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<title>strong_conn(1) - Find the strongly connected components of a directed graph</title>
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<a href="#NAME">NAME</a>
<a href="#SYNOPSIS">SYNOPSIS</a>
<a href="#DESCRIPTION">DESCRIPTION</a>
<a href="#PARAMETERS">PARAMETERS</a>
<a href="#OUTPUT">OUTPUT</a>
<a href="#EXAMPLES">EXAMPLES</a>
<a href="#SEE-ALSO">SEE ALSO</a>
<a href="#REFERENCES">REFERENCES</a>
<a href="#AUTHORS">AUTHORS</a>
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<ol class='man-decor man-head man head'>
<li class='tl'>strong_conn(1)</li>
<li class='tc'>www.complex-networks.net</li>
<li class='tr'>strong_conn(1)</li>
</ol>
<h2 id="NAME">NAME</h2>
<p class="man-name">
<code>strong_conn</code> - <span class="man-whatis">Find the strongly connected components of a directed graph</span>
</p>
<h2 id="SYNOPSIS">SYNOPSIS</h2>
<p><code>strong_conn</code> <var>graph_in</var> [SHOW]</p>
<h2 id="DESCRIPTION">DESCRIPTION</h2>
<p><code>strong_conn</code> finds the strongly connected components of the directed
graph given as input using the Kosaraju-Sharir algorithm, and prints
the size of each of them. If the optional second parameter <code>SHOW</code> is
provided, the program dumps on output also the list of nodes belonging
to each component.</p>
<h2 id="PARAMETERS">PARAMETERS</h2>
<dl>
<dt><var>graph_in</var></dt><dd><p> input graph (edge list) if equal to <code>-</code> (dash), read the edge list
from STDIN.</p></dd>
<dt class="flush">SHOW</dt><dd><p> If the (optional) second parameter is equal to <code>SHOW</code>, the program
will dump on output the list of all the nodes belonging to each
strongly connected component.</p></dd>
</dl>
<h2 id="OUTPUT">OUTPUT</h2>
<p><code>strong_conn</code> prints on the standard output the size of all the
strongly connected components of the directed graph given as input,
one per line:</p>
<pre><code> size_1
size_2
size_3
.....
</code></pre>
<p>where <code>size_1</code> is the size of the first component, <code>size_2</code> is the
size of the second component, and so on. Notice that the sizes are not
sorted. If <code>SHOW</code> is given, the program shows the list of nodes
belonging to each strongly connected component, in the format:</p>
<pre><code>size_1: node_1 node_2 node_3 ...
size_2: node_1 node_2 node_3 ...
</code></pre>
<h2 id="EXAMPLES">EXAMPLES</h2>
<p>The following command:</p>
<pre><code> $ strong_conn web-NotreDame.net
53968
1
1
1
1
1
1
....
$
</code></pre>
<p>shows on output the size of the strongly connected component of the
graph <code>web-NotreDame.net</code> (the NotreDame WWW data set), in no particular
order. In this case the graph has 203609 strongly connected
components, most of them containing only 1 isolated node. If we want
to know who are the nodes belonging to each connected component, we
run:</p>
<pre><code> $ strong_conn web-NotreDame.net SHOW
53968: 0 1 3 4 5 6 7 8.....
..... 325727 325728
1: 351
1: 350
1: 2209
1: 2208
1: 2206
1: 10609
....
$
</code></pre>
<p>It is better to save the output of <code>strong_conn</code> into a file, e.g. by
using:</p>
<pre><code> $ strong_conn web-NotreDame.net SHOW > web-NotreDame.net_scc
</code></pre>
<h2 id="SEE-ALSO">SEE ALSO</h2>
<p><span class="man-ref">components<span class="s">(1)</span></span>, <span class="man-ref">node_components<span class="s">(1)</span></span>, <span class="man-ref">largest_component<span class="s">(1)</span></span></p>
<h2 id="REFERENCES">REFERENCES</h2>
<ul>
<li><p>V. Latora, V. Nicosia, G. Russo, "Complex Networks: Principles,
Methods and Applications", Chapter 6, Cambridge University Press
(2017)</p></li>
<li><p>V. Latora, V. Nicosia, G. Russo, "Complex Networks: Principles,
Methods and Applications", Appendix 8, Cambridge University Press
(2017)</p></li>
</ul>
<h2 id="AUTHORS">AUTHORS</h2>
<p>(c) Vincenzo 'KatolaZ' Nicosia 2009-2017 <code><v.nicosia@qmul.ac.uk></code>.</p>
<ol class='man-decor man-foot man foot'>
<li class='tl'>www.complex-networks.net</li>
<li class='tc'>September 2017</li>
<li class='tr'>strong_conn(1)</li>
</ol>
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