mirror of
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temp
This commit is contained in:
Amy de Buitléir
parent
a23029eb15
commit
00bfdf2c0f
12 changed files with 161 additions and 140 deletions
161
index.html
161
index.html
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@ -840,7 +840,8 @@ a path</code></pre>
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</div>
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<div class="paragraph">
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<p>If an expression can be interpreted as a path, Nix will do so.
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This is useful, because paths are <em>far</em> more commonly used in Nix expressions that arithmetic operators.
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This is useful, because paths are <em>far</em> more commonly used in Nix expressions
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than arithmetic operators.
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In this case, Nix interpreted <code>6/2</code> as a relative path from the current directory,
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which in the above example was <code>/home/amy/codeberg/nix-book</code>.</p>
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</div>
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@ -1617,9 +1618,9 @@ This is an important topic, so we will cover it separately in <a href="#argument
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<p>To specify an attribute set as a function parameter, we use a <em>set pattern</em>,
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which has the form</p>
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</div>
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<div class="literalblock">
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<div class="listingblock">
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<div class="content">
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<pre class="nowrap">{ _name1_, _name2_, ... }</pre>
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<pre class="pygments highlight nowrap"><code>{ <em>name1</em>, <em>name2</em>, ... }</code></pre>
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</div>
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</div>
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<div class="paragraph">
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@ -1858,9 +1859,10 @@ using the attribute selection operator (<code>.</code>).</p>
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<div class="sectionbody">
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<div class="paragraph">
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<p>Before learning to write Nix flakes, let’s learn how to use them. I’ve
|
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created a simple example of a flake in this git
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<a href="https://codeberg.org/mhwombat/hello-flake">repository</a>. To run this
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flake, you don’t need to install anything; simply run the command below.
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created a simple example of a flake in this git repository:
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<a href="https://codeberg.org/mhwombat/hello-flake" class="bare">https://codeberg.org/mhwombat/hello-flake</a>.
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To run this flake, you don’t need to install anything;
|
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simply run the command below.
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The first time you use a flake, Nix has to fetch and build it, which
|
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may take time. Subsequent invocations should be instantaneous.</p>
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</div>
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@ -1909,8 +1911,8 @@ directly available.</p>
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<div class="literalblock">
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<div class="content">
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<pre class="nowrap">$ exit
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$ hello-flake
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sh: line 3: hello-flake: command not found</pre>
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$ hello-flake # Won't work outside development shell
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bash: line 24: hello-flake: command not found</pre>
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</div>
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</div>
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<div class="paragraph">
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@ -2028,13 +2030,7 @@ is always called <code>flake.nix</code>.</p>
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<span class="normal">38</span>
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<span class="normal">39</span>
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<span class="normal">40</span>
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<span class="normal">41</span>
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<span class="normal">42</span>
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<span class="normal">43</span>
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<span class="normal">44</span></pre></div></td><td class="code"><div><pre><span></span><span class="tok-p">{</span>
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<span class="tok-c1"># See https://github.com/mhwombat/nix-for-numbskulls/blob/main/flakes.md</span>
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<span class="tok-c1"># for a brief overview of what each section in a flake should or can contain.</span>
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<span class="normal">41</span></pre></div></td><td class="code"><div><pre><span></span><span class="tok-p">{</span>
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<span class="tok-ss">description</span> <span class="tok-o">=</span> <span class="tok-s2">"a very simple and friendly flake"</span><span class="tok-p">;</span>
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<span class="tok-ss">inputs</span> <span class="tok-o">=</span> <span class="tok-p">{</span>
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@ -2081,7 +2077,7 @@ is always called <code>flake.nix</code>.</p>
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<div class="paragraph">
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<p>If this is your first time seeing a flake definition, it probably looks
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intimidating.
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Flakes are written in the Nix language, introduced in an earlier chapter.
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Flakes are written in the Nix language, introduced in <a href="#_the_nix_language_">[_the_nix_language_]</a>.
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However, you don’t really need to know Nix to follow this example.
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For now, I’d like to focus on the inputs section.</p>
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</div>
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@ -2154,11 +2150,11 @@ flakes. The important thing to note is that the <code>hello-flake</code> package
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"systems": "systems"
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},
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"locked": {
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"lastModified": 1681202837,
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"narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
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"lastModified": 1731533236,
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"narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
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"owner": "numtide",
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"repo": "flake-utils",
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"rev": "cfacdce06f30d2b68473a46042957675eebb3401",
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"rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
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"type": "github"
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},
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"original": {
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@ -2169,11 +2165,11 @@ flakes. The important thing to note is that the <code>hello-flake</code> package
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},
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"nixpkgs": {
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"locked": {
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"lastModified": 1681665000,
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"narHash": "sha256-hDGTR59wC3qrQZFxVi2U3vTY+r02+Okbq080hO1C4Nk=",
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"lastModified": 1757873102,
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"narHash": "sha256-kYhNxLlYyJcUouNRazBufVfBInMWMyF+44xG/xar2yE=",
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"owner": "NixOS",
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"repo": "nixpkgs",
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"rev": "3a6205d9f79fe526be03d8c465403b118ca4cf37",
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"rev": "88cef159e47c0dc56f151593e044453a39a6e547",
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"type": "github"
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},
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"original": {
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|
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@ -2509,41 +2505,12 @@ standard environment version), <code>developPackage</code>, <code>callCabal2Nix<
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<p>Now that we have a better understanding of the structure of <code>flake.nix</code>,
|
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let’s have a look at the one we saw earlier, in the <code>hello-flake</code> repo.
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If you compare this flake definition to the colour-coded template
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presented in the previous section, most of it should look familiar.</p>
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presented in <a href="#_a_generic_flake">Chapter 6, <em>A generic flake</em></a>, most of it should look familiar.</p>
|
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</div>
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<div class="listingblock">
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<div class="title">flake.nix</div>
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<div class="content">
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<pre class="pygments highlight nowrap"><code data-lang="nix"><div class="lineno"><table class="linenotable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
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||||
<span class="normal"> 2</span>
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||||
<span class="normal"> 3</span>
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||||
<span class="normal"> 4</span>
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||||
<span class="normal"> 5</span>
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<span class="normal"> 6</span>
|
||||
<span class="normal"> 7</span>
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<span class="normal"> 8</span>
|
||||
<span class="normal"> 9</span>
|
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<span class="normal">10</span>
|
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<span class="normal">11</span>
|
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<span class="normal">12</span>
|
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<span class="normal">13</span>
|
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<span class="normal">14</span>
|
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<span class="normal">15</span>
|
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<span class="normal">16</span>
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<span class="normal">17</span>
|
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<span class="normal">18</span>
|
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<span class="normal">19</span>
|
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<span class="normal">20</span>
|
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<span class="normal">21</span>
|
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<span class="normal">22</span>
|
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<span class="normal">23</span>
|
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<span class="normal">24</span>
|
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<span class="normal">25</span>
|
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<span class="normal">26</span>
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<span class="normal">27</span>
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<span class="normal">28</span>
|
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<span class="normal">29</span>
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<span class="normal">30</span></pre></div></td><td class="code"><div><pre><span></span><span class="tok-p">{</span>
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<pre class="pygments highlight nowrap"><code data-lang="nix"><span></span><span class="tok-p">{</span>
|
||||
<span class="tok-ss">description</span> <span class="tok-o">=</span> <span class="tok-s2">"a very simple and friendly flake"</span><span class="tok-p">;</span>
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||||
|
||||
<span class="tok-ss">inputs</span> <span class="tok-o">=</span> <span class="tok-p">{</span>
|
||||
|
|
@ -2572,8 +2539,7 @@ presented in the previous section, most of it should look familiar.</p>
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|||
<span class="tok-p">};</span>
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<span class="tok-p">}</span>
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||||
<span class="tok-p">);</span>
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<span class="tok-p">}</span>
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</pre></div></td></tr></table></div></code></pre>
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||||
<span class="tok-p">}</span></code></pre>
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</div>
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||||
</div>
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<div class="paragraph">
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|
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@ -2758,7 +2724,7 @@ so can’t we just run it?</p>
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|||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ hello-flake
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Hello from your flake!</pre>
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||||
bash: line 16: hello-flake: command not found</pre>
|
||||
</div>
|
||||
</div>
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<div class="paragraph">
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||||
|
|
@ -2860,7 +2826,7 @@ Here’s the modified <code>hello-flake</code> file.</p>
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|||
</div>
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||||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ ./hello-flake
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||||
<pre class="nowrap">$ ./hello-flake # Won't work
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||||
./hello-flake: line 3: cowsay: command not found</pre>
|
||||
</div>
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||||
</div>
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||||
|
|
@ -2991,7 +2957,7 @@ It’s just a warning, though; the script runs correctly.</p>
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|||
<pre class="nowrap">$ nix develop
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||||
warning: Git tree '/home/amy/codeberg/nix-book/source/modify-hello-flake/hello-flake' is dirty
|
||||
$ which cowsay # is it available now?
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||||
/nix/store/gfi27h4y5n4aralcxrc0377p8mjb1cvb-cowsay-3.7.0/bin/cowsay
|
||||
/nix/store/y5kz17amqc5gn1yvga9wj3vsjz8s1f0c-cowsay-3.8.4/bin/cowsay
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||||
$ ./hello-flake
|
||||
________________________
|
||||
< Hello from your flake! >
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||||
|
|
@ -3009,9 +2975,9 @@ $ exit</pre>
|
|||
</div>
|
||||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ nix run
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||||
<pre class="nowrap">$ nix run # Won't work
|
||||
warning: Git tree '/home/amy/codeberg/nix-book/source/modify-hello-flake/hello-flake' is dirty
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||||
/nix/store/7p4migpqjsr86xqj4dxlpvma3h3y2bzi-hello-flake/bin/hello-flake: line 3: cowsay: command not found</pre>
|
||||
/nix/store/rnjqkk7a8sz6wrm1qb1hxssy7qlgaa85-hello-flake/bin/hello-flake: line 3: cowsay: command not found</pre>
|
||||
</div>
|
||||
</div>
|
||||
<div class="paragraph">
|
||||
|
|
@ -3151,7 +3117,7 @@ specifying the full path to cowsay.</p>
|
|||
Haskell, Python, Java, C, C#, or Rust,
|
||||
the language build system will usually do all that is required
|
||||
to make the dependencies visible to the program at runtime.
|
||||
In this case, adding the dependency to <code>buildInputs</code> is sufficient.</p>
|
||||
In that case, adding the dependency to <code>buildInputs</code> is sufficient.</p>
|
||||
</div>
|
||||
</td>
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||||
</tr>
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|
|
@ -3182,7 +3148,7 @@ we’ll see next.</p>
|
|||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ cat result/bin/hello-flake
|
||||
#!/nix/store/zlf0f88vj30sc7567b80l52d19pbdmy2-bash-5.2-p15/bin/sh
|
||||
#!/nix/store/q7sqwn7i6w2b67adw0bmix29pxg85x3w-bash-5.3p3/bin/sh
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||||
|
||||
echo "Hello from your flake!"</pre>
|
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</div>
|
||||
|
|
@ -3195,9 +3161,9 @@ echo "Hello from your flake!"</pre>
|
|||
<pre class="nowrap">$ nix build
|
||||
warning: Git tree '/home/amy/codeberg/nix-book/source/modify-hello-flake/hello-flake' is dirty
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||||
$ cat result/bin/hello-flake
|
||||
#!/nix/store/zlf0f88vj30sc7567b80l52d19pbdmy2-bash-5.2-p15/bin/sh
|
||||
#!/nix/store/q7sqwn7i6w2b67adw0bmix29pxg85x3w-bash-5.3p3/bin/sh
|
||||
|
||||
/nix/store/gfi27h4y5n4aralcxrc0377p8mjb1cvb-cowsay-3.7.0/bin/cowsay "Hello from your flake!"</pre>
|
||||
/nix/store/y5kz17amqc5gn1yvga9wj3vsjz8s1f0c-cowsay-3.8.4/bin/cowsay "Hello from your flake!"</pre>
|
||||
</div>
|
||||
</div>
|
||||
<div class="paragraph">
|
||||
|
|
@ -3207,8 +3173,8 @@ don’t need to <code>git push</code> the changes until we’re ready to
|
|||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ git commit hello-flake flake.nix -m 'added bovine feature'
|
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[main 6523897] added bovine feature
|
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2 files changed, 13 insertions(+), 4 deletions(-)
|
||||
[main a10700e] added bovine feature
|
||||
2 files changed, 13 insertions(+), 1 deletion(-)
|
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$ nix run
|
||||
________________________
|
||||
< Hello from your flake! >
|
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|
|
@ -3416,7 +3382,7 @@ You can come back to this section later to learn more.</p>
|
|||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ nix shell nixpkgs#ghc
|
||||
$ runghc Main.hs
|
||||
$ runghc Main.hs # Won't work
|
||||
|
||||
Main.hs:1:1: error: [GHC-87110]
|
||||
Could not find module ‘Network.HostName’.
|
||||
|
|
@ -3435,7 +3401,7 @@ Let’s exit that shell and try again, this time adding the <code>hostname</
|
|||
<div class="content">
|
||||
<pre class="nowrap">$ exit
|
||||
$ nix shell nixpkgs#ghc nixpkgs#hostname
|
||||
$ runghc Main.hs
|
||||
$ runghc Main.hs # Won't work
|
||||
|
||||
Main.hs:1:1: error: [GHC-87110]
|
||||
Could not find module ‘Network.HostName’.
|
||||
|
|
@ -3458,7 +3424,7 @@ The package we want is in the <em>package set</em> called <code>haskellPackages<
|
|||
<div class="content">
|
||||
<pre class="nowrap">$ exit
|
||||
$ nix shell nixpkgs#ghc nixpkgs#haskellPackages.hostname
|
||||
$ runghc Main.hs
|
||||
$ runghc Main.hs # Won't work
|
||||
|
||||
Main.hs:1:1: error: [GHC-87110]
|
||||
Could not find module ‘Network.HostName’.
|
||||
|
|
@ -3496,11 +3462,6 @@ Your hostname is: wombat11k</pre>
|
|||
<div class="paragraph">
|
||||
<p>Success! Now we know the program works.</p>
|
||||
</div>
|
||||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ exit</pre>
|
||||
</div>
|
||||
</div>
|
||||
</div>
|
||||
</div>
|
||||
<div class="sect3">
|
||||
|
|
@ -3600,7 +3561,7 @@ First we’ll try building the package manually.
|
|||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ cabal build
|
||||
sh: line 46: cabal: command not found</pre>
|
||||
sh: line 42: cabal: command not found</pre>
|
||||
</div>
|
||||
</div>
|
||||
<div class="paragraph">
|
||||
|
|
@ -3808,9 +3769,9 @@ warning: creating lock file '"/home/amy/codeberg/nix-book/source/new-flake/haske
|
|||
• Added input 'flake-parts/nixpkgs-lib':
|
||||
'github:nix-community/nixpkgs.lib/a73b9c743612e4244d865a2fdee11865283c04e6?narHash=sha256-x2rJ%2BOvzq0sCMpgfgGaaqgBSwY%2BLST%2BWbZ6TytnT9Rk%3D' (2025-08-10)
|
||||
• Added input 'haskell-flake':
|
||||
'github:srid/haskell-flake/73e3891fb135c679a1c30fae4b101e5b41b8ca61?narHash=sha256-%2B99fEAk0HwjYgIW2tEOs7ayBDxnU9NAM5E29ZxgyX40%3D' (2025-08-31)
|
||||
'github:srid/haskell-flake/2acbf1c9bb7aac38b59dcc3c1bd78911cf37e42c?narHash=sha256-jwZT6Ns4BXlrFHaXjZgZwfhSaw8nTCTKZ8fCDylrONM%3D' (2025-09-14)
|
||||
• Added input 'nixpkgs':
|
||||
'github:nixos/nixpkgs/c6a788f552b7b7af703b1a29802a7233c0067908?narHash=sha256-6n/n1GZQ/vi%2BLhFXMSyoseKdNfc2QQaSBXJdgamrbkE%3D' (2025-09-03)
|
||||
'github:nixos/nixpkgs/6d7ec06d6868ac6d94c371458fc2391ded9ff13d?narHash=sha256-fEvTiU4s9lWgW7mYEU/1QUPirgkn%2BodUBTaindgiziY%3D' (2025-09-13)
|
||||
warning: Git tree '/home/amy/codeberg/nix-book/source/new-flake/haskell-flake/hello-haskell' is dirty</pre>
|
||||
</div>
|
||||
</div>
|
||||
|
|
@ -3847,7 +3808,7 @@ We need to add this to the repo, and commit all important files.</p>
|
|||
<div class="content">
|
||||
<pre class="nowrap">$ git add flake.lock
|
||||
$ git commit -a -m 'initial commit'
|
||||
[master (root-commit) d1f6c9b] initial commit
|
||||
[master (root-commit) d35f8fd] initial commit
|
||||
5 files changed, 170 insertions(+)
|
||||
create mode 100644 LICENSE
|
||||
create mode 100644 Main.hs
|
||||
|
|
@ -4049,7 +4010,7 @@ First we’ll try building the package manually.
|
|||
</div>
|
||||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ python -m build
|
||||
<pre class="nowrap">$ python -m build # Won't work
|
||||
/nix/store/iyff8129iampdw13nlfqalzhxy8y1hi9-python3-3.13.6/bin/python: No module named build</pre>
|
||||
</div>
|
||||
</div>
|
||||
|
|
@ -4252,7 +4213,7 @@ something like this.</p>
|
|||
</div>
|
||||
<div class="literalblock">
|
||||
<div class="content">
|
||||
<pre class="nowrap">$ nix build
|
||||
<pre class="nowrap">$ nix build # Won't work
|
||||
error: Path 'flake.nix' in the repository "/home/amy/codeberg/nix-book/source/new-flake/python-flake/hello-python" is not tracked by Git.
|
||||
|
||||
To make it visible to Nix, run:
|
||||
|
|
@ -4261,8 +4222,8 @@ error: Path 'flake.nix' in the repository "/home/amy/codeberg/nix-book/source/ne
|
|||
</div>
|
||||
</div>
|
||||
<div class="paragraph">
|
||||
<p>Why can’t it find <code>flake.nix</code>? Nix flakes only “see” files that are
|
||||
part of the repository. We need to add all of the important files to the
|
||||
<p>Nix flakes only “see” files that are part of the repository.
|
||||
We need to add all of the important files to the
|
||||
repo before building or running the flake.</p>
|
||||
</div>
|
||||
<div class="literalblock">
|
||||
|
|
@ -4276,7 +4237,7 @@ warning: creating lock file '"/home/amy/codeberg/nix-book/source/new-flake/pytho
|
|||
• Added input 'flake-utils/systems':
|
||||
'github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e?narHash=sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768%3D' (2023-04-09)
|
||||
• Added input 'nixpkgs':
|
||||
'github:NixOS/nixpkgs/9aaf71a4a74d835ec05ac3ddf5fc1b859e005c41?narHash=sha256-%2B0iaqsEjfaIZMuRNGO%2BwC0uVazT5b%2BW38wB7Uv0kA5Y%3D' (2025-09-06)
|
||||
'github:NixOS/nixpkgs/5ad881b15fb2b63c2f127533ca59f840fcc24c3f?narHash=sha256-P8XdKg87fR5PpCjIgMH%2B05PDwhdmlNrigsvChdHfyaw%3D' (2025-09-14)
|
||||
warning: Git tree '/home/amy/codeberg/nix-book/source/new-flake/python-flake/hello-python' is dirty</pre>
|
||||
</div>
|
||||
</div>
|
||||
|
|
@ -4312,7 +4273,7 @@ We need to add this to the repo, and commit all important files.</p>
|
|||
<div class="content">
|
||||
<pre class="nowrap">$ git add flake.lock
|
||||
$ git commit -a -m 'initial commit'
|
||||
[master (root-commit) 887d465] initial commit
|
||||
[master (root-commit) 2af9bd5] initial commit
|
||||
4 files changed, 127 insertions(+)
|
||||
create mode 100644 flake.lock
|
||||
create mode 100644 flake.nix
|
||||
|
|
@ -4559,7 +4520,7 @@ However, you can use any of the flake reference styles defined in <a href="#flak
|
|||
but you don’t want to bother writing a cabal file.</p>
|
||||
</div>
|
||||
<div class="paragraph">
|
||||
<p>Example: Access the <code>containers</code> package from the <code>haskellPackages</code> set in the nixpkgs repo.</p>
|
||||
<p>Example: Access the <code>extra</code> package from the <code>haskellPackages</code> set in the nixpkgs repo.</p>
|
||||
</div>
|
||||
<div class="listingblock">
|
||||
<div class="title">Script</div>
|
||||
|
|
@ -4573,36 +4534,24 @@ but you don’t want to bother writing a cabal file.</p>
|
|||
<span class="normal"> 7</span>
|
||||
<span class="normal"> 8</span>
|
||||
<span class="normal"> 9</span>
|
||||
<span class="normal">10</span>
|
||||
<span class="normal">11</span>
|
||||
<span class="normal">12</span>
|
||||
<span class="normal">13</span>
|
||||
<span class="normal">14</span>
|
||||
<span class="normal">15</span></pre></div></td><td class="code"><div><pre><span></span><span class="tok-o">#!</span><span class="tok-w"> </span><span class="tok-o">/</span><span class="tok-n">usr</span><span class="tok-o">/</span><span class="tok-n">bin</span><span class="tok-o">/</span><span class="tok-n">env</span><span class="tok-w"> </span><span class="tok-n">nix</span><span class="tok-o">-</span><span class="tok-n">shell</span>
|
||||
<span class="tok-o">#!</span><span class="tok-w"> </span><span class="tok-n">nix</span><span class="tok-o">-</span><span class="tok-n">shell</span><span class="tok-w"> </span><span class="tok-o">-</span><span class="tok-n">p</span><span class="tok-w"> </span><span class="tok-s">"haskellPackages.ghcWithPackages (p: [p.containers])"</span>
|
||||
<span class="normal">10</span></pre></div></td><td class="code"><div><pre><span></span><span class="tok-o">#!</span><span class="tok-w"> </span><span class="tok-o">/</span><span class="tok-n">usr</span><span class="tok-o">/</span><span class="tok-n">bin</span><span class="tok-o">/</span><span class="tok-n">env</span><span class="tok-w"> </span><span class="tok-n">nix</span><span class="tok-o">-</span><span class="tok-n">shell</span>
|
||||
<span class="tok-o">#!</span><span class="tok-w"> </span><span class="tok-n">nix</span><span class="tok-o">-</span><span class="tok-n">shell</span><span class="tok-w"> </span><span class="tok-o">-</span><span class="tok-n">p</span><span class="tok-w"> </span><span class="tok-s">"haskellPackages.ghcWithPackages (p: [p.extra])"</span>
|
||||
<span class="tok-o">#!</span><span class="tok-w"> </span><span class="tok-n">nix</span><span class="tok-o">-</span><span class="tok-n">shell</span><span class="tok-w"> </span><span class="tok-o">-</span><span class="tok-n">i</span><span class="tok-w"> </span><span class="tok-n">runghc</span>
|
||||
|
||||
<span class="tok-kr">import</span><span class="tok-w"> </span><span class="tok-nn">Data.Map</span>
|
||||
|
||||
<span class="tok-nf">m</span><span class="tok-w"> </span><span class="tok-ow">::</span><span class="tok-w"> </span><span class="tok-kt">Map</span><span class="tok-w"> </span><span class="tok-kt">String</span><span class="tok-w"> </span><span class="tok-kt">Int</span>
|
||||
<span class="tok-nf">m</span><span class="tok-w"> </span><span class="tok-ow">=</span><span class="tok-w"> </span><span class="tok-n">fromList</span><span class="tok-w"> </span><span class="tok-p">[(</span><span class="tok-s">"cats"</span><span class="tok-p">,</span><span class="tok-w"> </span><span class="tok-mi">3</span><span class="tok-p">),</span><span class="tok-w"> </span><span class="tok-p">(</span><span class="tok-s">"dogs"</span><span class="tok-p">,</span><span class="tok-w"> </span><span class="tok-mi">2</span><span class="tok-p">)]</span>
|
||||
<span class="tok-kr">import</span><span class="tok-w"> </span><span class="tok-nn">Data.List.Extra</span>
|
||||
|
||||
<span class="tok-nf">main</span><span class="tok-w"> </span><span class="tok-ow">::</span><span class="tok-w"> </span><span class="tok-kt">IO</span><span class="tok-w"> </span><span class="tok-nb">()</span>
|
||||
<span class="tok-nf">main</span><span class="tok-w"> </span><span class="tok-ow">=</span><span class="tok-w"> </span><span class="tok-kr">do</span>
|
||||
<span class="tok-w"> </span><span class="tok-kr">let</span><span class="tok-w"> </span><span class="tok-n">cats</span><span class="tok-w"> </span><span class="tok-ow">=</span><span class="tok-w"> </span><span class="tok-n">findWithDefault</span><span class="tok-w"> </span><span class="tok-mi">0</span><span class="tok-w"> </span><span class="tok-s">"cats"</span><span class="tok-w"> </span><span class="tok-n">m</span>
|
||||
<span class="tok-w"> </span><span class="tok-kr">let</span><span class="tok-w"> </span><span class="tok-n">dogs</span><span class="tok-w"> </span><span class="tok-ow">=</span><span class="tok-w"> </span><span class="tok-n">findWithDefault</span><span class="tok-w"> </span><span class="tok-mi">0</span><span class="tok-w"> </span><span class="tok-s">"dogs"</span><span class="tok-w"> </span><span class="tok-n">m</span>
|
||||
<span class="tok-w"> </span><span class="tok-kr">let</span><span class="tok-w"> </span><span class="tok-n">zebras</span><span class="tok-w"> </span><span class="tok-ow">=</span><span class="tok-w"> </span><span class="tok-n">findWithDefault</span><span class="tok-w"> </span><span class="tok-mi">0</span><span class="tok-w"> </span><span class="tok-s">"zebras"</span><span class="tok-w"> </span><span class="tok-n">m</span>
|
||||
<span class="tok-w"> </span><span class="tok-n">print</span><span class="tok-w"> </span><span class="tok-o">$</span><span class="tok-w"> </span><span class="tok-s">"I have "</span><span class="tok-w"> </span><span class="tok-o">++</span><span class="tok-w"> </span><span class="tok-n">show</span><span class="tok-w"> </span><span class="tok-n">cats</span><span class="tok-w"> </span><span class="tok-o">++</span><span class="tok-w"> </span><span class="tok-s">" cats, "</span><span class="tok-w"> </span><span class="tok-o">++</span><span class="tok-w"> </span><span class="tok-n">show</span><span class="tok-w"> </span><span class="tok-n">dogs</span><span class="tok-w"> </span><span class="tok-o">++</span><span class="tok-w"> </span><span class="tok-s">" dogs, and "</span><span class="tok-w"> </span><span class="tok-o">++</span><span class="tok-w"> </span><span class="tok-n">show</span><span class="tok-w"> </span><span class="tok-n">zebras</span><span class="tok-w"> </span><span class="tok-o">++</span><span class="tok-w"> </span><span class="tok-s">" zebras."</span>
|
||||
<span class="tok-w"> </span><span class="tok-n">print</span><span class="tok-w"> </span><span class="tok-o">$</span><span class="tok-w"> </span><span class="tok-n">lower</span><span class="tok-w"> </span><span class="tok-s">"ABCDE"</span>
|
||||
<span class="tok-w"> </span><span class="tok-n">print</span><span class="tok-w"> </span><span class="tok-o">$</span><span class="tok-w"> </span><span class="tok-n">upper</span><span class="tok-w"> </span><span class="tok-s">"XYZ"</span>
|
||||
</pre></div></td></tr></table></div></code></pre>
|
||||
</div>
|
||||
</div>
|
||||
<div class="literalblock">
|
||||
<div class="title">Output</div>
|
||||
<div class="content">
|
||||
<pre class="nowrap">this path will be fetched (141.61 MiB download, 1821.03 MiB unpacked):
|
||||
/nix/store/w6awqpzhn1pmfzql7ba5ar8pvs0yq5s2-ghc-9.8.4
|
||||
copying path '/nix/store/w6awqpzhn1pmfzql7ba5ar8pvs0yq5s2-ghc-9.8.4' from 'https://cache.nixos.org'...
|
||||
"I have 3 cats, 2 dogs, and 0 zebras."</pre>
|
||||
<pre class="nowrap">"abcde"
|
||||
"XYZ"</pre>
|
||||
</div>
|
||||
</div>
|
||||
</div>
|
||||
|
|
@ -4855,7 +4804,7 @@ In this example, we will access the <code>extra</code> package from the <code>ha
|
|||
<div class="paragraph">
|
||||
<p>For non-trivial Haskell development projects,
|
||||
it’s usually more convenient to use <code>haskell-flake</code> as described in <a href="#haskell-flake">Section 9.1.5, “The Nix flake”</a>,
|
||||
together with the high-level workflow described in <a href="#_development_workflows">Section 8.3, “Development workflows”</a>.</p>
|
||||
together with the <em>high-level workflow</em> described in <a href="#_development_workflows">Section 8.3, “Development workflows”</a>.</p>
|
||||
</div>
|
||||
</td>
|
||||
</tr>
|
||||
|
|
@ -5649,7 +5598,7 @@ Hello from your flake!</pre>
|
|||
</div>
|
||||
<div id="footer">
|
||||
<div id="footer-text">
|
||||
Last updated 2025-09-14 18:38:17 IST
|
||||
Last updated 2025-09-14 20:47:54 IST
|
||||
</div>
|
||||
</div>
|
||||
</body>
|
||||
|
|
|
|||
|
|
@ -44,7 +44,7 @@ $# cat flake.nix
|
|||
|
||||
If this is your first time seeing a flake definition, it probably looks
|
||||
intimidating.
|
||||
Flakes are written in the Nix language, introduced in an earlier chapter.
|
||||
Flakes are written in the Nix language, introduced in <<_the_nix_language_>>.
|
||||
However, you don't really need to know Nix to follow this example.
|
||||
For now, I'd like to focus on the inputs section.
|
||||
|
||||
|
|
|
|||
|
|
@ -3,9 +3,10 @@
|
|||
Now that we have a better understanding of the structure of `flake.nix`,
|
||||
let's have a look at the one we saw earlier, in the `hello-flake` repo.
|
||||
If you compare this flake definition to the colour-coded template
|
||||
presented in the previous section, most of it should look familiar.
|
||||
presented in <<_a_generic_flake>>, most of it should look familiar.
|
||||
|
||||
[source,nix,linenums]
|
||||
// don't use linenums because part of the file is omitted
|
||||
[source,nix]
|
||||
.flake.nix
|
||||
....
|
||||
{
|
||||
|
|
@ -48,7 +49,8 @@ additional development tools.
|
|||
Now let's look at the section I labeled `SOME UNFAMILIAR STUFF` and
|
||||
see what it does.
|
||||
|
||||
[source,nix,linenums,subs=quotes]
|
||||
// don't use linenums because part of the file is omitted
|
||||
[source,nix,subs=quotes]
|
||||
....
|
||||
packages = rec {
|
||||
hello = pkgs.stdenv.mkDerivation rec { ❶
|
||||
|
|
|
|||
|
|
@ -1,11 +1,10 @@
|
|||
= Hello, flake!
|
||||
|
||||
// TODO Need an intro explaining what flakes are. Move the "why flakes" section here.
|
||||
|
||||
Before learning to write Nix flakes, let's learn how to use them. I've
|
||||
created a simple example of a flake in this git
|
||||
https://codeberg.org/mhwombat/hello-flake[repository]. To run this
|
||||
flake, you don't need to install anything; simply run the command below.
|
||||
created a simple example of a flake in this git repository:
|
||||
https://codeberg.org/mhwombat/hello-flake.
|
||||
To run this flake, you don't need to install anything;
|
||||
simply run the command below.
|
||||
The first time you use a flake, Nix has to fetch and build it, which
|
||||
may take time. Subsequent invocations should be instantaneous.
|
||||
|
||||
|
|
|
|||
|
|
@ -99,7 +99,7 @@ $# cat hello-flake
|
|||
Let's test the modified script.
|
||||
|
||||
....
|
||||
$ ./hello-flake
|
||||
$ ./hello-flake # Won't work
|
||||
....
|
||||
|
||||
What went wrong? Remember that we are in a _development_ shell. Since
|
||||
|
|
@ -140,7 +140,7 @@ $ exit
|
|||
Let's try `nix run`.
|
||||
|
||||
....
|
||||
$ nix run
|
||||
$ nix run # Won't work
|
||||
....
|
||||
|
||||
What went wrong?
|
||||
|
|
@ -171,7 +171,7 @@ When you're packaging a program written in a more powerful language such as
|
|||
Haskell, Python, Java, C, C#, or Rust,
|
||||
the language build system will usually do all that is required
|
||||
to make the dependencies visible to the program at runtime.
|
||||
In this case, adding the dependency to `buildInputs` is sufficient.
|
||||
In that case, adding the dependency to `buildInputs` is sufficient.
|
||||
====
|
||||
|
||||
This time `nix run` works.
|
||||
|
|
|
|||
|
|
@ -70,7 +70,7 @@ Let's enter a shell with the Glasgow Haskell Compiler ("ghc") and try to run the
|
|||
....
|
||||
$# echo '$ nix shell nixpkgs#ghc'
|
||||
$# nix shell nixpkgs#ghc --command sh
|
||||
$ runghc Main.hs
|
||||
$ runghc Main.hs # Won't work
|
||||
....
|
||||
|
||||
The error message tells us that we need the module `Network.HostName`.
|
||||
|
|
@ -81,7 +81,7 @@ Let's exit that shell and try again, this time adding the `hostname` package.
|
|||
$# echo '$ exit'
|
||||
$# echo '$ nix shell nixpkgs#ghc nixpkgs#hostname'
|
||||
$# nix shell nixpkgs#ghc nixpkgs#hostname --command sh
|
||||
$ runghc Main.hs
|
||||
$ runghc Main.hs # Won't work
|
||||
....
|
||||
|
||||
That reason that failed is that we asked for the wrong package.
|
||||
|
|
@ -95,7 +95,7 @@ Let's try that again, with the correct package.
|
|||
$# echo '$ exit'
|
||||
$# echo '$ nix shell nixpkgs#ghc nixpkgs#haskellPackages.hostname'
|
||||
$# nix shell nixpkgs#ghc nixpkgs#haskellPackages.hostname --command sh
|
||||
$ runghc Main.hs
|
||||
$ runghc Main.hs # Won't work
|
||||
....
|
||||
|
||||
Now what's wrong?
|
||||
|
|
@ -121,10 +121,6 @@ $ runghc Main.hs
|
|||
|
||||
Success! Now we know the program works.
|
||||
|
||||
....
|
||||
$# echo '$ exit'
|
||||
....
|
||||
|
||||
== The cabal file
|
||||
|
||||
It's time to write a Cabal file for this program.
|
||||
|
|
|
|||
|
|
@ -101,7 +101,7 @@ We won't write `flake.nix` just yet.
|
|||
First we'll try building the package manually.
|
||||
(If you didn't run the `nix shell` command from <<python-nix-shell,earlier>>, do so now.)
|
||||
....
|
||||
$ python -m build
|
||||
$ python -m build # Won't work
|
||||
....
|
||||
|
||||
The missing module error happens because we don't have `build` available
|
||||
|
|
@ -198,11 +198,11 @@ $# cat flake.nix
|
|||
Let's try out the new flake.
|
||||
|
||||
....
|
||||
$ nix build
|
||||
$ nix build # Won't work
|
||||
....
|
||||
|
||||
Why can't it find `flake.nix`? Nix flakes only "`see`" files that are
|
||||
part of the repository. We need to add all of the important files to the
|
||||
Nix flakes only "`see`" files that are part of the repository.
|
||||
We need to add all of the important files to the
|
||||
repo before building or running the flake.
|
||||
|
||||
....
|
||||
|
|
|
|||
|
|
@ -19,7 +19,7 @@ $# cat flake.nix
|
|||
Here's a demonstration using the shell.
|
||||
|
||||
....
|
||||
$ cowsay "Moo!"
|
||||
$ cowsay "Moo!" # Won't work; dependency not available
|
||||
$# ../../../../../start-shell nix develop <<EOL
|
||||
$ cowsay "Moo!"
|
||||
$# EOL
|
||||
|
|
|
|||
60
source/recipes/devshell/nixpkg/tempwork/flake.lock
generated
Normal file
60
source/recipes/devshell/nixpkg/tempwork/flake.lock
generated
Normal file
|
|
@ -0,0 +1,60 @@
|
|||
{
|
||||
"nodes": {
|
||||
"flake-utils": {
|
||||
"inputs": {
|
||||
"systems": "systems"
|
||||
},
|
||||
"locked": {
|
||||
"lastModified": 1731533236,
|
||||
"narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
|
||||
"owner": "numtide",
|
||||
"repo": "flake-utils",
|
||||
"rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
|
||||
"type": "github"
|
||||
},
|
||||
"original": {
|
||||
"owner": "numtide",
|
||||
"repo": "flake-utils",
|
||||
"type": "github"
|
||||
}
|
||||
},
|
||||
"nixpkgs": {
|
||||
"locked": {
|
||||
"lastModified": 1757876592,
|
||||
"narHash": "sha256-P8XdKg87fR5PpCjIgMH+05PDwhdmlNrigsvChdHfyaw=",
|
||||
"owner": "NixOS",
|
||||
"repo": "nixpkgs",
|
||||
"rev": "5ad881b15fb2b63c2f127533ca59f840fcc24c3f",
|
||||
"type": "github"
|
||||
},
|
||||
"original": {
|
||||
"owner": "NixOS",
|
||||
"repo": "nixpkgs",
|
||||
"type": "github"
|
||||
}
|
||||
},
|
||||
"root": {
|
||||
"inputs": {
|
||||
"flake-utils": "flake-utils",
|
||||
"nixpkgs": "nixpkgs"
|
||||
}
|
||||
},
|
||||
"systems": {
|
||||
"locked": {
|
||||
"lastModified": 1681028828,
|
||||
"narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
|
||||
"owner": "nix-systems",
|
||||
"repo": "default",
|
||||
"rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
|
||||
"type": "github"
|
||||
},
|
||||
"original": {
|
||||
"owner": "nix-systems",
|
||||
"repo": "default",
|
||||
"type": "github"
|
||||
}
|
||||
}
|
||||
},
|
||||
"root": "root",
|
||||
"version": 7
|
||||
}
|
||||
20
source/recipes/devshell/nixpkg/tempwork/flake.nix
Normal file
20
source/recipes/devshell/nixpkg/tempwork/flake.nix
Normal file
|
|
@ -0,0 +1,20 @@
|
|||
{
|
||||
inputs = {
|
||||
nixpkgs.url = "github:NixOS/nixpkgs";
|
||||
flake-utils.url = "github:numtide/flake-utils";
|
||||
};
|
||||
|
||||
outputs = { self, nixpkgs, flake-utils }:
|
||||
flake-utils.lib.eachDefaultSystem (system:
|
||||
let
|
||||
pkgs = import nixpkgs { inherit system; };
|
||||
in
|
||||
{
|
||||
devShells = rec {
|
||||
default = pkgs.mkShell {
|
||||
packages = [ pkgs.cowsay ];
|
||||
};
|
||||
};
|
||||
}
|
||||
);
|
||||
}
|
||||
|
|
@ -3,7 +3,7 @@
|
|||
Occasionally you might want to run a short Haskell program that depends on a Haskell library,
|
||||
but you don't want to bother writing a cabal file.
|
||||
|
||||
Example: Access the `containers` package from the `haskellPackages` set in the nixpkgs repo.
|
||||
Example: Access the `extra` package from the `haskellPackages` set in the nixpkgs repo.
|
||||
|
||||
[source,haskell,linenums]
|
||||
.Script
|
||||
|
|
|
|||
|
|
@ -1,15 +1,10 @@
|
|||
#! /usr/bin/env nix-shell
|
||||
#! nix-shell -p "haskellPackages.ghcWithPackages (p: [p.containers])"
|
||||
#! nix-shell -p "haskellPackages.ghcWithPackages (p: [p.extra])"
|
||||
#! nix-shell -i runghc
|
||||
|
||||
import Data.Map
|
||||
|
||||
m :: Map String Int
|
||||
m = fromList [("cats", 3), ("dogs", 2)]
|
||||
import Data.List.Extra
|
||||
|
||||
main :: IO ()
|
||||
main = do
|
||||
let cats = findWithDefault 0 "cats" m
|
||||
let dogs = findWithDefault 0 "dogs" m
|
||||
let zebras = findWithDefault 0 "zebras" m
|
||||
print $ "I have " ++ show cats ++ " cats, " ++ show dogs ++ " dogs, and " ++ show zebras ++ " zebras."
|
||||
print $ lower "ABCDE"
|
||||
print $ upper "XYZ"
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue