How to get shell script output in an OS X Application - macos

Question

I have an OS X App, it makes a call to shell script using this:
#implementation ViewController {
NSTask *task;
NSPipe *pipe;
}
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
[self runCommand:[[NSBundle mainBundle] pathForResource:#"Test" ofType:#"command"] arguments:nil];
}
- (void)runCommand:(NSString *)cmd arguments:(NSArray *)args {
if (task)
{
[task interrupt];
}
else
{
task = [[NSTask alloc] init];
[task setLaunchPath:cmd];
[task setArguments:args];
pipe = [[NSPipe alloc] init];
[task setStandardOutput:pipe];
NSFileHandle* fh = [pipe fileHandleForReading];
[task launch];
[fh readInBackgroundAndNotify];
}
}
#end
The shell script Test.command has output text which will be displayed in Terminal window when you execute it in Terminal, but is there a way to retrieve this output in my OS X App and display it into a text view?

Answer 1

You need to observe the notification event fired by the task. The order in which you register the observer and launch the command is also important. Try something like:
{
task = [[NSTask alloc] init];
[task setLaunchPath:cmd];
[task setArguments:args];
pipe = [[NSPipe alloc] init];
[task setStandardOutput:pipe];
// Observe events before launching the task, otherwise the execution
// might end before we get the chance to register the observer.
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(didCompleteReadingFileHandle:)
name:NSFileHandleReadCompletionNotification
object:[[task standardOutput] fileHandleForReading]];
// Make it start reading before launching.
[[pipe fileHandleForReading] readInBackgroundAndNotify];
// Launch it.
[task launch];
}
- (void)didCompleteReadingFileHandle:(NSNotification *)notification
{
NSData *data = [[notification userInfo]
objectForKey:NSFileHandleNotificationDataItem];
// Do something with data...
}