Fix results perm check

Rdutil.cc

@@ -27,12 +27,17 @@
 // class declaration
 #include "Rdutil.hh"
 
+bool
+Rdutil::trywritetofile(const std::string& filename)
+{
+  return !!std::ofstream(filename);
+}
+
 int
 Rdutil::printtofile(const std::string& filename) const
 {
   // open a file to print to
-  std::ofstream f1;
-  f1.open(filename.c_str(), std::ios_base::out);
+  std::ofstream f1(filename);
   if (!f1.is_open()) {
     std::cerr << "could not open file \"" << filename << "\"\n";
     return -1;

Rdutil.hh

@@ -24,6 +24,13 @@ public:
   {
   }
 
+  /**
+   * opens the given file for writing and closes it again.
+   * @param filename
+   * @return true if it went ok
+   */
+  static bool trywritetofile(const std::string& filename);
+
   /**
    * print file names to a file, with extra information.
    * @param filename

rdfind.cc

@@ -91,6 +91,17 @@ main(int narg, const char* argv[])
   global_options = &o;
   dirlist.setcallbackfcn(&report);
 
+  if (o.makeresultsfile) {
+    // make sure the results file can be opened, before doing all potentially
+    // lengthy work. in case of permission problems, it is not fun to find out
+    // only after the fact. see https://github.com/pauldreik/rdfind/issues/128
+    if (!Rdutil::trywritetofile(o.resultsfile)) {
+      std::cerr << "could not write to results file \"" << o.resultsfile
+                << "\"\n";
+      std::exit(EXIT_FAILURE);
+    }
+  }
+
   // now loop over path list and add the files
 
   // done with arguments. start parsing files and directories!