Example of writing to cout or filename

ostream.cc

#include <fstream>
#include <iostream>

void prin_vecvec(vecvec_t & vvs, const char *sep, const char *recsep, const char *filename )
{
        
        std::ofstream ofs;
        bool use_file = strlen(filename);
        if(use_file) ofs.open(filename, std::ofstream::out);
        ostream &os = use_file ? ofs : cout ;

        string ssep = string(sep);
        int i;
        for(i=0; i< vvs.size(); i++) {
                vector<string> v = vvs[i];
                int j, len;
                len = v.size();
                if(len == 0) continue;
                for(j=0; j<len; j++) {
                        os << v[j];
                        if(j+1<len) os << ssep;
                }
                if(len>0) os << recsep ;
        }

        if(use_file) ofs.close();
}