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Clarify stderr behavior of modules

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Michael DeHaan
2012-04-27 01:39:15 -04:00
parent aed5414cb6
commit d049d425e6
14 changed files with 39 additions and 19 deletions
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moduledev.html
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@@ -176,9 +176,9 @@ a module that just outputs the current time.</p>
<p>We are going to use Python here but any language is possible. Only File I/O and outputing to standard
out are required. So, bash, C++, clojure, Python, Ruby, whatever you want
is fine.</p>
<p>It&#8217;s obvious that you would never really need to build a module to set the system time,
the &#8216;command&#8217; module could already be used to do this. However, it makes for a decent example.
Reading the modules that come with ansible (linked above) is a great way to learn how to write
<p>So, here&#8217;s an example. You would never really need to build a module to set the system time,
the &#8216;command&#8217; module could already be used to do this. Though we&#8217;re going to make one.</p>
<p>Reading the modules that come with ansible (linked above) is a great way to learn how to write
modules. Keep in mind, though, that some modules in ansible&#8217;s source tree are internalisms,
so look at <cite>service</cite> or <cite>yum</cite>, and don&#8217;t stare too close into things like <cite>async_wrapper</cite> or
you&#8217;ll turn to stone. Nobody ever executes async_wrapper directly.</p>
@@ -331,6 +331,12 @@ json isn&#8217;t in the Python standard library until 2.5.:</p>
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<p>Because the output is supposed to be valid JSON. Except that&#8217;s not quite true,
but we&#8217;ll get to that later.</p>
<p>Further, modules must not output anything on stderr, even if the JSON returned
out stdout is valid. This is due to the internals of our SSH library, more or less.</p>
<p>If a module returns stderr or otherwise fails to produce valid JSON, the actual output
will still be shown in Ansible, however, but the command will not succeed.</p>
<p>Always use the hacking/test-module script when developing modules and it will warn
you about these kind of things.</p>
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<div class="section" id="conventions">
<h2>Conventions<a class="headerlink" href="#conventions" title="Permalink to this headline"></a></h2>
@@ -396,7 +402,7 @@ Stop by the mailing list to inquire about requirements.</p>
<p class="pull-right"><a href="#">Back to top</a></p>
<p>
&copy; Copyright 2012 Michael DeHaan.<br/>
Last updated on Apr 25, 2012.<br/>
Last updated on Apr 27, 2012.<br/>
Created using <a href="http://sphinx.pocoo.org/">Sphinx</a> 1.0.8.<br/>
</p>
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