Running shell script using NSTask in Mac OS

Question

I have written a shell script and the purpose of that script is to capture packet using TCPDUMP and write that capture packet to .pcap file

Script is: TCPDumpScript.sh

echo "peter" | sudo -S tcpdump -i rv0 -n -s 0 -w dumpfile.pcap tcp

I am launching (TCPDumpScript.sh) using NSTask. Getting following output

tcpdump: WARNING: rv0: That device doesn't support promiscuous mode (BIOCPROMISC: Operation not supported on socket) tcpdump: WARNING: rv0: no IPv4 address assigned tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on rv0, link-type PKTAP (Packet Tap), capture size 65535 bytes

Problem 1: Using NSTask. "dumpfile.pcap" is being created. but when I run the same script using Terminal, its being created with desired captured packets.

Problem 2: Whenever making changes in TCPDumpScript.sh and then launching script using NSTask. I am getting following error "launch path not accessible"

But I do via terminal chmod +x TCPDumpScript.sh

Then I am able to launch this script without any error using NSTask.

So, my question is Can't I create file (Problem 1) "dumpfile.pcap" using NSTask ? And Do I always require to run permission change command on script file (Problem 2) ?

Please guide me.

• (void)runScript:(NSArray*)arguments {

  dispatch_queue_t taskQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0); dispatch_async(taskQueue, ^{

  self.isRunning = YES;
  
  @try {
  
      NSString *path  = [NSString stringWithFormat:@"%@", [[NSBundle mainBundle] pathForResource:@"TcpDumpScript" ofType:@"sh"]];         
      self.buildTask            = [[NSTask alloc] init];
      self.buildTask.launchPath = path;
      self.buildTask.arguments  = arguments;
  
      // Output Handling
      self.outputPipe               = [[NSPipe alloc] init];
      self.buildTask.standardOutput = self.outputPipe;
  
      [[self.outputPipe fileHandleForReading] waitForDataInBackgroundAndNotify];
  
      [[NSNotificationCenter defaultCenter] addObserverForName:NSFileHandleDataAvailableNotification object:[self.outputPipe fileHandleForReading] queue:nil usingBlock:^(NSNotification *notification){
  
          NSData *output = [[self.outputPipe fileHandleForReading] availableData];
          NSString *outStr = [[NSString alloc] initWithData:output encoding:NSUTF8StringEncoding];
  
          dispatch_sync(dispatch_get_main_queue(), ^{
              self.outPutTxt.string = [self.outPutTxt.string stringByAppendingString:[NSString stringWithFormat:@"\n%@", outStr]];
              // Scroll to end of outputText field
              NSRange range;
              range = NSMakeRange([self.outPutTxt.string length], 0);
              [self.outPutTxt scrollRangeToVisible:range];
          });
  
          [[self.outputPipe fileHandleForReading] waitForDataInBackgroundAndNotify];
      }];
  
      [self.buildTask launch];
  
      [self.buildTask waitUntilExit];
  }
  @catch (NSException *exception) {
      NSLog(@"Problem Running Task: %@", [exception description]);
  }
  @finally {
      [self.Start setEnabled:YES];
      [self.spinner stopAnimation:self];
      self.isRunning = NO;
  }
  

  }); }