Support directories (instead of crashing)

src/main/cpp/Makefile

@@ -1,10 +1,10 @@
 default: tiv
 
 tiv.o: tiv.cpp CImg.h
-	g++ -std=c++11 -Wall -fexceptions -O2 -c tiv.cpp -o tiv.o
+	g++ -std=c++17  -Wall -fpermissive -fexceptions -O2 -c tiv.cpp -o tiv.o
 
 tiv : tiv.o
-	g++ tiv.o -o tiv -pthread -s
+	g++ tiv.o -o tiv -lstdc++fs -pthread -s
 
 install: tiv
 	cp tiv /usr/local/bin/tiv

src/main/cpp/tiv.cpp

@@ -5,6 +5,7 @@
 #include <string>
 #include <vector>
 #include <sys/ioctl.h>
+#include <experimental/filesystem>
 
 #define cimg_display 0
 #include "CImg.h"
@@ -434,10 +435,19 @@ int main(int argc, char* argv[]) {
       emit_usage();
     } else if (arg[0] == '-') {
       std::cerr << "Unrecognized argument: " << arg << std::endl;
+    } else {
+      if (std::experimental::filesystem::is_directory(arg)) {
+         for (auto & p : std::experimental::filesystem::directory_iterator(arg)) {
+           if (std::experimental::filesystem::is_regular_file(p.path())) {
+             file_names.push_back(p.path().string());
+           }
+	 }
       } else {
         file_names.push_back(arg);
       }
     }
+  }
+
 
   if (mode == FULL_SIZE || (mode == AUTO && file_names.size() == 1)) {
     for (unsigned int i = 0; i < file_names.size(); i++) {