Qfyilyi

I need to modify some C code that currently reads two columns of data from an ascii file, so that it can check to see if a third column is provided and if a third column is found, will read the third column.

The relevant snippet of code is currently:

    struct forestListElement * forestList = malloc(nTrees*sizeof(struct forestListElement));

    // skip first line                                                                                                                                                      

    fgets(line,800,file);

    cnt = 0;

    while( fgets(line,sizeof(line),file) !=NULL)  {

            pch = strtok(line," ");

            forestList[cnt].treeRootId =atoll(pch);

            pch = strtok(NULL," ");

            forestList[cnt].forestId = atoll(pch);

            cnt++;

    }

This snippet is looping over a file that currently has two columns of data (two IDs in long format). But I would like to modify the code so that after reading the first two columns it checks to see if a third column exists and, if it does, read a weight from that column. If the third column does not exist, set the weight to 1. I would like to modify the code to something like:

    struct forestListElement * forestList = malloc(nTrees*sizeof(struct forestListElement));

    // skip first line                                                                                                                                                      

    fgets(line,800,file);

    cnt = 0;

    while( fgets(line,sizeof(line),file) !=NULL)  {

            pch = strtok(line," ");

            forestList[cnt].treeRootId =atoll(pch);

            pch = strtok(NULL," ");

            forestList[cnt].forestId = atoll(pch);

            forestList[cnt].forestWeight = 1.0;

            if(<check if third column exists>){   \ <-- what do I put here? 

                  pch = strtok(NULL," ");

                  forestList[cnt].forestWeight = atof(pch);

            }

            cnt++;

    }

What do I need to include in the if-statement?

Apologies if this is a simple task, but I am not familiar with C and am struggling to know what to search for on Google!

Thanks.