Running shell script using NSTask in Mac OS - objective-c

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;
}
});
}