78 lines
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78 lines
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<!--replace-end-7--><!--replace-end-4--><!--replace-end-1--></head><body><div class="ui fluid container universe"><!--replace-start-2--><!--replace-start-3--><!--replace-start-6--><div class="ui text container" id="zettel-container" style="position: relative"><div class="zettel-view"><article class="ui raised attached segment zettel-content"><div class="pandoc"><h1 id="title-h1">fs module</h1><p>File System is an essential built-in module of Node that contains utility methods for working with files and directories.</p><p>Every method associated with <code>fs</code> has a <em>blocking</em> and <em>asynchronous</em> implementation. The former obviously blocks the <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: The Event Loop"><a href="Event_loop.html">event queue</a></span></span>, the latter does not.</p><p>The synchronous methods are useful to have in some contexts but in general and with real-world applications, you should be using the async implementation so as to accord with the single-threaded event-driven architecture of Node.</p><h2 id="common-i0-methods">Common I/0 methods</h2><h3 id="read-directory">Read directory</h3><p>Return a string array of all files in the current directory.</p><pre><code class="js language-js">fs.readdir("./", function (err, files) {
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if (err) {
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console.error(err);
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} else {
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console.log(files);
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}
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});</code></pre><h3 id="read-from-file">Read from file</h3><pre><code class="js language-js">fs.readFile("./lorem.md", "UTF-8", function (err, fileContents) {
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console.log(fileContents);
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});</code></pre><h3 id="write-to-file">Write to file</h3><pre><code class="js language-js">let md = `A new file`;
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fs.writeFile("testFile.md", md.trim(), function () {
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console.log("File was created");
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});</code></pre><h3 id="appending-to-file">Appending to file</h3><pre><code class="js language-js">fs.appendFile("testFile.md", "new content");</code></pre><h3 id="create-directory">Create directory</h3><pre><code class="js language-js">if (!fs.existsSync("directory_name")) {
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fs.mkdir("directory_name", function (err) {
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if (err) {
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console.err(err);
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}
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});
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} else {
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console.warn("Directory already exists");
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}</code></pre><h3 id="rename-and-remove-files">Rename and remove files</h3><pre><code class="js language-js">fs.rename("./filename.js", "./newname.js", function () {
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console.log("file renamed");
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});</code></pre><pre><code class="js language-js">// Remove file
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fs.unlink("./file-to-delete", function (err) {
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if (err) {
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console.error(err);
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}
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});</code></pre><h3 id="rename-and-remove-directories">Rename and remove directories</h3><pre><code class="js language-js">// Best to use synchronous method here
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fs.rmSync("/dir", { recursive: true, force: true });</code></pre><h2 id="streams">Streams</h2><p>See <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: Handling streams with fs"><a href="Streams_in_NodeJS.html">Handling streams with fs</a></span></span></p></div></article><nav class="ui attached segment deemphasized backlinksPane" id="neuron-backlinks-pane"><h3 class="ui header">Backlinks</h3><ul class="backlinks"><li><span class="zettel-link-container cf"><span class="zettel-link"><a href="Streams_in_NodeJS.html">Handling streams with fs</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>When reading from a file, the <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: fs module"><a href="fs.html"><code>fs.readFile()</code></a></span></span> method waits until the entire file has been read before executing the callback. It’s obvious why this might not be ideal in certain cases. If the file is very large you are utilising a lot of <span class="zettel-link-container errors"><span class="zettel-link" title="Wiki-link does not refer to any existing zettel"><a>Memory</a></span></span> for a single process. Additionally, the data you need might appear early in the file, in which case, once you find the data you want, there is no need to read to the end of the file.</p></div></li></ul></li></ul></nav><nav class="ui attached segment deemphasized bottomPane" id="neuron-tags-pane"><div><span class="ui basic label zettel-tag" title="Tag">node-js</span></div></nav><nav class="ui bottom attached icon compact inverted menu blue" id="neuron-nav-bar"><!--replace-start-9--><!--replace-end-9--><a class="right item" href="impulse.html" title="Open Impulse"><i class="wave square icon"></i></a></nav></div></div><!--replace-end-6--><!--replace-end-3--><!--replace-end-2--><div class="ui center aligned container footer-version"><div class="ui tiny image"><a href="https://neuron.zettel.page"><img alt="logo" src="https://raw.githubusercontent.com/srid/neuron/master/assets/neuron.svg" title="Generated by Neuron 1.9.35.3" /></a></div></div></div></body></html>
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