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+components(1) -- Find the connected components of a graph
+======
+
+## SYNOPSIS
+
+`components` <graph_in> [SHOW]
+
+## DESCRIPTION
+
+`components` finds the connected components of the undirected graph
+given as input using the Depth-First Search algorithm, and prints the
+size of each of them. If the optional second parameter `SHOW` is
+provided, the program dumps on output also the list of nodes belonging
+to each component.
+
+## PARAMETERS
+
+* <graph_in>:
+    input graph (edge list) if equal to `-` (dash), read the edge list
+    from STDIN.
+
+
+* SHOW: 
+    If the (optional) second parameter is equal to `SHOW`, the program
+    will dump on output the list of all the nodes belonging to each
+    connected component.
+
+## OUTPUT
+
+`components` prints on the standard output the size of all the
+connected components of the undirected graph given as input, one per
+line:
+
+    size_1
+    size_2
+    size_3
+    .....
+
+where `size_1` is the size of the first component, `size_2` is the
+size of the second component, and so on. Notice that the sizes are not
+sorted.  If `SHOW` is given, the program shows the list of nodes
+belonging to each component, in the format:
+
+    size_1: node_1 node_2 node_3 ...
+    size_2: node_1 node_2 node_3 ...
+    
+## EXAMPLES
+
+The following command:
+
+          $ components er_1000_5000.txt 
+          1000
+          $
+
+shows on output the size of the only connected component of the graph
+`er_1000_5000.txt`. In this case the graph has only one connected
+component (it is a super-critical Erdos-Renyi random graph with 1000
+nodes and 5000 edges). A more interesting example can be obtained
+using the graph `er_1000_2000.txt`:
+
+          $ components er_1000_2000.txt 
+          985
+          1
+          1
+          1
+		  1
+          1
+          1
+          1
+	      1
+	      1
+	      1
+	      1
+	      1
+	      1
+	      1
+	      1
+          $
+
+In this case, the graph has 16 connected components: one of those
+components contains 985 nodes, while the other 15 components consist
+of isolated nodes. If we want to know who are the nodes belonging to
+each connected component, we run:
+
+          $ components er_1000_2000.txt SHOW
+          985: 0 1 2 3 4 5 6 7 8 9 10 11 12.....
+          ...
+          1: 63
+          1: 75
+          1: 218
+          1: 222
+          1: 368
+          1: 398
+          1: 441
+          1: 566
+          1: 572
+          1: 663
+          1: 715
+          1: 756
+          1: 863
+          1: 883
+          1: 917
+          $
+
+If we run:
+
+          $ components er_1000_2000.txt SHOW > er_1000_2000.txt_components
+
+the result of `components` will be saved in the file
+`er_1000_2000.txt_components`.
+
+## SEE ALSO 
+
+strong_conn(1), node_components(1), largest_component(1)
+
+
+## REFERENCES
+
+* V\. Latora, V. Nicosia, G. Russo, "Complex Networks: Principles,
+  Methods and Applications", Chapter 3, Cambridge University Press
+  (2017)
+
+* V\. Latora, V. Nicosia, G. Russo, "Complex Networks: Principles,
+  Methods and Applications", Appendix 8, Cambridge University Press
+  (2017)
+
+
+## AUTHORS
+
+(c) Vincenzo 'KatolaZ' Nicosia 2009-2017 `<v.nicosia@qmul.ac.uk>`.