sends lib log to /dev/null in posix and added option (v) to reactivate

There in an error handling and messaging inside

utils/nfc-mfclassic.c

@@ -54,6 +54,12 @@
 #include <string.h>
 #include <ctype.h>
 
+#ifndef _WIN32
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#endif
+
 #include <nfc/nfc.h>
 
 #include "mifare.h"
@@ -571,7 +577,11 @@ static void
 print_usage(const char *pcProgramName)
 {
  printf("Usage: ");
+ #ifndef _WIN32
+ printf("%s f|r|R|w|W a|b u|U<01ab23cd> <dump.mfd> [<keys.mfd> [f] [v]]\n", pcProgramName);
+ #else
  printf("%s f|r|R|w|W a|b u|U<01ab23cd> <dump.mfd> [<keys.mfd> [f]]\n", pcProgramName);
+ #endif
  printf(" f|r|R|w|W - Perform format (f) or read from (r) or unlocked read from (R) or write to (w) or unlocked write to (W) card\n");
  printf(" *** format will reset all keys to FFFFFFFFFFFF and all data to 00 and all ACLs to default\n");
  printf(" *** unlocked read does not require authentication and will reveal A and B keys\n");
@@ -582,7 +592,9 @@ print_usage(const char *pcProgramName)
  printf(" <dump.mfd> - MiFare Dump (MFD) used to write (card to MFD) or (MFD to card)\n");
  printf(" <keys.mfd> - MiFare Dump (MFD) that contain the keys (optional)\n");
  printf(" f - Force using the keyfile even if UID does not match (optional)\n");
-
+ #ifndef _WIN32
+ printf(" v - Sends libnfc log output to console (optional)\n");
+ #endif
  printf("Examples: \n\n");
  printf(" Read card to file, using key A:\n\n");
  printf(" %s r a u mycard.mfd\n\n", pcProgramName);
@@ -706,6 +718,21 @@ main(int argc, const char *argv[])
  tag_uid = NULL;
  }
 
+ #ifndef _WIN32
+ // Send noise from lib to /dev/null
+ bool verbose = false;
+ if (argv[7]) {
+ if (strcmp(argv[7], "v") == 0) verbose = true;
+ } else {
+ if (strcmp(argv[6], "v") == 0) verbose = true;
+ }
+ if (!verbose) {
+ int fd = open("/dev/null", O_WRONLY);
+ dup2(fd, 2);
+ close(fd);
+ }
+ #endif
+
  if (atAction == ACTION_USAGE) {
  print_usage(argv[0]);
  exit(EXIT_FAILURE);