Prevent overwrite by default and can be overriden with cmdline option

ct2foam.C

@@ -166,6 +166,13 @@ std::string ofReactionString (const std::shared_ptr<Cantera::Reaction> r)
 }
 
 
+bool is_file_exist(const std::string &fileName)
+{
+    std::ifstream infile(fileName);
+    return infile.good();
+}
+
+
 int main(int argc, char *argv[])
 {
 
@@ -179,9 +186,9 @@ int main(int argc, char *argv[])
     std::ofstream fthermo;
     std::ofstream frxn;
 
-
     options.add_options()
         ("name", "Name of ideal gas mix in CTI file", cxxopts::value(sgas))
+        ("w,overwrite", "Overwrite exsisting files")
         ("h,help", "print help message")
         ;
 
@@ -218,9 +225,26 @@ int main(int argc, char *argv[])
 
     Cantera::IdealGasMix gas_(scti, sgas);
 
-    fthermo.open(sthermo);
+    bool overwrite = result["overwrite"].as<bool>();
+
+    if (is_file_exist(sthermo) && (!overwrite))
+    {
+        throw std::system_error(EEXIST, std::system_category(), sthermo);
+    }
+    else
+    {
+        fthermo.open(sthermo);
+    }
+
+    if (is_file_exist(srxn) && (!overwrite))
+    {
+        throw std::system_error(EEXIST, std::system_category(), srxn);
+    }
+    else
+    {
+        frxn.open(srxn);
+    }
 
-    frxn.open(srxn);
 
     // Thermo Part =============================================================