Add intelligent output format selection for EXI encoding

- Terminal output: Display hex string for easy copying/viewing
- File redirection: Write binary data for proper file creation
- Auto-detect output destination using fstat() and isatty()
- Clean terminal display without debug messages
- Support both viewing (hex) and file creation (binary) workflows

Usage examples:
- ./enhanced_exi_viewer -encode file.xml          # Shows hex string
- ./enhanced_exi_viewer -encode file.xml > out.exi  # Creates binary file

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

enhanced_exi_viewer.c

@@ -2,6 +2,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
+#include <unistd.h>
+#include <sys/stat.h>
 
 /* EXI codec headers */
 #include "iso1EXIDatatypes.h"
@@ -997,9 +999,14 @@ int main(int argc, char *argv[]) {
             free(xml_content);
             return -1;
         }
+        // Show encoding info only when redirecting to file (keeps terminal output clean)
+        struct stat stat_buf_debug;
+        int is_file_redirect = (fstat(fileno(stdout), &stat_buf_debug) == 0 && S_ISREG(stat_buf_debug.st_mode));
+        if (is_file_redirect) {
             fprintf(stderr, "XML parsing successful\\n");
             fprintf(stderr, "SessionID length: %d\\n", iso1Doc.V2G_Message.Header.SessionID.bytesLen);
             fprintf(stderr, "CurrentDemandReq_isUsed: %s\\n", iso1Doc.V2G_Message.Body.CurrentDemandReq_isUsed ? "true" : "false");
+        }
         
         free(xml_content);
         
@@ -1017,8 +1024,29 @@ int main(int argc, char *argv[]) {
             return -1;
         }
         
-        // Write EXI data to stdout (binary)
+        // Check if output is redirected (for Windows/MINGW compatibility)
+        // Use environment variable approach or check for redirection
+        char* term = getenv("TERM");
+        int use_hex_output = (term != NULL) || isatty(fileno(stdout));
+        
+        // Also check if user specifically wants binary output by checking for redirection
+        struct stat stat_buf;
+        if (fstat(fileno(stdout), &stat_buf) == 0 && S_ISREG(stat_buf.st_mode)) {
+            use_hex_output = 0; // Regular file, use binary
+        }
+        
+        if (use_hex_output) {
+            // Terminal output: show hex string
+            printf("Encoded EXI data (%zu bytes):\n", pos);
+            for(size_t i = 0; i < pos; i++) {
+                printf("%02X", buffer[i]);
+                if ((i + 1) % 32 == 0) printf("\n");
+            }
+            if (pos % 32 != 0) printf("\n");
+        } else {
+            // Redirected output: write binary data
             fwrite(buffer, 1, pos, stdout);
+        }
         return 0;
     }