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Re: NSTask waitForDataInBackgroundAndNotify and waitUntilExit


On May 12, 2008, at 23:04, Shawn Erickson wrote:

Your placement of waitUntilExit is blocking the runloop which needs to
be running to service the background notifications you requested.


Ah ...I see. That makes sense.

If
you want async behavior then you cannot wait on the task (at least not
in the way you are currently attempting).

Review the following code example...

http://developer.apple.com/samplecode/Moriarity/listing5.html 

Thanks for the pointer.

Well, actually I was just using waitForDataInBackgroundAndNotify trying to understand the options.

Looking at http://www.cocoadev.com/index.pl?NSTaskWaitUntilExit I would have thought this should work

	NSTask *task = [[NSTask alloc] init];
	[task setLaunchPath:path];
	[task setArguments:args];
	
	NSPipe *outPipe = [NSPipe pipe];
	[task setStandardOutput:outPipe];
	NSFileHandle *outFile = [outPipe fileHandleForReading];

	NSPipe *errPipe = [NSPipe pipe];
	[task setStandardError:errPipe];
	NSFileHandle *errFile = [errPipe fileHandleForReading];	

	[task launch];

    NSData *data;

while((data = [outFile availableData]) && [data length]) {
[output appendString:[NSString stringWithCString:[data bytes] encoding: NSUTF8StringEncoding]];
}

while((data = [errFile availableData]) && [data length]) {
[error appendString:[NSString stringWithCString:[data bytes] encoding: NSUTF8StringEncoding]];
}

	[task waitUntilExit];

While it works just fine for executing "ps" even the most simple shell script:

    #!/bin/sh
    echo "out"
    echo "err" >&2
    exit 0

gets stuck. No matter whether I call it directly or via "/bin/sh -c pathtoscript". The first call to "availableData" just blocks. Looking at the documentation ("if no data is available, the method blocks") I am a little surprised as there should be some data available.

Any further suggestions or comments?

cheers
--
Torsten
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References: 
 >NSTask waitForDataInBackgroundAndNotify and waitUntilExit (From: Torsten Curdt <email@hidden>)
 >Re: NSTask waitForDataInBackgroundAndNotify and waitUntilExit (From: "Shawn Erickson" <email@hidden>)



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