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    <title>s6-portable-utils: the s6-tai64ndiff program</title>
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<a href="//skarnet.org/software/">Software</a><br />
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<h1> The s6-tai64ndiff program </h1>

<p>
s6-tai64ndiff acts as a filter, reading from stdin and writing to stdout.
It expects every line of its input to begin with a
<a href="//skarnet.org/software/skalibs/libstddjb/tai.html#timestamp">TAI64N
timestamp</a>. It replaces this timestamp with a prefix showing the time
difference between this line and the previous line.
</p>

<h2> Interface </h2>

<pre>
     s6-tai64ndiff
</pre>

<ul>
 <li> s6-tai64ndiff exits 0 when it sees the end of stdin. If there's an
unfinished line, s6-tai64ndiff processes it and writes it before exiting. </li>
 <li> The prefix it prints is of the form <tt>[ <em>seconds</em>.<em>microseconds</em> ]</tt>,
in decimal. It can be interpreted as a fixed-point decimal number of seconds that
elapsed between the timestamp on the previous line and the timestamp on the
current line. </li>
 <li> If the difference isn't defined, <em>seconds</em> and <em>microseconds</em>
are just whitespace. The difference is not defined on the first line of stdin or
on non-timestamped lines. Following non-timestamped lines, the difference may not
be accurate. </li>
</ul>

<h2> Notes </h2>

<ul>
 <li> The typical use case of s6-tai64ndiff is to read files that have
been filtered through <a href="s6-tai64n.html">s6-tai64n</a>, or log files
that have been produced by <a href="s6-log.html">s6-log</a> with the <tt>t</tt>
directive. </li>
 <li> The difference is a signed number. Negative numbers probably indicate
a backwards clock jump, which is a bad thing to have on a system. </li>
</ul>

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