Iteration over all graph edges

This example shows how one can read graph from a file and iterate over all graph edges. For each edge visited its label is printed.
The input file is assumed to be in GraphViz DOT language.

Sample undirected graph for this example is shown in the figure below:

 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   Agedge_t *e;
10 
11   if (argc < 2) {
12     printf("Usage:  %s file\n"
13            "   file -- file in GraphViz dot format\n",
14            argv[0]);
15     exit(EXIT_FAILURE);
16   }
17   FILE *f = fopen(argv[1], "r");
18   g = agread(f, 0);
19   fclose(f);
20 
21   for (n = agfstnode(g); n; n = agnxtnode(n)) {
22     for (e = agfstout(n); e; e = agnxtout(e)) {
23       printf("edge: %s\n", agget(e, "label"));
24     }
25   } 
26  
27   agclose(g); 
28   return 0;
29 }

Code description

21-25: Iterate over all edges of graph (directed or undirected) and print their labels.
27: close graph and free memeory allocated for it