Prototyping:

- Opening a GNU Tar file via comand line argument
- Parse itemname, itemtype and itemsize in bytes of first item in Tar archive
- Print those to stdout.

main.cpp

@@ -1,26 +1,75 @@
 #include <iostream>
 #include <fstream>
 #include <string>
+#include <vector>
+#include <cmath>
 
-int main() {
-    std::ifstream datei("test.tar", std::ios::binary);
-    if(!datei)
-        std::cout << "Fehler beim Oeffnen der Datei" << std::endl;
 
-    int headersize = 512;
-    char* headbuffer = new char[headersize];
 
-    datei.read(headbuffer, headersize);
-    std::string filename{};
-    for (int i = 0; i <= 99; i++)
-    {
-        if (headbuffer[i] != '\0')
-            filename.push_back(headbuffer[i]);
+
+int main(int argc, char** argv) {
+
+    // Trivial check for arguments. Errorprone and has to be changed.
+    if (argc < 2) {
+        std::cout << "Please enter filename" << std::endl;
+        return 9;
     }
-    std::cout << filename << std::endl;
+    // Getting name from argument lists on startup. Trivial and errorprone. Placeholder for now.
+    std::string archiveFilename(argv[1]);
 
-    std::string filename2(&headbuffer[0], 100);
-    std::cout << filename2 << std::endl;
+    //Open tar File.
+    std::ifstream datei(archiveFilename, std::ios::binary);
+    if(!datei)
+        std::cout << "Error opening file" << std::endl;
+
+    // Tar spec is working with continous 512 byte size blocks. Header is 512 bytes.
+    int headersize = 512;
+
+    //Read header of first item in tar archive
+    char* headbuffer = new char[headersize];
+    datei.read(headbuffer, headersize);
+
+    // Read name of the next item
+    std::string itemname(&headbuffer[0], 100);
+    std::erase(itemname, '\0');
+
+    // Read type of item
+    std::string itemtype{};
+    switch (headbuffer[156]){
+        case '0': case '\0':
+            itemtype = "FILE";
+            break;
+        case '1':
+            itemtype = "HARDLINK";
+            break;
+        case '2':
+            itemtype = "SYMLINK";
+            break;
+        case '5':
+            itemtype = "DIRECTORY";
+            break;
+        default:
+            itemtype = "OTHER";
+            break;
+    }
+
+
+
+
+    // Read size of the next file
+    long double filesize{};
+    int power = 10;
+    std::string asciifilesize(&headbuffer[124], 11);
+    for (auto i : asciifilesize) {
+        int value = i - '0';
+        filesize += value * std::pow(8,power);
+        power--;
+    }
+
+    //Printing to stdout
+    std::cout << itemname << std::endl;
+    std::cout << itemtype << std::endl;
+    std::cout << filesize << " Bytes" << std::endl;
 
     return 0;
 }