Iterate all edges and src, target and weight

mm.c

#include <igraph.h>
#include <stdio.h>

void custom_warning_handler (const char *reason, const char *file,
               int line, int igraph_errno) {
    printf("Warning: %s\n", reason);
}

int main(int argc, char* argv[])
{
  char * in_graph_fn;
  char * out_graph_fn;

  if (argc < 3) {
    printf("[ERROR] usage: mm-writer in_graph_fn out_graph_fn\n");
    exit(-1);
  }
  else {
    in_graph_fn = &argv[1][0];
    out_graph_fn = &argv[2][0];
  }

  igraph_t g;
  long int i;
  igraph_integer_t size;
  igraph_vs_t vs; // Vertex selector
  igraph_vit_t vit; // Vertex iterator

  igraph_error_handler_t* oldhandler;
  igraph_warning_handler_t* oldwarnhandler;
  int result;
  FILE *ifile, *ofile;

  ifile = fopen(in_graph_fn, "r");
  if (ifile == 0) {
    return 10;
  }

  igraph_read_graph_graphml(&g, ifile, 0);
  fclose(ifile);
  igraph_to_directed(&g, IGRAPH_TO_DIRECTED_ARBITRARY);

  printf("The graph stats:\n");
  printf("Vertices: %li\n", (long int) igraph_vcount(&g));
  printf("Edges: %li\n", (long int) igraph_ecount(&g));
  printf("Directed: %i\n", (int) igraph_is_directed(&g));

  igraph_i_set_attribute_table(&igraph_cattribute_table);

  if ( igraph_cattribute_has_attr(&g, IGRAPH_ATTRIBUTE_EDGE, "weight") ) { // SEG FAULT here :/
    printf("Got it\n");
  }
  else {
    printf("Don't!\n");
  }

  igraph_vit_destroy(&vit);
  igraph_vs_destroy(&vs);
  igraph_destroy(&g);

  return 0;
}