Getting data from the nstask - communicating with command line - objective c

Question

I know how to send data to the task:

NSData *charlieSendData = [[charlieImputText stringValue] dataUsingEncoding:NSUTF8StringEncoding];
[[[task standardInput] fileHandleForWriting] writeData:charlieSendData];

But how do I get what the task responds with??

Elijah

Answer 1

Give an NSPipe or an NSFileHandle as the task's standardOutput, and read from that.

NSTask * list = [[NSTask alloc] init];
[list setLaunchPath:@"/bin/ls"];
[list setCurrentDirectoryPath:@"/"];

NSPipe * out = [NSPipe pipe];
[list setStandardOutput:out];

[list launch];
[list waitUntilExit];
[list release];

NSFileHandle * read = [out fileHandleForReading];
NSData * dataRead = [read readDataToEndOfFile];
NSString * stringRead = [[[NSString alloc] initWithData:dataRead encoding:NSUTF8StringEncoding] autorelease];
NSLog(@"output: %@", stringRead);

Note that if you use a pipe, you have to worry about the pipe filling up. If you provide an NSFileHandle instead, the task can output all it wants without you having to worry about losing any, but you also get the overhead of having to write the data out to disk.

Answer 2

Swift 3 solution, you can implement a closure that accepts a FileHandle

let process = Process()
process.launchPath = launchPath
process.arguments = arguments

let stdOut = Pipe()
process.standardOutput = stdOut
let stdErr = Pipe()
process.standardError = stdErr

let handler =  { (file: FileHandle!) -> Void in
  let data = file.availableData
  guard let output = NSString(data: data, encoding: String.Encoding.utf8.rawValue)
    else { return}

  print(output.components(separatedBy: "\n").first!)
}

stdErr.fileHandleForReading.readabilityHandler = handler
stdOut.fileHandleForReading.readabilityHandler = handler

process.terminationHandler = { (task: Process?) -> () in
  stdErr.fileHandleForReading.readabilityHandler = nil
  stdOut.fileHandleForReading.readabilityHandler = nil
}

process.launch()
process.waitUntilExit()