<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta http-equiv="x-ua-compatible" content="ie=edge"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta name="generator" content="ExDoc v0.19.1"> <title>Logger.Formatter – Logger v1.7.2</title> <link rel="stylesheet" href="dist/app-240d7fc7e5.css" /> <link rel="canonical" href="https://hexdocs.pm/logger/v1.7/Logger.Formatter.html" /> <script src="dist/sidebar_items-17aeec0e2f.js"></script> </head> <body data-type="modules"> <script>try { if(localStorage.getItem('night-mode')) document.body.className += ' night-mode'; } catch (e) { }</script> <div class="main"> <button class="sidebar-button sidebar-toggle"> <span class="icon-menu" aria-hidden="true"></span> <span class="sr-only">Toggle Sidebar</span> </button> <button class="sidebar-button night-mode-toggle"> <span class="icon-theme" aria-hidden="true"></span> <span class="sr-only">Toggle Theme</span> </button> <section class="sidebar"> <a href="http://elixir-lang.org/docs.html" class="sidebar-projectLink"> <div class="sidebar-projectDetails"> <h1 class="sidebar-projectName"> Logger </h1> <h2 class="sidebar-projectVersion"> v1.7.2 </h2> </div> <img src="assets/logo.png" alt="Logger" class="sidebar-projectImage"> </a> <form class="sidebar-search" action="search.html"> <button type="submit" class="search-button"> <span class="icon-search" aria-hidden="true"></span> </button> <input name="q" type="text" id="search-list" class="search-input" placeholder="Search" aria-label="Search" autocomplete="off" /> </form> <ul class="sidebar-listNav"> <li><a id="extras-list" href="#full-list">Pages</a></li> <li><a id="modules-list" href="#full-list">Modules</a></li> </ul> <div class="gradient"></div> <ul id="full-list" class="sidebar-fullList"></ul> </section> <section class="content"> <div class="content-outer"> <div id="content" class="content-inner"> <h1> <small class="visible-xs">Logger v1.7.2</small> Logger.Formatter <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L3" title="View Source" class="view-source" rel="help"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> </h1> <section id="moduledoc"> <p>Conveniences for formatting data for logs.</p> <p>This module allows developers to specify a string that serves as template for log messages, for example:</p> <pre><code class="nohighlight makeup elixir"><span class="err">$</span><span class="n">time</span><span class="w"> </span><span class="err">$</span><span class="n">metadata</span><span class="p" data-group-id="1981602135-1">[</span><span class="err">$</span><span class="n">level</span><span class="p" data-group-id="1981602135-1">]</span><span class="w"> </span><span class="err">$</span><span class="n">message</span><span class="err">\</span><span class="n">n</span></code></pre> <p>Will print error messages as:</p> <pre><code class="nohighlight makeup elixir"><span class="mi">18</span><span class="p">:</span><span class="mi">43</span><span class="p">:</span><span class="mf">12.439</span><span class="w"> </span><span class="n">user_id</span><span class="o">=</span><span class="mi">13</span><span class="w"> </span><span class="p" data-group-id="9252357232-1">[</span><span class="n">error</span><span class="p" data-group-id="9252357232-1">]</span><span class="w"> </span><span class="nc">Hello</span><span class="err">\</span><span class="n">n</span></code></pre> <p>The valid parameters you can use are:</p> <ul> <li><code class="inline">$time</code> - the time the log message was sent </li> <li><code class="inline">$date</code> - the date the log message was sent </li> <li><code class="inline">$message</code> - the log message </li> <li><code class="inline">$level</code> - the log level </li> <li><code class="inline">$node</code> - the node that prints the message </li> <li><code class="inline">$metadata</code> - user controlled data presented in <code class="inline">"key=val key2=val2 "</code> format </li> <li><code class="inline">$levelpad</code> - sets to a single space if level is 4 characters long, otherwise set to the empty space. Used to align the message after level. </li> </ul> <p>Backends typically allow developers to supply such control strings via configuration files. This module provides <a href="#compile/1"><code class="inline">compile/1</code></a>, which compiles the string into a format for fast operations at runtime and <a href="#format/5"><code class="inline">format/5</code></a> to format the compiled pattern into an actual IO data.</p> <h2 id="module-metadata" class="section-heading"> <a href="#module-metadata" class="hover-link"><span class="icon-link" aria-hidden="true"></span></a> Metadata </h2> <p>Metadata to be sent to the logger can be read and written with the <a href="Logger.html#metadata/0"><code class="inline">Logger.metadata/0</code></a> and <a href="Logger.html#metadata/1"><code class="inline">Logger.metadata/1</code></a> functions. For example, you can set <code class="inline">Logger.metadata([user_id: 13])</code> to add user_id metadata to the current process. The user can configure the backend to choose which metadata it wants to print and it will replace the <code class="inline">$metadata</code> value.</p> </section> <section id="summary" class="details-list"> <h1 class="section-heading"> <a class="hover-link" href="#summary"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this section</span> </a> Summary </h1> <div class="summary-types summary"> <h2> <a href="#types">Types</a> </h2> <div class="summary-row"> <div class="summary-signature"> <a href="#t:pattern/0">pattern()</a> </div> </div> <div class="summary-row"> <div class="summary-signature"> <a href="#t:time/0">time()</a> </div> </div> </div> <div class="summary-functions summary"> <h2> <a href="#functions">Functions</a> </h2> <div class="summary-row"> <div class="summary-signature"> <a href="#compile/1">compile(pattern)</a> </div> <div class="summary-synopsis"><p>Compiles a format string into a data structure that <a href="#format/5"><code class="inline">format/5</code></a> can handle</p> </div> </div> <div class="summary-row"> <div class="summary-signature"> <a href="#format/5">format(config, level, msg, timestamp, metadata)</a> </div> <div class="summary-synopsis"><p>Takes a compiled format and injects the level, timestamp, message, and metadata keyword list and returns a properly formatted string</p> </div> </div> <div class="summary-row"> <div class="summary-signature"> <a href="#format_date/1">format_date(arg)</a> </div> <div class="summary-synopsis"><p>Formats date as chardata</p> </div> </div> <div class="summary-row"> <div class="summary-signature"> <a href="#format_time/1">format_time(arg)</a> </div> <div class="summary-synopsis"><p>Formats time as chardata</p> </div> </div> <div class="summary-row"> <div class="summary-signature"> <a href="#prune/1">prune(binary)</a> </div> <div class="summary-synopsis"><p>Prunes non-valid UTF-8 codepoints</p> </div> </div> </div> </section> <section id="types" class="details-list"> <h1 class="section-heading"> <a class="hover-link" href="#types"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this section</span> </a> Types </h1> <div class="types-list"> <div class="detail" id="t:pattern/0"> <div class="detail-header"> <a href="#t:pattern/0" class="detail-link" title="Link to this type"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this type</span> </a> <span class="signature">pattern()</span> <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L44" class="view-source" rel="help" title="View Source"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> <div class="specs"> <pre>pattern() :: :date | :level | :levelpad | :message | :metadata | :node | :time</pre> </div> </div> <section class="docstring"> </section> </div> <div class="detail" id="t:time/0"> <div class="detail-header"> <a href="#t:time/0" class="detail-link" title="Link to this type"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this type</span> </a> <span class="signature">time()</span> <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L43" class="view-source" rel="help" title="View Source"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> <div class="specs"> <pre>time() :: {{1970..10000, 1..12, 1..31}, {0..23, 0..59, 0..59, 0..999}}</pre> </div> </div> <section class="docstring"> </section> </div> </div> </section> <section id="functions" class="details-list"> <h1 class="section-heading"> <a class="hover-link" href="#functions"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this section</span> </a> Functions </h1> <div class="detail" id="compile/1"> <div class="detail-header"> <a href="#compile/1" class="detail-link" title="Link to this function"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this function</span> </a> <span class="signature">compile(pattern)</span> <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L91" class="view-source" rel="help" title="View Source"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> <div class="specs"> <pre>compile(<a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">binary</a>() | nil) :: [<a href="#t:pattern/0">pattern</a>() | <a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">binary</a>()]</pre> <pre>compile(pattern) :: pattern when pattern: {<a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">module</a>(), function :: <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">atom</a>()}</pre> </div> </div> <section class="docstring"> <p>Compiles a format string into a data structure that <a href="#format/5"><code class="inline">format/5</code></a> can handle.</p> <p>Check the module doc for documentation on the valid parameters that will be interpolated in the pattern. If you pass <code class="inline">nil</code> as the pattern, the pattern defaults to:</p> <pre><code class="nohighlight makeup elixir"><span class="s">"</span><span class="se">\n</span><span class="s">$time $metadata[$level] $levelpad$message</span><span class="se">\n</span><span class="s">"</span></code></pre> <p>If you want to customize formatting through a custom formatter, you can pass a <code class="inline">{module, function}</code> tuple as the <code class="inline">pattern</code>.</p> <pre><code class="nohighlight makeup elixir"><span class="gp unselectable">iex> </span><span class="nc">Logger.Formatter</span><span class="o">.</span><span class="n">compile</span><span class="p" data-group-id="0134175263-1">(</span><span class="s">"$time $metadata [$level] $message</span><span class="se">\n</span><span class="s">"</span><span class="p" data-group-id="0134175263-1">)</span><span class="w"> </span><span class="p" data-group-id="0134175263-2">[</span><span class="ss">:time</span><span class="p">,</span><span class="w"> </span><span class="s">" "</span><span class="p">,</span><span class="w"> </span><span class="ss">:metadata</span><span class="p">,</span><span class="w"> </span><span class="s">" ["</span><span class="p">,</span><span class="w"> </span><span class="ss">:level</span><span class="p">,</span><span class="w"> </span><span class="s">"] "</span><span class="p">,</span><span class="w"> </span><span class="ss">:message</span><span class="p">,</span><span class="w"> </span><span class="s">"</span><span class="se">\n</span><span class="s">"</span><span class="p" data-group-id="0134175263-2">]</span><span class="w"> </span><span class="gp unselectable">iex> </span><span class="nc">Logger.Formatter</span><span class="o">.</span><span class="n">compile</span><span class="p" data-group-id="0134175263-3">(</span><span class="p" data-group-id="0134175263-4">{</span><span class="nc">MyLoggerFormatter</span><span class="p">,</span><span class="w"> </span><span class="ss">:format</span><span class="p" data-group-id="0134175263-4">}</span><span class="p" data-group-id="0134175263-3">)</span><span class="w"> </span><span class="p" data-group-id="0134175263-5">{</span><span class="nc">MyLoggerFormatter</span><span class="p">,</span><span class="w"> </span><span class="ss">:format</span><span class="p" data-group-id="0134175263-5">}</span></code></pre> </section> </div> <div class="detail" id="format/5"> <div class="detail-header"> <a href="#format/5" class="detail-link" title="Link to this function"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this function</span> </a> <span class="signature">format(config, level, msg, timestamp, metadata)</span> <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L150" class="view-source" rel="help" title="View Source"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> <div class="specs"> <pre>format( {<a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">atom</a>(), <a href="https://hexdocs.pm/elixir/typespecs.html#basic-types">atom</a>()} | [<a href="#t:pattern/0">pattern</a>() | <a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">binary</a>()], <a href="Logger.html#t:level/0">Logger.level</a>(), <a href="Logger.html#t:message/0">Logger.message</a>(), <a href="#t:time/0">time</a>(), <a href="https://hexdocs.pm/elixir/typespecs.html#built-in-types">keyword</a>() ) :: <a href="https://hexdocs.pm/elixir/IO.html#t:chardata/0">IO.chardata</a>()</pre> </div> </div> <section class="docstring"> <p>Takes a compiled format and injects the level, timestamp, message, and metadata keyword list and returns a properly formatted string.</p> <h2 id="format/5-examples" class="section-heading"> <a href="#format/5-examples" class="hover-link"><span class="icon-link" aria-hidden="true"></span></a> Examples </h2> <pre><code class="nohighlight makeup elixir"><span class="gp unselectable">iex> </span><span class="n">pattern</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">Logger.Formatter</span><span class="o">.</span><span class="n">compile</span><span class="p" data-group-id="9385852679-1">(</span><span class="s">"[$level] $message"</span><span class="p" data-group-id="9385852679-1">)</span><span class="w"> </span><span class="gp unselectable">iex> </span><span class="n">timestamp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p" data-group-id="9385852679-2">{</span><span class="p" data-group-id="9385852679-3">{</span><span class="mi">1977</span><span class="p">,</span><span class="w"> </span><span class="mi">01</span><span class="p">,</span><span class="w"> </span><span class="mi">28</span><span class="p" data-group-id="9385852679-3">}</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9385852679-4">{</span><span class="mi">13</span><span class="p">,</span><span class="w"> </span><span class="mi">29</span><span class="p">,</span><span class="w"> </span><span class="mi">00</span><span class="p">,</span><span class="w"> </span><span class="mi">000</span><span class="p" data-group-id="9385852679-4">}</span><span class="p" data-group-id="9385852679-2">}</span><span class="w"> </span><span class="gp unselectable">iex> </span><span class="n">formatted</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nc">Logger.Formatter</span><span class="o">.</span><span class="n">format</span><span class="p" data-group-id="9385852679-5">(</span><span class="n">pattern</span><span class="p">,</span><span class="w"> </span><span class="ss">:info</span><span class="p">,</span><span class="w"> </span><span class="s">"hello"</span><span class="p">,</span><span class="w"> </span><span class="n">timestamp</span><span class="p">,</span><span class="w"> </span><span class="p" data-group-id="9385852679-6">[</span><span class="p" data-group-id="9385852679-6">]</span><span class="p" data-group-id="9385852679-5">)</span><span class="w"> </span><span class="gp unselectable">iex> </span><span class="nc">IO</span><span class="o">.</span><span class="n">chardata_to_string</span><span class="p" data-group-id="9385852679-7">(</span><span class="n">formatted</span><span class="p" data-group-id="9385852679-7">)</span><span class="w"> </span><span class="s">"[info] hello"</span></code></pre> </section> </div> <div class="detail" id="format_date/1"> <div class="detail-header"> <a href="#format_date/1" class="detail-link" title="Link to this function"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this function</span> </a> <span class="signature">format_date(arg)</span> <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L120" class="view-source" rel="help" title="View Source"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> <div class="specs"> <pre>format_date({1970..10000, 1..12, 1..31}) :: <a href="https://hexdocs.pm/elixir/IO.html#t:chardata/0">IO.chardata</a>()</pre> </div> </div> <section class="docstring"> <p>Formats date as chardata.</p> </section> </div> <div class="detail" id="format_time/1"> <div class="detail-header"> <a href="#format_time/1" class="detail-link" title="Link to this function"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this function</span> </a> <span class="signature">format_time(arg)</span> <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L112" class="view-source" rel="help" title="View Source"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> <div class="specs"> <pre>format_time({0..23, 0..59, 0..59, 0..999}) :: <a href="https://hexdocs.pm/elixir/IO.html#t:chardata/0">IO.chardata</a>()</pre> </div> </div> <section class="docstring"> <p>Formats time as chardata.</p> </section> </div> <div class="detail" id="prune/1"> <div class="detail-header"> <a href="#prune/1" class="detail-link" title="Link to this function"> <span class="icon-link" aria-hidden="true"></span> <span class="sr-only">Link to this function</span> </a> <span class="signature">prune(binary)</span> <a href="https://github.com/elixir-lang/elixir/blob/v1.7.2/lib/logger/lib/logger/formatter.ex#L59" class="view-source" rel="help" title="View Source"> <span class="icon-code" aria-hidden="true"></span> <span class="sr-only">View Source</span> </a> <div class="specs"> <pre>prune(<a href="https://hexdocs.pm/elixir/IO.html#t:chardata/0">IO.chardata</a>()) :: <a href="https://hexdocs.pm/elixir/IO.html#t:chardata/0">IO.chardata</a>()</pre> </div> </div> <section class="docstring"> <p>Prunes non-valid UTF-8 codepoints.</p> <p>Typically called after formatting when the data cannot be printed.</p> </section> </div> </section> <footer class="footer"> <p> <span class="line"> Built using <a href="https://github.com/elixir-lang/ex_doc" title="ExDoc" target="_blank" rel="help noopener">ExDoc</a> (v0.19.1), </span> <span class="line"> designed by <a href="https://twitter.com/dignifiedquire" target="_blank" rel="noopener" title="@dignifiedquire">Friedel Ziegelmayer</a>. </span> </p> </footer> </div> </div> </section> </div> <script src="dist/app-a0c90688fa.js"></script> </body> </html>