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<!DOCTYPE html> <html lang="en-US"> <head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=Edge"> <title>Safe Saving - SyncFiles Documentation</title> <link rel="shortcut icon" href="/syncfiles/favicon.ico" type="image/x-icon"> <link rel="stylesheet" href="/syncfiles/assets/css/just-the-docs-default.css"> <script type="text/javascript" src="/syncfiles/assets/js/vendor/lunr.min.js"></script> <script type="text/javascript" src="/syncfiles/assets/js/just-the-docs.js"></script> <meta name="viewport" content="width=device-width, initial-scale=1"> <!-- Begin Jekyll SEO tag v2.8.0 --> <title>Safe Saving | SyncFiles Documentation</title> <meta name="generator" content="Jekyll v4.2.2" /> <meta property="og:title" content="Safe Saving" /> <meta property="og:locale" content="en_US" /> <meta name="description" content="Write an awesome description for your new site here. You can edit this line in _config.yml. It will appear in your document head meta (for Google search results) and in your feed.xml site description." /> <meta property="og:description" content="Write an awesome description for your new site here. You can edit this line in _config.yml. It will appear in your document head meta (for Google search results) and in your feed.xml site description." /> <link rel="canonical" href="https://depp.github.io/syncfiles/tech/safe-saving" /> <meta property="og:url" content="https://depp.github.io/syncfiles/tech/safe-saving" /> <meta property="og:site_name" content="SyncFiles Documentation" /> <meta property="og:type" content="website" /> <meta name="twitter:card" content="summary" /> <meta property="twitter:title" content="Safe Saving" /> <script type="application/ld+json"> {"@context":"https://schema.org","@type":"WebPage","description":"Write an awesome description for your new site here. You can edit this line in _config.yml. It will appear in your document head meta (for Google search results) and in your feed.xml site description.","headline":"Safe Saving","url":"https://depp.github.io/syncfiles/tech/safe-saving"}</script> <!-- End Jekyll SEO tag --> </head> <body> <svg xmlns="http://www.w3.org/2000/svg" style="display: none;"> <symbol id="svg-link" viewBox="0 0 24 24"> <title>Link</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-link"> <path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"></path><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"></path> </svg> </symbol> <symbol id="svg-search" viewBox="0 0 24 24"> <title>Search</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-search"> <circle cx="11" cy="11" r="8"></circle><line x1="21" y1="21" x2="16.65" y2="16.65"></line> </svg> </symbol> <symbol id="svg-menu" viewBox="0 0 24 24"> <title>Menu</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-menu"> <line x1="3" y1="12" x2="21" y2="12"></line><line x1="3" y1="6" x2="21" y2="6"></line><line x1="3" y1="18" x2="21" y2="18"></line> </svg> </symbol> <symbol id="svg-arrow-right" viewBox="0 0 24 24"> <title>Expand</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-chevron-right"> <polyline points="9 18 15 12 9 6"></polyline> </svg> </symbol> <symbol id="svg-doc" viewBox="0 0 24 24"> <title>Document</title> <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-file"> <path d="M13 2H6a2 2 0 0
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<span class="k">const</span> <span class="n">FSSpec</span> <span class="o">*</span> <span class="n">source</span><span class="p">,</span>
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<span class="k">const</span> <span class="n">FSSpec</span> <span class="o">*</span> <span class="n">dest</span><span class="p">);</span>
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</code></pre></div></div> <p>This function exchanges the <em>contents</em> of the two files (both forks), and exchanges the modification dates, but leaves the other metadata alone.</p> <p>The recipe for safe saving on HFS volumes is:</p> <ol> <li> <p>Save the document to a temporary file on the same volume.</p> </li> <li> <p>Exchange the contents of the original file and the temporary file with <code class="language-plaintext highlighter-rouge">FSpExchangeFiles</code>.</p> </li> </ol> <p>You can test that <code class="language-plaintext highlighter-rouge">FSpExchangeFiles</code> is supported by a volume by getting the volume parameters. Not all filesystems support this operation.</p> <h2 id="mac-os-x"> <a href="#mac-os-x" class="anchor-heading" aria-labelledby="mac-os-x"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Mac OS X </h2> <p>Mac OS X provides a Unix system call that provides the same functionality as <code class="language-plaintext highlighter-rouge">FSpExchangeFiles</code>, but with a Unix API.</p> <div class="language-c highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">int</span> <span class="nf">exchangedata</span><span class="p">(</span>
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<span class="k">const</span> <span class="kt">char</span> <span class="o">*</span> <span class="n">path1</span>
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<span class="k">const</span> <span class="kt">char</span> <span class="o">*</span> <span class="n">path2</span><span class="p">,</span>
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<span class="kt">unsigned</span> <span class="kt">int</span> <span class="n">options</span><span class="p">);</span>
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</code></pre></div></div> <p>However, this function does not work on APFS.</p> <h2 id="mac-os-x-106"> <a href="#mac-os-x-106" class="anchor-heading" aria-labelledby="mac-os-x-106"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Mac OS X 10.6+ </h2> <p>Starting on Mac OS X 10.6, the Foundation framework provides a method for safely replacing an item on the filesystem with a new item. This method is present on <code class="language-plaintext highlighter-rouge">NSFileManager</code>:</p> <div class="language-objc highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">-</span> <span class="p">(</span><span class="n">BOOL</span><span class="p">)</span><span class="nf">replaceItemAtURL</span><span class="p">:(</span><span class="n">NSURL</span> <span class="o">*</span><span class="p">)</span><span class="nv">originalItemURL</span>
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<span class="nf">withItemAtURL</span><span class="p">:(</span><span class="n">NSURL</span> <span class="o">*</span><span class="p">)</span><span class="nv">newItemURL</span>
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<span class="nf">backupItemName</span><span class="p">:(</span><span class="n">NSString</span> <span class="o">*</span><span class="p">)</span><span class="nv">backupItemName</span>
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<span class="nf">options</span><span class="p">:(</span><span class="n">NSFileManagerItemReplacementOptions</span><span class="p">)</span><span class="nv">options</span>
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<span class="nf">resultingItemURL</span><span class="p">:(</span><span class="n">NSURL</span> <span class="o">*</span> <span class="n">_Nullable</span> <span class="o">*</span><span class="p">)</span><span class="nv">resultingURL</span>
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<span class="nf">error</span><span class="p">:(</span><span class="n">NSError</span> <span class="o">*</span> <span class="n">_Nullable</span> <span class="o">*</span><span class="p">)</span><span class="nv">error</span><span class="p">;</span>
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</code></pre></div></div> <p>This method should be preferred for Mac OS X 10.6 and newer. Unlike <code class="language-plaintext highlighter-rouge">exchangedata()</code>, this function works on APFS.</p> </div> </div> <div class="search-overlay"></div> </div> </body> </html>
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