Clean up the unique_ptr using a custom deleter

Author: Martin D. Weinberg

exputil/getmd5sum.cc

@@ -5,17 +5,28 @@
 #include <memory>
 #include <algorithm>
 
+// Define the custom deleter
+struct PcloseDeleter {
+  void operator()(FILE* f) const {
+    if (f) pclose(f);
+  }
+};
+
 std::string get_md5sum(const std::string& filename)
 {
+  // Check if md5sum is available on the system
+  if (std::system("which md5sum > /dev/null 2>&1") != 0) {
+    throw std::runtime_error("md5sum command not found. Please ensure it is installed and in your PATH.");
+  }
+
   // Command to execute: md5sum <filename>
   std::string command = "md5sum " + filename;
   std::array<char, 128> buffer;
   std::string result = "";
 
   // Use popen to execute the command and read its output
   // "r" mode opens the pipe for reading
-  std::unique_ptr<FILE, decltype(&pclose)>
-    pipe(popen(command.c_str(), "r"), pclose);
+  std::unique_ptr<FILE, PcloseDeleter> pipe(popen(command.c_str(), "r"));
   if (!pipe) {
     throw std::runtime_error("popen() failed!");
   }