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docSidebarContainer_YfHR"><div class="sidebarViewport_aRkj"><div class="sidebar_njMd"><nav aria-label="Docs sidebar" class="menu thin-scrollbar menu_SIkG"><ul class="theme-doc-sidebar-menu menu__list"><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="../../index.html">Introduction</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-0/intro.html">Contents and Figures</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-1/b-b-scope-purpose-and-history.html">1. Introduction</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-2/c-b-character-syntax.html">2. Syntax</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-3/d-b-evaluation.html">3. Evaluation and Compilation</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-4/e-b-introduction.html">4. Types and Classes</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-5/f-b-generalized-reference.html">5. Data and Control Flow</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-6/g-b-the-loop-facility.html">6. Iteration</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-7/h-b-object-creation-and-initialization.html">7. Objects</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../category/81-structures-dictionary.html">8. Structures</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-9/j-b-condition-system-concepts.html">9. Conditions</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-10/ba-b-symbol-concepts.html">10. Symbols</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-11/bb-b-package-concepts.html">11. Packages</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-12/bc-b-number-concepts.html">12. Numbers</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-13/bd-b-character-concepts.html">13. Characters</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-14/be-b-cons-concepts.html">14. Conses</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-15/bf-b-array-concepts.html">15. Arrays</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-16/bg-b-string-concepts.html">16. Strings</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-17/bh-b-sequence-concepts.html">17. Sequences</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-18/bi-b-hash-table-concepts.html">18. Hash Tables</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-19/bj-b-overview-of-filenames.html">19. Filenames</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-20/ca-b-file-system-concepts.html">20. Files</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret menu__link--active" aria-expanded="true" href="../cb-b-stream-concepts.html">21. 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href="broadcast-stream-streams_function.html">broadcast-stream-streams</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="broadcast-stream_system-class.html">broadcast-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="clear-input_function.html">clear-input</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="close_function.html">close</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="concatenated-stream_system-class.html">concatenated-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" 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href="make-broadcast-stream_function.html">make-broadcast-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="make-concatenated-stream_function.html">make-concatenated-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="make-echo-stream_function.html">make-echo-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="make-string-input-stream_function.html">make-string-input-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="make-string-output-stream_function.html">make-string-output-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="make-synonym-stream_function.html">make-synonym-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="make-two-way-stream_function.html">make-two-way-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="open-stream-p_function.html">open-stream-p</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link menu__link--active" aria-current="page" tabindex="0" href="open_function.html">open</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="peek-char_function.html">peek-char</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="read-byte_function.html">read-byte</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="read-char-no-hang_function.html">read-char-no-hang</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="read-char_function.html">read-char</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="read-line_function.html">read-line</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="read-sequence_function.html">read-sequence</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="stream-element-type_function.html">stream-element-type</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="stream-error-stream_function.html">stream-error-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="stream-external-format_function.html">stream-external-format</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="stream_system-class.html">stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="streamp_function.html">streamp</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="string-stream_system-class.html">string-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="synonym-stream-symbol_function.html">synonym-stream-symbol</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="synonym-stream_system-class.html">synonym-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="terminal-io_variable.html">terminal-io</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="terpri_fresh-line_function.html">terpri, fresh-line</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="two-way-stream_system-class.html">two-way-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="unread-char_function.html">unread-char</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="with-input-from-string_macro.html">with-input-from-string</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="with-open-file_macro.html">with-open-file</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="with-open-stream_macro.html">with-open-stream</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="with-output-to-string_macro.html">with-output-to-string</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="write-byte_function.html">write-byte</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="write-char_function.html">write-char</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="write-sequence_function.html">write-sequence</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="write-string_write-line_function.html">write-string, write-line</a></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-3 menu__list-item"><a class="menu__link" tabindex="0" href="y-or-n-p_yes-or-no-p_function.html">y-or-n-p, yes-or-no-p</a></li></ul></li></ul></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-22/cc-b-the-lisp-printer.html">22. Printer</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-23/cd-b-reader-concepts.html">23. Reader</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-24/ce-b-system-construction-concepts.html">24. System Construction</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-25/cf-b-the-external-environment.html">25. External Environment</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../environments.html">26. Environments</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../meta-object-protocol.html">27. Meta Object Protocol</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../data-structures.html">28. Data Structures</a></div></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../portability/trivial-packages.html">29. Portability</a></div></li><li class="theme-doc-sidebar-item-link theme-doc-sidebar-item-link-level-1 menu__list-item"><a class="menu__link" href="../../dictionary-entries.html">dictionary-entries</a></li><li class="theme-doc-sidebar-item-category theme-doc-sidebar-item-category-level-1 menu__list-item menu__list-item--collapsed"><div class="menu__list-item-collapsible"><a class="menu__link menu__link--sublist menu__link--sublist-caret" aria-expanded="false" href="../../chap-26/intro.html">Glossary</a></div></li></ul></nav></div></div></aside><main class="docMainContainer_TBSr"><div class="container padding-top--md padding-bottom--lg"><div class="row"><div class="col docItemCol_VOVn"><div class="docItemContainer_Djhp"><article><nav class="theme-doc-breadcrumbs breadcrumbsContainer_Z_bl" aria-label="Breadcrumbs"><ul class="breadcrumbs" itemscope="" itemtype="https://schema.org/BreadcrumbList"><li class="breadcrumbs__item"><a aria-label="Home page" class="breadcrumbs__link" href="../../index.html"><svg viewBox="0 0 24 24" class="breadcrumbHomeIcon_YNFT"><path d="M10 19v-5h4v5c0 .55.45 1 1 1h3c.55 0 1-.45 1-1v-7h1.7c.46 0 .68-.57.33-.87L12.67 3.6c-.38-.34-.96-.34-1.34 0l-8.36 7.53c-.34.3-.13.87.33.87H5v7c0 .55.45 1 1 1h3c.55 0 1-.45 1-1z" fill="currentColor"></path></svg></a></li><li class="breadcrumbs__item"><span class="breadcrumbs__link">21. Streams</span><meta itemprop="position" content="1"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item"><a class="breadcrumbs__link" itemprop="item" href="../../category/212-streams-dictionary.html"><span itemprop="name">21.2 Streams Dictionary</span></a><meta itemprop="position" content="2"></li><li itemscope="" itemprop="itemListElement" itemtype="https://schema.org/ListItem" class="breadcrumbs__item breadcrumbs__item--active"><span class="breadcrumbs__link" itemprop="name">open</span><meta itemprop="position" content="3"></li></ul></nav><div class="tocCollapsible_ETCw theme-doc-toc-mobile tocMobile_ITEo"><button type="button" class="clean-btn tocCollapsibleButton_TO0P">On this page</button></div><div class="theme-doc-markdown markdown"><h1>open</h1>
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||
<!-- -->
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<!-- -->
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<p><strong>open</strong> <span><i>Function</i></span></p>
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<p><strong>Syntax:</strong></p>
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<p><span><b>open</b></span> <em>filespec</em> &key <em>direction element-type</em></p>
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<p><em>if-exists if-does-not-exist external-format</em></p>
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<p>→ stream</p>
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<p><strong>Arguments and Values:</strong></p>
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||
<p><em>filespec</em>—a <span><i>pathname designator</i></span> .</p>
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||
<p><em>direction</em>—one of <!-- -->:input<!-- -->, <!-- -->:output<!-- -->, <!-- -->:io<!-- -->, or <!-- -->:probe<!-- -->. The default is <!-- -->:input<!-- -->.</p>
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||
<p><em>element-type</em>—a <span><i>type specifier</i></span> for <span><i>recognizable subtype</i></span> of <span><b>character</b></span>; or a <span><i>type specifier</i></span> for a <em>finite recognizable subtype</em> of <em>integer</em> ; or one of the <span><i>symbols</i></span> <span><b>signed-byte</b></span>, <span><b>unsigned-byte</b></span>, or <!-- -->:default<!-- -->. The default is <span><b>character</b></span>.</p>
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||
<p><em>if-exists</em>—one of <!-- -->:error<!-- -->, <!-- -->:new-version<!-- -->, <!-- -->:rename<!-- -->, <!-- -->:rename-and-delete<!-- -->, <!-- -->:overwrite<!-- -->, <!-- -->:append<!-- -->, <!-- -->:supersede<!-- -->, or <span><b>nil</b></span>. The default is <!-- -->:new-version<!-- --> if the version component of <em>filespec</em> is <!-- -->:newest<!-- -->, or <!-- -->:error<!-- --> otherwise.</p>
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<p><em>if-does-not-exist</em>—one of <!-- -->:error<!-- -->, <!-- -->:create<!-- -->, or <span><b>nil</b></span>. The default is <!-- -->:error<!-- --> if <em>direction</em> is <!-- -->:input<!-- --> or <em>if-exists</em> is <!-- -->:overwrite<!-- --> or <!-- -->:append<!-- -->; <!-- -->:create<!-- --> if <em>direction</em> is <!-- -->:output<!-- --> or <!-- -->:io<!-- -->, and <em>if-exists</em> is neither <!-- -->:overwrite<!-- --> nor <!-- -->:append<!-- -->; or <span><b>nil</b></span> when <em>direction</em> is <!-- -->:probe<!-- -->.</p>
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<p><em>external-format</em>—an <span><i>external file format designator</i></span> . The default is <!-- -->:default<!-- -->.</p>
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<p><span><i>stream</i></span>—a <span><i>file stream</i></span> or <span><b>nil</b></span>.</p>
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||
<p><strong>Description:</strong></p>
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||
<p><span><b>open</b></span> creates, opens, and returns a <span><i>file stream</i></span> that is connected to the file specified by <em>filespec</em>. <em>Filespec</em> is the name of the file to be opened. If the <em>filespec designator</em> is a <span><i>stream</i></span>, that <span><i>stream</i></span> is not closed first or otherwise affected.</p>
|
||
<p>The keyword arguments to <span><b>open</b></span> specify the characteristics of the <span><i>file stream</i></span> that is returned, and how to handle errors.</p>
|
||
<p>If <em>direction</em> is <!-- -->:input<!-- --> or <!-- -->:probe<!-- -->, or if <em>if-exists</em> is not <!-- -->:new-version<!-- --> and the version component of the <em>filespec</em> is <!-- -->:newest<!-- -->, then the file opened is that file already existing in the file system that has a version greater than that of any other file in the file system whose other pathname components are the same as those of <em>filespec</em>.</p>
|
||
<p>An implementation is required to recognize all of the <span><b>open</b></span> keyword options and to do something reasonable in the context of the host operating system. For example, if a file system does not support distinct file versions and does not distinguish the notions of deletion and expunging, <!-- -->:new-version<!-- --> might be treated the same as <!-- -->:rename<!-- --> or <!-- -->:supersede<!-- -->, and <!-- -->:rename-and-delete<!-- --> might be treated the same as <!-- -->:supersede<!-- -->.</p>
|
||
<span><b>open</b></span>
|
||
<p>:direction</p>
|
||
<p>These are the possible values for <em>direction</em>, and how they affect the nature of the <span><i>stream</i></span> that is created:</p>
|
||
<p>:input</p>
|
||
<p>Causes the creation of an <em>input file stream</em>.</p>
|
||
<p>:output</p>
|
||
<p>Causes the creation of an <em>output file stream</em>.</p>
|
||
<p>:io</p>
|
||
<p>Causes the creation of a <em>bidirectional file stream</em>.</p>
|
||
<p>:probe</p>
|
||
<p>Causes the creation of a “no-directional” <span><i>file stream</i></span>; in effect, the <span><i>file stream</i></span> is</p>
|
||
<p>created and then closed prior to being returned by <span><b>open</b></span>.</p>
|
||
<p>:element-type</p>
|
||
<p>The <em>element-type</em> specifies the unit of transaction for the <span><i>file stream</i></span>. If it is <!-- -->:default<!-- -->, the unit is determined by <span><i>file system</i></span>, possibly based on the <span><i>file</i></span>.</p>
|
||
<p>:if-exists</p>
|
||
<p><em>if-exists</em> specifies the action to be taken if <em>direction</em> is <!-- -->:output<!-- --> or <!-- -->:io<!-- --> and a file of the name <em>filespec</em> already exists. If <em>direction</em> is <!-- -->:input<!-- -->, not supplied, or <!-- -->:probe<!-- -->, <em>if-exists</em> is ignored. These are the results of <span><b>open</b></span> as modified by <em>if-exists</em>:</p>
|
||
<p>:error</p>
|
||
<p>An error of <span><i>type</i></span> <span><b>file-error</b></span> is signaled.</p>
|
||
<p>:new-version</p>
|
||
<p>A new file is created with a larger version number.</p>
|
||
<p>:rename</p>
|
||
<p>The existing file is renamed to some other name and then a new file is created.</p>
|
||
<p>:rename-and-delete</p>
|
||
<p>The existing file is renamed to some other name, then it is deleted but not</p>
|
||
<p>expunged, and then a new file is created.</p>
|
||
<span><b>open</b></span>
|
||
<p>:overwrite</p>
|
||
<p>Output operations on the <span><i>stream</i></span> destructively modify the existing file. If <em>direction</em></p>
|
||
<p>is <!-- -->:io<!-- --> the file is opened in a bidirectional mode that allows both reading and</p>
|
||
<p>writing. The file pointer is initially positioned at the beginning of the file; however,</p>
|
||
<p>the file is not truncated back to length zero when it is opened.</p>
|
||
<p>:append</p>
|
||
<p>Output operations on the <span><i>stream</i></span> destructively modify the existing file. The file</p>
|
||
<p>pointer is initially positioned at the end of the file.</p>
|
||
<p>If <em>direction</em> is <!-- -->:io<!-- -->, the file is opened in a bidirectional mode that allows both</p>
|
||
<p>reading and writing.</p>
|
||
<p>:supersede</p>
|
||
<p>The existing file is superseded; that is, a new file with the same name as the old</p>
|
||
<p>one is created. If possible, the implementation should not destroy the old file until</p>
|
||
<p>the new <span><i>stream</i></span> is closed.</p>
|
||
<span><b>nil</b></span>
|
||
<p>No file or <span><i>stream</i></span> is created; instead, <span><b>nil</b></span> is returned to indicate failure.</p>
|
||
<p>:if-does-not-exist</p>
|
||
<p><em>if-does-not-exist</em> specifies the action to be taken if a file of name <em>filespec</em> does not already exist. These are the results of <span><b>open</b></span> as modified by <em>if-does-not-exist</em>:</p>
|
||
<p>:error</p>
|
||
<p>An error of <span><i>type</i></span> <span><b>file-error</b></span> is signaled.</p>
|
||
<p>:create</p>
|
||
<p>An empty file is created. Processing continues as if the file had already existed but</p>
|
||
<p>no processing as directed by <em>if-exists</em> is performed.</p>
|
||
<span><b>nil</b></span>
|
||
<p>No file or <span><i>stream</i></span> is created; instead, <span><b>nil</b></span> is returned to indicate failure.</p>
|
||
<p>:external-format</p>
|
||
<p>This option selects an <span><i>external file format</i></span> for the <span><i>file</i></span>: The only <span><i>standardized</i></span> value for this option is <!-- -->:default<!-- -->, although <span><i>implementations</i></span> are permitted to define additional <span><i>external file formats</i></span> and <span><i>implementation-dependent</i></span> values returned by <span><b>stream-external-format</b></span> can also be used by <span><i>conforming programs</i></span>.</p>
|
||
<span><b>open</b></span>
|
||
<p>The <em>external-format</em> is meaningful for any kind of <span><i>file stream</i></span> whose <span><i>element type</i></span> is a <span><i>subtype</i></span> of <span><i>character</i></span> . This option is ignored for <span><i>streams</i></span> for which it is not meaningful; however, <span><i>implementations</i></span> may define other <span><i>element types</i></span> for which it is meaningful. The consequences are unspecified if a <span><i>character</i></span> is written that cannot be represented by the given <span><i>external file format</i></span>.</p>
|
||
<p>When a file is opened, a <span><i>file stream</i></span> is constructed to serve as the file system’s ambassador to the Lisp environment; operations on the <span><i>file stream</i></span> are reflected by operations on the file in the file system.</p>
|
||
<p>A file can be deleted, renamed, or destructively modified by <span><b>open</b></span>.</p>
|
||
<p>For information about opening relative pathnames, see Section 19.2.3 (Merging Pathnames).</p>
|
||
<p><strong>Examples:</strong></p>
|
||
<div class="language-lisp codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-lisp codeBlock_bY9V thin-scrollbar" style="color:#393A34;background-color:#f6f8fa"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token punctuation" style="color:#393A34">(</span><span class="token car">open</span><span class="token plain"> *filespec* </span><span class="token lisp-property property" style="color:#36acaa">:direction</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:probe</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #<Closed Probe File Stream...> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">setq</span><span class="token plain"> q </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">merge-pathnames</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">user-homedir-pathname</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"test"</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">→ #<PATHNAME </span><span class="token lisp-property property" style="color:#36acaa">:HOST</span><span class="token plain"> NIL </span><span class="token lisp-property property" style="color:#36acaa">:DEVICE</span><span class="token plain"> *device-name* </span><span class="token lisp-property property" style="color:#36acaa">:DIRECTORY</span><span class="token plain"> *directory-name* </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token lisp-property property" style="color:#36acaa">:NAME</span><span class="token plain"> </span><span class="token string" style="color:#e3116c">"test"</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:TYPE</span><span class="token plain"> NIL </span><span class="token lisp-property property" style="color:#36acaa">:VERSION</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:NEWEST></span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">open</span><span class="token plain"> *filespec* </span><span class="token lisp-property property" style="color:#36acaa">:if-does-not-exist</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:create</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #<Input File Stream...> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token keyword" style="color:#00009f">setq</span><span class="token plain"> s </span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">open</span><span class="token plain"> *filespec* </span><span class="token lisp-property property" style="color:#36acaa">:direction</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:probe</span><span class="token punctuation" style="color:#393A34">)</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #<Closed Probe File Stream...> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">truename</span><span class="token plain"> s</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → #<PATHNAME </span><span class="token lisp-property property" style="color:#36acaa">:HOST</span><span class="token plain"> NIL </span><span class="token lisp-property property" style="color:#36acaa">:DEVICE</span><span class="token plain"> *device-name* </span><span class="token lisp-property property" style="color:#36acaa">:DIRECTORY</span><span class="token plain"> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain">*directory-name* </span><span class="token lisp-property property" style="color:#36acaa">:NAME</span><span class="token plain"> *filespec* </span><span class="token lisp-property property" style="color:#36acaa">:TYPE</span><span class="token plain"> *extension* </span><span class="token lisp-property property" style="color:#36acaa">:VERSION</span><span class="token plain"> 1> </span><br></span><span class="token-line" style="color:#393A34"><span class="token plain"></span><span class="token punctuation" style="color:#393A34">(</span><span class="token car">open</span><span class="token plain"> s </span><span class="token lisp-property property" style="color:#36acaa">:direction</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:output</span><span class="token plain"> </span><span class="token lisp-property property" style="color:#36acaa">:if-exists</span><span class="token plain"> </span><span class="token boolean" style="color:#36acaa">nil</span><span class="token punctuation" style="color:#393A34">)</span><span class="token plain"> → NIL </span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 0 24 24" class="copyButtonSuccessIcon_LjdS"><path fill="currentColor" d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div>
|
||
<p><strong>Affected By:</strong></p>
|
||
<p>The nature and state of the host computer’s <span><i>file system</i></span>.</p>
|
||
<p><strong>Exceptional Situations:</strong></p>
|
||
<p>If <em>if-exists</em> is <!-- -->:error<!-- -->, (subject to the constraints on the meaning of <em>if-exists</em> listed above), an error of <span><i>type</i></span> <span><b>file-error</b></span> is signaled.</p>
|
||
<p>If <em>if-does-not-exist</em> is <!-- -->:error<!-- --> (subject to the constraints on the meaning of <em>if-does-not-exist</em> listed above), an error of <span><i>type</i></span> <span><b>file-error</b></span> is signaled.</p>
|
||
<p>If it is impossible for an implementation to handle some option in a manner close to what is specified here, an error of <span><i>type</i></span> <span><b>error</b></span> might be signaled.</p>
|
||
<p>An error of <span><i>type</i></span> <span><b>file-error</b></span> is signaled if (wild-pathname-p <em>filespec</em>) returns true.</p>
|
||
<p>An error of <span><i>type</i></span> <span><b>error</b></span> is signaled if the <em>external-format</em> is not understood by the <span><i>implementation</i></span>.</p>
|
||
<p>The various <span><i>file systems</i></span> in existence today have widely differing capabilities, and some aspects of the <span><i>file system</i></span> are beyond the scope of this specification to define. A given <span><i>implementation</i></span> might not be able to support all of these options in exactly the manner stated. An <span><i>implementation</i></span> is required to recognize all of these option keywords and to try to do something “reasonable” in the context of the host <span><i>file system</i></span>. Where necessary to accomodate the <span><i>file system</i></span>, an <span><i>implementation</i></span></p>
|
||
<p>deviate slightly from the semantics specified here without being disqualified for consideration as a <span><i>conforming implementation</i></span>. If it is utterly impossible for an <span><i>implementation</i></span> to handle some option in a manner similar to what is specified here, it may simply signal an error.</p>
|
||
<p>With regard to the <!-- -->:element-type<!-- --> option, if a <span><i>type</i></span> is requested that is not supported by the <span><i>file system</i></span>, a substitution of types such as that which goes on in <em>upgrading</em> is permissible. As a minimum requirement, it should be the case that opening an <em>output stream</em> to a <span><i>file</i></span> in a given <span><i>element type</i></span> and later opening an <em>input stream</em> to the same <span><i>file</i></span> in the same <span><i>element type</i></span> should work compatibly.</p>
|
||
<p><strong>See Also:</strong></p>
|
||
<p><span><b>with-open-file</b></span>, <span><b>close</b></span>, <span><b>pathname</b></span>, <span><b>logical-pathname</b></span>, Section 19.2.3 (Merging Pathnames), Section 19.1.2 (Pathnames as Filenames)</p>
|
||
<p><strong>Notes:</strong></p>
|
||
<p><span><b>open</b></span> does not automatically close the file when an abnormal exit occurs.</p>
|
||
<p>When <em>element-type</em> is a <span><i>subtype</i></span> of <span><b>character</b></span>, <span><b>read-char</b></span> and/or <span><b>write-char</b></span> can be used on the resulting <span><i>file stream</i></span>.</p>
|
||
<p>When <em>element-type</em> is a <span><i>subtype</i></span> of <em>integer</em> , <span><b>read-byte</b></span> and/or <span><b>write-byte</b></span> can be used on the resulting <span><i>file stream</i></span>.</p>
|
||
<p>When <em>element-type</em> is <!-- -->:default<!-- -->, the <span><i>type</i></span> can be determined by using <span><b>stream-element-type</b></span>.</p>
|
||
<h2 class="anchor anchorWithStickyNavbar_LWe7" id="expanded-reference-open">Expanded Reference: open<a href="open_function.html#expanded-reference-open" class="hash-link" aria-label="Direct link to Expanded Reference: open" title="Direct link to Expanded Reference: open"></a></h2>
|
||
<div class="theme-admonition theme-admonition-tip admonition_xJq3 alert alert--success"><div class="admonitionHeading_Gvgb"><span class="admonitionIcon_Rf37"><svg viewBox="0 0 12 16"><path fill-rule="evenodd" d="M6.5 0C3.48 0 1 2.19 1 5c0 .92.55 2.25 1 3 1.34 2.25 1.78 2.78 2 4v1h5v-1c.22-1.22.66-1.75 2-4 .45-.75 1-2.08 1-3 0-2.81-2.48-5-5.5-5zm3.64 7.48c-.25.44-.47.8-.67 1.11-.86 1.41-1.25 2.06-1.45 3.23-.02.05-.02.11-.02.17H5c0-.06 0-.13-.02-.17-.2-1.17-.59-1.83-1.45-3.23-.2-.31-.42-.67-.67-1.11C2.44 6.78 2 5.65 2 5c0-2.2 2.02-4 4.5-4 1.22 0 2.36.42 3.22 1.19C10.55 2.94 11 3.94 11 5c0 .66-.44 1.78-.86 2.48zM4 14h5c-.23 1.14-1.3 2-2.5 2s-2.27-.86-2.5-2z"></path></svg></span>tip</div><div class="admonitionContent_BuS1"><p>TODO: Please contribute to this page by adding explanations and examples</p></div></div>
|
||
<div class="language-lisp codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#393A34;--prism-background-color:#f6f8fa"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-lisp codeBlock_bY9V thin-scrollbar" style="color:#393A34;background-color:#f6f8fa"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#393A34"><span class="token punctuation" style="color:#393A34">(</span><span class="token car">open</span><span class="token plain"> </span><span class="token punctuation" style="color:#393A34">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg viewBox="0 0 24 24" class="copyButtonIcon_y97N"><path fill="currentColor" d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg viewBox="0 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