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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">The <code>$PATH</code></h1><p>We know that <code>$PATH</code> is an <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: Environmental and shell variables"><a href="Environmental_and_shell_variables.html">environment variable</a></span></span>. This variable keeps track of directories <strong>where executables are found</strong>.</p><p>Whenever any command is run, the shell looks up the directories contained in the <code>PATH</code> for the target executable file and runs it. We can see this is the case by using the <code>which</code> command which traces the executable of bash commands. Take the <code>echo</code> program:</p><pre><code class="bash language-bash">which echo
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# echo: shell built-in command</code></pre><p>Or <code>npm</code> :</p><pre><code class="bash language-bash">which npm
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/home/thomas/.nvm/versions/node/v19.4.0/bin/npm</code></pre><p>By default the path will always contain the following locations:</p><ul><li><code>/usr/bin</code></li><li><code>/usr/sbin</code></li><li><code>/usr/local/bin</code></li><li><code>/usr/local/sbin</code></li><li><code>/bin</code></li><li><code>/sbin</code></li></ul><p>All the inbuilt terminal programs reside at these locations and most of them are at <code>/usr/bin</code>. This is why they run automatically without error. If you attempt to run a program that doesn’t reside at these locations then you will get an error along the lines of <code>program x is not found in PATH</code>.</p><h2 id="structure-of-the-path">Structure of the PATH</h2><pre><code class="bash language-bash">/home/thomas/.nvm/versions/node/v19.4.0/bin:
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/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/lib/jvm/default/bin:
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/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl</code></pre><h2 id="adding-to-the-path">Adding to the PATH</h2><p>Only the default directories load to the PATH on every session. How then can we add custom directories to the path without them being lost every time we start a new session? Remember that the user config <code>.bashrc</code> loads on init for every bash session. Therefore, if we set the custom path in this file, it will be created every time we start a session. This is why when you add a new program it often ask you to append a script to the bottom of your <code>.bashrc</code> .</p><p>For example, at the bottom of my <code>.zshrc</code> on my work computer I have:</p><pre><code class="bash language-bash">export CHROME_BIN=/mnt/c/Program\\ Files\\ \\(x86\\)/Google/Chrome/Application/chrome.exe</code></pre><p>This enables me to access the Chromium binaries from my terminal session (needed for running Angular tests) but it doesn’t add it to the path, it creates an environment variable on every session.</p><p>For demonstration, let’s add a user’s desktop directory to the PATH.</p><p>First we go to the <code>.bashrc</code> and add the <code>export</code> command. Remember that this is the command for creating a new environment variable:</p><pre><code class="bash language-bash">export PATH="$PATH=:~/Desktop"</code></pre><p>We force a reload of the <code>.bashrc</code> with the command:</p><pre><code class="bash language-bash">source ~/.bashrc</code></pre><p>Then we can check this directory has been added to the path with an echo</p><pre><code class="bash language-bash">echo $PATH
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...:~/Desktop</code></pre></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="Passing_arguments_and_options_to_Bash_scripts.html">Passing arguments and options to Bash scripts</a></span></span><ul class="context-list" style="zoom: 85%;"><li class="item"><div class="pandoc"><p>When we run a program like <code>cd</code> or <code>npm</code> we don’t have to type <code>./cd.sh</code> or <code>./npm.sh</code>. This is because a reference to the program file is already in our <span class="zettel-link-container cf"><span class="zettel-link" title="Zettel: The $PATH"><a href="The_PATH.html"><code>$PATH</code></a></span></span>.</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">shell</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> |