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<title>s6-portable-utils: the s6-hiercopy program</title>
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<a href="index.html">s6-portable-utils</a><br />
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<h1> The <tt>s6-hiercopy</tt> program </h1>
<p>
<tt>s6-hiercopy</tt> copies a directory structure recursively.
</p>
<h2> Interface </h2>
<pre>
s6-hiercopy <em>source</em> <em>destination</em>
</pre>
<ul>
<li> <tt>s6-hiercopy</tt> recursively copies <em>source</em> to
<em>destination</em>, which is created if it doesn't exist.
The permissions are preserved. The owner and group are preserved
if the user is the superuser. </li>
<li> It exits 0 on success and 111 on temporary failure. </li>
</ul>
<h2> Notes </h2>
<ul>
<li> Copying files and browsing through directories is one of Unix's
weakest points, and <tt>s6-hiercopy</tt> is not meant to work around
the problem; it's only a quick hack that I needed to boot my embedded
platform. I originally planned to write the ultimate <tt>cp</tt> utility,
portable and reliable and featureful and everything - while needing
approximately a hundred times less resources than GNU <tt>cp</tt> does,
of course. But I eventually dropped the idea: it's impossible to
design, much less write, such a utility. Notably,
you cannot make it reliable because Unix's set of filesystem
management primitives is just too weak. It lacks a lot of atomic
operations, and filesystem transactions. As a result, <tt>s6-hiercopy</tt>
is a walking race condition and should <strong>absolutely not</strong>
be considered instant when used in a multitasking environment.
But then, <tt>cp</tt> shouldn't either. </li>
<li> There is no standard way of creating device nodes on a
filesystem, so any <tt>cp</tt>-like utility is inherently
non-portable. Fortunately, most systems still agree on the non-portable usages of
<a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/mknod.html">mknod
specification</a>, so things should work in practice. Consequently,
the s6-hiercopy utility has been moved from
<a href="//skarnet.org/software/s6-linux-utils/">s6-linux-utils</a>
to s6-portable-utils. </li>
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