Querying node attributes

This example shows how to get graph node by node name and how to query node attributes.
The input file is assumed to be in GraphViz DOT language.

For the graph shown below the program produces the following output:


Node: a, shape: box, color: red
Node: b, shape: hexagon, color: green
Node: c, shape: circle, color: blue

 1 #pragma package ".."
 2 #include "chagraph.h"
 3 #include <stdlib.h>
 4 
 5 int main(int argc, char *argv[])
 6 {
 7   Agraph_t *g;
 8   Agnode_t *n;
 9 
10   if (argc < 2) {
11     printf("Usage:  %s file\n"
12            "   file -- file in GraphViz dot format\n",
13            argv[0]);
14     exit(EXIT_FAILURE);
15   }
16   FILE *f = fopen(argv[1], "r");
17   g = agread(f, 0);
18   fclose(f);
19 
20   char *node_name[] = {"a", "b", "c"};
21   int i;
22   for (i=0; i<3; i++) {
23     n = agnode(g, node_name[i], FALSE);
24     if (n != 0) {
25       printf("Node: %s, shape: %s, color: %s\n", 
26              agnameof(n), 
27              agget(n, "shape"), 
28              agget(n, "color"));
29     }
30   }
31   
32   agclose(g); 
33   return 0;
34 }

Code description

23: Search graph for a node with given name. The third argument indicates the behaviour when node is not found. If FALSE agnode return 0, if TRUE agnode adds new node to the graph
32: Close graph and free memeory allocated for it