>-4.0, <a href="/wiki/Copy-on-write" title="Copy-on-write">copy-on-write</a> semantics are implemented and the physical memory need not be actually copied. Instead, <a href="/wiki/Virtual_memory_pages" class="mw-redirect" title="Virtual memory pages">virtual memory pages</a> in both processes may refer to the same pages of <a href="/wiki/Physical_memory" class="mw-redirect" title="Physical memory">physical memory</a> until one of them writes to such a page: then it is copied. This optimization is important in the common case where fork is used in conjunction with exec to execute a new program: typically, the child process performs only a small set of actions before it ceases execution of its program in favour of the program to be started, and it requires very few, if any, of its parent's <a href="/wiki/Data_structure" title="Data structure">data structures</a>. </p><p>When a process calls fork, it is deemed the <a href="/wiki/Parent_process" title="Parent process">parent process</a> and the newly created process is its child. After the fork, both processes not only run the same program, but they resume execution as though both had called the system call. They can then inspect the call's <a href="/wiki/Return_value" class="mw-redirect" title="Return value">return value</a> to determine their status, child or parent, and act accordingly. </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=Fork_(system_call)&action=edit&section=2" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>One of the earliest references to a fork concept appeared in <i>A Multiprocessor System Design</i> by <a href="/wiki/Melvin_Conway" title="Melvin Conway">Melvin Conway</a>, published in 1962.<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> Conway's paper motivated the implementation by <a href="/wiki/L._Peter_Deutsch" title="L. Peter Deutsch">L. Peter Deutsch</a> of fork in the <a href="/wiki/Project_Genie" title="Project Genie">GENIE time-sharing system</a>, where the concept was borrowed by <a href="/wiki/Ken_Thompson" title="Ken Thompson">Ken Thompson</a> for its earliest appearance<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> in <a href="/wiki/Research_Unix" title="Research Unix">Research Unix</a>.<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><sup id="cite_ref-Ritchie_4-0" class="reference"><a href="#cite_note-Ritchie-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Fork later became a standard interface in <a href="/wiki/POSIX" title="POSIX">POSIX</a>.<sup id="cite_ref-posix_5-0" class="reference"><a href="#cite_note-posix-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Communication">Communication</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=3" title="Edit section: Communication"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The child process starts off with a copy of its parent's <a href="/wiki/File_descriptor" title="File descriptor">file descriptors</a>.<sup id="cite_ref-posix_5-1" class="reference"><a href="#cite_note-posix-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> For interprocess communication, the parent process will often create one or several <a href="/wiki/Pipe_(computer_science)" class="mw-redirect" title="Pipe (computer science)">pipes</a>, and then after forking the processes will close the ends of the pipes that they do not need.<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> </p> <div class="mw-heading mw-heading2"><h2 id="Variants">Variants</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=4" title="Edit section: Variants"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Vfork">Vfork</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=5" title="Edit section: Vfork"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Vfork is a variant of fork with the same <a href="/wiki/Calling_convention" title="Calling convention">calling convention</a> and much the same semantics, but only to be used in restricted situations. It originated in the <a href="/wiki/Berkeley_Software_Distribution" title="Berkeley Software Distribution">3BSD</a> version of Unix,<sup id="cite_ref-man|2|vfork|Linux_7-0" class="reference"><a href="#cite_note-man|2|vfork|Linux-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-netbsd-vfork_8-0" class="reference"><a href="#cite_note-netbsd-vfork-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><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> the first Unix to support virtual memory. It was standardized by POSIX, which permitted vfork to have exactly the same behavior as fork, but was marked obsolescent in the 2004 edition<sup id="cite_ref-posix-vfork_10-0" class="reference"><a href="#cite_note-posix-vfork-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> and was replaced by <a href="/wiki/Spawn_(computing)#POSIX_spawn_functions" title="Spawn (computing)">posix_spawn</a>() (which is typically implemented via vfork) in subsequent editions. </p><p>When a vfork system call is issued, the parent process will be suspended until the child process has either completed execution or been replaced with a new executable image via one of the "<a href="/wiki/Exec_(computing)" class="mw-redirect" title="Exec (computing)">exec</a>" family of system calls. The child borrows the <a href="/wiki/Memory_management_unit" title="Memory management unit">memory management unit</a> setup from the parent and memory pages are shared among the parent and child process with no copying done, and in particular with no <a href="/wiki/Copy-on-write" title="Copy-on-write">copy-on-write</a> semantics;<sup id="cite_ref-posix-vfork_10-1" class="reference"><a href="#cite_note-posix-vfork-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> hence, if the child process makes a modification in any of the shared pages, no new page will be created and the modified pages are visible to the parent process too. Since there is absolutely no page copying involved (consuming additional memory), this technique is an optimization over plain fork in full-copy environments when used with exec. In POSIX, using vfork for any purpose except as a prelude to an immediate call to a function from the exec family (and a select few other operations) gives rise to <a href="/wiki/Undefined_behavior" title="Undefined behavior">undefined behavior</a>.<sup id="cite_ref-posix-vfork_10-2" class="reference"><a href="#cite_note-posix-vfork-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> As with vfork, the child borrows data structures rather than copying them. vfork is still faster than a fork that uses copy on write semantics. </p><p><a href="/wiki/UNIX_System_V" title="UNIX System V">System V</a> did not support this function call before System VR4 was introduced,<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. (May 2015)">citation needed</span></a></i>]</sup> because the memory sharing that it causes is error-prone: </p> <style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style><blockquote class="templatequote"><p><i>Vfork</i> does not copy page tables so it is faster than the System V <i>fork</i> implementation. But the child process executes in the same physical address space as the parent process (until an <i>exec</i> or <i>exit</i>) and can thus overwrite the parent's data and stack. A dangerous situation could arise if a programmer uses <i>vfork</i> incorrectly, so the onus for calling <i>vfork</i> lies with the programmer. The difference between the System V approach and the BSD approach is philosophical: Should the kernel hide idiosyncrasies of its implementation from users, or should it allow sophisticated users the opportunity to take advantage of the implementation to do a logical function more efficiently?</p><div class="templatequotecite">— <cite>Maurice J. Bach<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></cite></div></blockquote> <p>Similarly, the Linux man page for vfork strongly discourages its use:<sup id="cite_ref-man|2|vfork|Linux_7-1" class="reference"><a href="#cite_note-man|2|vfork|Linux-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability"><span title="quote not in source (November 2019)">failed verification</span></a></i>]</sup><sup class="noprint selfreference">[<i><a href="/wiki/Talk:Fork_(system_call)#unfortunate,_etc" title="Talk:Fork (system call)">discuss</a></i>]</sup> </p> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1244412712"><blockquote class="templatequote"><p>It is rather unfortunate that Linux revived this specter from the past. The BSD man page states: "This system call will be eliminated when proper system sharing mechanisms are implemented. Users should not depend on the memory sharing semantics of vfork() as it will, in that case, be made synonymous to fork(2)."</p></blockquote> <p>Other problems with <style data-mw-deduplicate="TemplateStyles:r886049734">.mw-parser-output .monospaced{font-family:monospace,monospace}</style><span class="monospaced">vfork</span> include <a href="/wiki/Deadlock_(computer_science)" title="Deadlock (computer science)">deadlocks</a> that might occur in <a href="/wiki/Multi-threaded" class="mw-redirect" title="Multi-threaded">multithreaded</a> programs due to interactions with <a href="/wiki/Dynamic_linking" class="mw-redirect" title="Dynamic linking">dynamic linking</a>.<sup id="cite_ref-oracle_12-0" class="reference"><a href="#cite_note-oracle-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> As a replacement for the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">vfork</span> interface, POSIX introduced the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">posix_spawn</span> family of functions that combine the actions of fork and exec. These functions may be implemented as library routines in terms of <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span>, as is done in Linux,<sup id="cite_ref-oracle_12-1" class="reference"><a href="#cite_note-oracle-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> or in terms of <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">vfork</span> for better performance, as is done in Solaris,<sup id="cite_ref-oracle_12-2" class="reference"><a href="#cite_note-oracle-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> but the POSIX specification notes that they were "designed as <a href="/wiki/System_call" title="System call">kernel operations</a>", especially for operating systems running on constrained hardware and <a href="/wiki/Real-time_computing" title="Real-time computing">real-time systems</a>.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p><p>While the 4.4BSD implementation got rid of the vfork implementation, causing vfork to have the same behavior as fork, it was later reinstated in the <a href="/wiki/NetBSD" title="NetBSD">NetBSD</a> operating system for performance reasons.<sup id="cite_ref-netbsd-vfork_8-1" class="reference"><a href="#cite_note-netbsd-vfork-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Some embedded operating systems such as <a href="/wiki/UClinux" class="mw-redirect" title="UClinux">uClinux</a> omit fork and only implement vfork, because they need to operate on devices where copy-on-write is impossible to implement due to lack of a memory management unit. </p> <div class="mw-heading mw-heading3"><h3 id="Rfork">Rfork</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=6" title="Edit section: Rfork"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Plan_9_from_Bell_Labs" title="Plan 9 from Bell Labs">Plan 9</a> operating system, created by the designers of Unix, includes fork but also a variant called "rfork" that permits fine-grained sharing of resources between parent and child processes, including the address space (except for a <a href="/wiki/Call_stack" title="Call stack">stack</a> segment, which is unique to each process), <a href="/wiki/Environment_variable" title="Environment variable">environment variables</a> and the filesystem namespace;<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> this makes it a unified interface for the creation of both processes and <a href="/wiki/Thread_(computer_science)" class="mw-redirect" title="Thread (computer science)">threads</a> within them.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Both <a href="/wiki/FreeBSD" title="FreeBSD">FreeBSD</a><sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> and <a href="/wiki/IRIX" title="IRIX">IRIX</a> adopted the rfork system call from Plan 9, the latter renaming it "sproc".<sup id="cite_ref-opensources_18-0" class="reference"><a href="#cite_note-opensources-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p><p><span class="anchor" id="Linux_clone_syscall"></span> </p> <div class="mw-heading mw-heading3"><h3 id="Clone">Clone</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=7" title="Edit section: Clone"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><code>clone</code> is a system call in the <a href="/wiki/Linux_kernel" title="Linux kernel">Linux kernel</a> that creates a child process that may share parts of its execution <a href="/wiki/Context_(computing)" title="Context (computing)">context</a> with the parent. Like FreeBSD's rfork and IRIX's sproc, Linux's clone was inspired by Plan 9's rfork and can be used to implement threads (though application programmers will typically use a higher-level interface such as <a href="/wiki/Pthreads" title="Pthreads">pthreads</a>, implemented on top of clone). The "separate stacks" feature from Plan 9 and IRIX has been omitted because (according to <a href="/wiki/Linus_Torvalds" title="Linus Torvalds">Linus Torvalds</a>) it causes too much overhead.<sup id="cite_ref-opensources_18-1" class="reference"><a href="#cite_note-opensources-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Forking_in_other_operating_systems">Forking in other operating systems</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=8" title="Edit section: Forking in other operating systems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-One_source plainlinks metadata ambox ambox-content ambox-one_source" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>relies largely or entirely on a <a href="/wiki/Wikipedia:Articles_with_a_single_source" title="Wikipedia:Articles with a single source">single source</a></b>.<span class="hide-when-compact"> Relevant discussion may be found on the <a href="/wiki/Talk:Fork_(system_call)##" title="Talk:Fork (system call)">talk page</a>. Please help <a class="external text" href="https://en.wikipedia.org/w/index.php?title=Fork_(system_call)&action=edit">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">introducing citations to additional sources</a>.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Fork%22+system+call">"Fork" system call</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Fork%22+system+call+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Fork%22+system+call&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Fork%22+system+call+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Fork%22+system+call">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Fork%22+system+call&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">February 2015</span>)</i></span></div></td></tr></tbody></table> <p>In the original design of the <a href="/wiki/OpenVMS" title="OpenVMS">VMS</a> operating system (1977), a copy operation with subsequent mutation of the content of a few specific addresses for the new process as in forking was considered risky.<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. (October 2013)">citation needed</span></a></i>]</sup> Errors in the current process state may be copied to a child process. Here, the metaphor of process spawning is used: each component of the memory layout of the new process is newly constructed from scratch. The <a href="/wiki/Spawn_(computing)" title="Spawn (computing)">spawn</a> metaphor was later adopted in Microsoft operating systems (1993). </p><p>The POSIX-compatibility component of <a href="/wiki/VM/CMS" class="mw-redirect" title="VM/CMS">VM/CMS</a> (OpenExtensions) provides a very limited implementation of fork, in which the parent is suspended while the child executes, and the child and the parent share the same address space.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> This is essentially a <i>vfork</i> labelled as a <i>fork</i>. (This applies to the CMS guest operating system only; other VM guest operating systems, such as Linux, provide standard fork functionality.) </p> <div class="mw-heading mw-heading2"><h2 id="Application_usage">Application usage</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Fork_(system_call)&action=edit&section=9" title="Edit section: Application usage"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The following variant of the <a href="/wiki/%22Hello,_World!%22_program" title=""Hello, World!" program">"Hello, World!" program</a> demonstrates the mechanics of the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span> system call in the <a href="/wiki/C_(programming_language)" title="C (programming language)">C</a> programming language. The program forks into two processes, each deciding what functionality they perform based on the return value of the fork system call. <a href="/wiki/Boilerplate_code" title="Boilerplate code">Boilerplate code</a> such as <a href="/wiki/Header_file" class="mw-redirect" title="Header file">header inclusions</a> has been omitted. </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">(</span><span class="kt">void</span><span class="p">)</span> <span class="p">{</span> <span class="w"> </span><span class="kt">pid_t</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fork</span><span class="p">();</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">-1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="n">perror</span><span class="p">(</span><span class="s">"fork failed"</span><span class="p">);</span> <span class="w"> </span><span class="n">exit</span><span class="p">(</span><span class="n">EXIT_FAILURE</span><span class="p">);</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="n">printf</span><span class="p">(</span><span class="s">"Hello from the child process!</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span> <span class="w"> </span><span class="n">_exit</span><span class="p">(</span><span class="n">EXIT_SUCCESS</span><span class="p">);</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">status</span><span class="p">;</span> <span class="w"> </span><span class="p">(</span><span class="kt">void</span><span class="p">)</span><span class="n">waitpid</span><span class="p">(</span><span class="n">pid</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">status</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">EXIT_SUCCESS</span><span class="p">;</span> <span class="p">}</span> </pre></div> <p>What follows is a dissection of this program. </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="kt">pid_t</span><span class="w"> </span><span class="n">pid</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fork</span><span class="p">();</span> </pre></div> <p>The first statement in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">main</span> calls the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span> system call to split execution into two processes. The return value of <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span> is recorded in a variable of type <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">pid_t</span>, which is the POSIX type for process identifiers (PIDs). </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">-1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="n">perror</span><span class="p">(</span><span class="s">"fork failed"</span><span class="p">);</span> <span class="w"> </span><span class="n">exit</span><span class="p">(</span><span class="n">EXIT_FAILURE</span><span class="p">);</span> <span class="w"> </span><span class="p">}</span> </pre></div> <p>Minus one indicates an error in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span>: no new process was created, so an error message is printed. </p><p>If <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span> was successful, then there are now two processes, both executing the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">main</span> function from the point where <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span> has returned. To make the processes perform different tasks, the program must <a href="/wiki/Branch_(computer_science)" title="Branch (computer science)">branch</a> on the return value of <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span> to determine whether it is executing as the <i>child</i> process or the <i>parent</i> process. </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">pid</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="n">printf</span><span class="p">(</span><span class="s">"Hello from the child process!</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span> <span class="w"> </span><span class="n">_exit</span><span class="p">(</span><span class="n">EXIT_SUCCESS</span><span class="p">);</span> <span class="w"> </span><span class="p">}</span> </pre></div> <p>In the child process, the return value appears as zero (which is an invalid process identifier). The child process prints the desired greeting message, then exits. (For technical reasons, the POSIX <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">_exit</span> function must be used here instead of the C standard <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">exit</span> function.) </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">status</span><span class="p">;</span> <span class="w"> </span><span class="p">(</span><span class="kt">void</span><span class="p">)</span><span class="n">waitpid</span><span class="p">(</span><span class="n">pid</span><span class="p">,</span><span class="w"> </span><span class="o">&</span><span class="n">status</span><span class="p">,</span><span class="w"> </span><span class="mi">0</span><span class="p">);</span> <span class="w"> </span><span class="p">}</span> </pre></div> <p>The other process, the parent, receives from <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">fork</span> the process identifier of the child, which is always a positive number. The parent process passes this identifier to the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">waitpid</span> system call to suspend execution until the child has exited. When this has happened, the parent resumes execution and exits by means of the <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">return</span> statement. </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=Fork_(system_call)&action=edit&section=10" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Fork_bomb" title="Fork bomb">Fork bomb</a></li> <li><a href="/wiki/Fork%E2%80%93exec" title="Fork–exec">Fork–exec</a></li> <li><a href="/wiki/Exit_(system_call)" title="Exit (system call)">exit (system call)</a></li> <li><a href="/wiki/Spawn_(computing)" title="Spawn (computing)">spawn (computing)</a></li> <li><a href="/wiki/Wait_(system_call)" title="Wait (system call)">wait (system call)</a></li></ul> <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=Fork_(system_call)&action=edit&section=11" 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="CITEREFNyman2016" class="citation journal cs1">Nyman, Linus (25 August 2016). "Notes on the History of Fork and Join". <i>IEEE Annals of the History of Computing</i>. <b>38</b> (3): 84–87. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2FMAHC.2016.34">10.1109/MAHC.2016.34</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=IEEE+Annals+of+the+History+of+Computing&rft.atitle=Notes+on+the+History+of+Fork+and+Join&rft.volume=38&rft.issue=3&rft.pages=84-87&rft.date=2016-08-25&rft_id=info%3Adoi%2F10.1109%2FMAHC.2016.34&rft.aulast=Nyman&rft.aufirst=Linus&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</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://github.com/dspinellis/unix-history-repo/blob/Research-PDP7-Snapshot-Development/s3.s#L43-L70">"s3.s from Research UNIX"</a>. <i>GitHub</i>. 1970.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=GitHub&rft.atitle=s3.s+from+Research+UNIX&rft.date=1970&rft_id=https%3A%2F%2Fgithub.com%2Fdspinellis%2Funix-history-repo%2Fblob%2FResearch-PDP7-Snapshot-Development%2Fs3.s%23L43-L70&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" 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="CITEREFKen_Thompson_and_Dennis_Ritchie1971" class="citation encyclopaedia cs1"><a href="/wiki/Ken_Thompson" title="Ken Thompson">Ken Thompson</a> and <a href="/wiki/Dennis_Ritchie" title="Dennis Ritchie">Dennis Ritchie</a> (3 November 1971). <a rel="nofollow" class="external text" href="https://www.bell-labs.com/usr/dmr/www/pdfs/man21.pdf">"SYS FORK (II)"</a> <span class="cs1-format">(PDF)</span>. <i>UNIX Programmer's Manual</i>. <a href="/wiki/Bell_Labs" title="Bell Labs">Bell Laboratories</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=SYS+FORK+%28II%29&rft.btitle=UNIX+Programmer%27s+Manual&rft.pub=Bell+Laboratories&rft.date=1971-11-03&rft.au=Ken+Thompson+and+Dennis+Ritchie&rft_id=https%3A%2F%2Fwww.bell-labs.com%2Fusr%2Fdmr%2Fwww%2Fpdfs%2Fman21.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> <li id="cite_note-Ritchie-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-Ritchie_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRitchieThompson1978" class="citation journal cs1"><a href="/wiki/Dennis_Ritchie" title="Dennis Ritchie">Ritchie, Dennis M.</a>; Thompson, Ken (July 1978). <a rel="nofollow" class="external text" href="https://www.bell-labs.com/usr/dmr/www/cacm.pdf">"The UNIX Time-Sharing System"</a> <span class="cs1-format">(PDF)</span>. <i>Bell System Tech. J</i>. <b>57</b> (6). AT&T: 1905–1929. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fj.1538-7305.1978.tb02136.x">10.1002/j.1538-7305.1978.tb02136.x</a><span class="reference-accessdate">. Retrieved <span class="nowrap">22 April</span> 2014</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Bell+System+Tech.+J.&rft.atitle=The+UNIX+Time-Sharing+System&rft.volume=57&rft.issue=6&rft.pages=1905-1929&rft.date=1978-07&rft_id=info%3Adoi%2F10.1002%2Fj.1538-7305.1978.tb02136.x&rft.aulast=Ritchie&rft.aufirst=Dennis+M.&rft.au=Thompson%2C+Ken&rft_id=https%3A%2F%2Fwww.bell-labs.com%2Fusr%2Fdmr%2Fwww%2Fcacm.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> <li id="cite_note-posix-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-posix_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-posix_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9799919799/functions/fork.html">fork</a></code></span> – System Interfaces Reference, <a href="/wiki/Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 4 from <a href="/wiki/The_Open_Group" title="The Open Group">The Open Group</a></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"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9799919799/functions/pipe.html">pipe</a></code></span> – System Interfaces Reference, <a href="/wiki/Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 4 from <a href="/wiki/The_Open_Group" title="The Open Group">The Open Group</a></span> </li> <li id="cite_note-man|2|vfork|Linux-7"><span class="mw-cite-backlink">^ <a href="#cite_ref-man|2|vfork|Linux_7-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-man|2|vfork|Linux_7-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://manned.org/vfork.2">vfork(2)</a></code></span> – <a href="/wiki/Linux" title="Linux">Linux</a> Programmer's <a href="/wiki/Man_page" title="Man page">Manual</a> – System Calls</span> </li> <li id="cite_note-netbsd-vfork-8"><span class="mw-cite-backlink">^ <a href="#cite_ref-netbsd-vfork_8-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-netbsd-vfork_8-1"><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 class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.netbsd.org/docs/kernel/vfork.html">"NetBSD Documentation: Why implement traditional vfork()"</a>. <i>NetBSD Project</i><span class="reference-accessdate">. Retrieved <span class="nowrap">16 October</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=NetBSD+Project&rft.atitle=NetBSD+Documentation%3A+Why+implement+traditional+vfork%28%29&rft_id=http%3A%2F%2Fwww.netbsd.org%2Fdocs%2Fkernel%2Fvfork.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" 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 class="citation encyclopaedia cs1">"vfork(2)". <i>UNIX Programmer's Manual, Virtual VAX-11 Version</i>. University of California, Berkeley. December 1979.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=vfork%282%29&rft.btitle=UNIX+Programmer%27s+Manual%2C+Virtual+VAX-11+Version&rft.pub=University+of+California%2C+Berkeley&rft.date=1979-12&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> <li id="cite_note-posix-vfork-10"><span class="mw-cite-backlink">^ <a href="#cite_ref-posix-vfork_10-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-posix-vfork_10-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-posix-vfork_10-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://www.opengroup.org/onlinepubs/009695399/functions/vfork.html">vfork</a></code></span> – System Interfaces Reference, <a href="/wiki/Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 3 from <a href="/wiki/The_Open_Group" title="The Open Group">The Open Group</a></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 id="CITEREFBach1986" class="citation book cs1">Bach, Maurice J. (1986). <i>The Design of The UNIX Operating System</i>. Prentice–Hall. pp. 291–292. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1986duos.book.....B">1986duos.book.....B</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Design+of+The+UNIX+Operating+System&rft.pages=291-292&rft.pub=Prentice%E2%80%93Hall&rft.date=1986&rft_id=info%3Abibcode%2F1986duos.book.....B&rft.aulast=Bach&rft.aufirst=Maurice+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> <li id="cite_note-oracle-12"><span class="mw-cite-backlink">^ <a href="#cite_ref-oracle_12-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-oracle_12-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-oracle_12-2"><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="CITEREFNakhimovsky2006" class="citation web cs1">Nakhimovsky, Greg (May 2006). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190922113430/https://www.oracle.com/technetwork/server-storage/solaris10/subprocess-136439.html">"Minimizing Memory Usage for Creating Application Subprocesses"</a>. <i>Oracle Technology Network</i>. <a href="/wiki/Oracle_Corporation" title="Oracle Corporation">Oracle Corporation</a>. Archived from <a rel="nofollow" class="external text" href="http://www.oracle.com/technetwork/server-storage/solaris10/subprocess-136439.html">the original</a> on Sep 22, 2019.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Oracle+Technology+Network&rft.atitle=Minimizing+Memory+Usage+for+Creating+Application+Subprocesses&rft.date=2006-05&rft.aulast=Nakhimovsky&rft.aufirst=Greg&rft_id=http%3A%2F%2Fwww.oracle.com%2Ftechnetwork%2Fserver-storage%2Fsolaris10%2Fsubprocess-136439.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><a href="https://sourceforge.net/p/schillix-on/schillix-on/ci/default/tree/usr/src/lib/libc/port/threads/spawn.c" class="extiw" title="sourceforge:p/schillix-on/schillix-on/ci/default/tree/usr/src/lib/libc/port/threads/spawn.c">The OpenSolaris posix_spawn() implementation</a></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9799919799/functions/posix_spawn.html">posix_spawn</a></code></span> – System Interfaces Reference, <a href="/wiki/Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 4 from <a href="/wiki/The_Open_Group" title="The Open Group">The Open Group</a></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://9p.io/magic/man2html/2/fork">fork(2)</a></code></span> – <a href="/wiki/Plan_9_from_Bell_Labs" title="Plan 9 from Bell Labs">Plan 9</a> Programmer's Manual, Volume 1</span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://9p.io/magic/man2html/2/intro">intro(2)</a></code></span> – <a href="/wiki/Plan_9_from_Bell_Labs" title="Plan 9 from Bell Labs">Plan 9</a> Programmer's Manual, Volume 1</span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><span class="plainlinksneverexpand"><code><a rel="nofollow" class="external text" href="https://www.freebsd.org/cgi/man.cgi?query=rfork&sektion=2">rfork(2)</a></code></span> – <a href="/wiki/FreeBSD" title="FreeBSD">FreeBSD</a> System Calls <a href="/wiki/Man_page" title="Man page">Manual</a></span> </li> <li id="cite_note-opensources-18"><span class="mw-cite-backlink">^ <a href="#cite_ref-opensources_18-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-opensources_18-1"><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="CITEREFTorvalds1999" class="citation encyclopaedia cs1">Torvalds, Linus (1999). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/isbn_9781565925823">"The Linux edge"</a></span>. <i>Open Sources: Voices from the Open Source Revolution</i>. O'Reilly. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-56592-582-3" title="Special:BookSources/978-1-56592-582-3"><bdi>978-1-56592-582-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+Linux+edge&rft.btitle=Open+Sources%3A+Voices+from+the+Open+Source+Revolution&rft.pub=O%27Reilly&rft.date=1999&rft.isbn=978-1-56592-582-3&rft.aulast=Torvalds&rft.aufirst=Linus&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fisbn_9781565925823&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</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-01.ibm.com/support/knowledgecenter/SSB27U_6.2.0/com.ibm.zvm.v620.dmsp0/hcsp0c0022.htm%23wq47?lang=en">"z/VM > z/VM 6.2.0 > Application Programming > z/VM V6R2 OpenExtensions POSIX Conformance Document > POSIX.1 Conformance Document > Section 3. Process Primitives > 3.1 Process Creation and Execution > 3.1.1 Process Creation"</a>. IBM<span class="reference-accessdate">. Retrieved <span class="nowrap">April 21,</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=z%2FVM+%3E+z%2FVM+6.2.0+%3E+Application+Programming+%3E+z%2FVM+V6R2+OpenExtensions+POSIX+Conformance+Document+%3E+POSIX.1+Conformance+Document+%3E+Section+3.+Process+Primitives+%3E+3.1+Process+Creation+and+Execution+%3E+3.1.1+Process+Creation&rft.pub=IBM&rft_id=http%3A%2F%2Fwww-01.ibm.com%2Fsupport%2Fknowledgecenter%2FSSB27U_6.2.0%2Fcom.ibm.zvm.v620.dmsp0%2Fhcsp0c0022.htm%2523wq47%3Flang%3Den&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFork+%28system+call%29" class="Z3988"></span></span> </li> </ol></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Fork_(system_call)&oldid=1256826465">https://en.wikipedia.org/w/index.php?title=Fork_(system_call)&oldid=1256826465</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Process_(computing)" title="Category:Process (computing)">Process (computing)</a></li><li><a href="/wiki/Category:C_POSIX_library" title="Category:C POSIX library">C POSIX library</a></li><li><a href="/wiki/Category:System_calls" title="Category:System calls">System calls</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li><li><a href="/wiki/Category:All_articles_with_unsourced_statements" title="Category:All articles with unsourced statements">All articles with unsourced statements</a></li><li><a href="/wiki/Category:Articles_with_unsourced_statements_from_May_2015" title="Category:Articles with unsourced statements from May 2015">Articles with unsourced statements from May 2015</a></li><li><a href="/wiki/Category:All_articles_with_failed_verification" title="Category:All articles with failed verification">All articles with failed verification</a></li><li><a href="/wiki/Category:Articles_with_failed_verification_from_November_2019" title="Category:Articles with failed verification from November 2019">Articles with failed verification from November 2019</a></li><li><a href="/wiki/Category:Articles_needing_additional_references_from_February_2015" title="Category:Articles needing additional references from February 2015">Articles needing additional references from February 2015</a></li><li><a href="/wiki/Category:All_articles_needing_additional_references" title="Category:All articles needing additional references">All articles needing additional references</a></li><li><a href="/wiki/Category:Articles_with_unsourced_statements_from_October_2013" title="Category:Articles with unsourced statements from October 2013">Articles with unsourced statements from October 2013</a></li><li><a href="/wiki/Category:Articles_with_example_C_code" title="Category:Articles with example C code">Articles with example C code</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 11 November 2024, at 19:29<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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