Here's a post that I found useful:
http://dev.notoptimal.net/2007/04/nstasks-nspipes-and-deadlocks-when.html
Dave, not sure what you mean here. NSPipe uses NSFileHandle. Does using an
NSFileHandle directly change things somehow? If so, why? I think this is an
avenue I haven't explored; once I (finally) figured out the right magic
incantations to get things to work reliably with NSPipe, I now recycle that
code everywhere I need an NSTask :->.
Ben Haller
McGill University
On 2010-11-27, at 11:48 AM, Dave DeLong wrote:
> The way I get around this is to use an NSFileHandle for standard out instead
> of an NSPipe. It's a bit less efficient, but slightly more convenient.
>
> Dave
>
> Sent from my iPhone
>
> On Nov 27, 2010, at 7:59 AM, Ben Haller <bhcocoa...@sticksoftware.com> wrote:
>
>> On 2010-11-26, at 7:33 AM, gMail.com wrote:
>>
>>> Hi, I can properly unzip a zip file launching a NSTask with /usr/bin/unzip
>>> The task saves the unzipped file to the disk, then a I read the unzipped
>>> file in a NSData. Well. My question is:
>>> Can I do the same job without saving the unzipped file to the disk?
>>>
>>> I have tried to set the standard output to a pipe - which works well with
>>> other tasks - but here it doesn't work. The task never exits. Here's the
>>> wrong code:
>>>
>>> NSTask *unzip = [[[NSTask alloc] init] autorelease];
>>> [unzip setLaunchPath:@"/usr/bin/unzip"];
>>> [unzip setArguments:[NSArray arrayWithObjects:@"-p", zipfile,
>>> @"filetounzip", nil]];
>>>
>>> NSPipe *aPipe = [NSPipe pipe];
>>> [unzip setStandardOutput:aPipe];
>>> [unzip launch];
>>> [unzip waitUntilExit];
>>>
>>> if([unzip terminationStatus] == noErr){
>>> dictData = [NSMutableData data];
>>> while((dataOut = [aPipe availableData]) && [dataOut length]){
>>> [dictData appendData:dataOut];
>>> }
>>> }
>>
>> If I recall correctly, the problem is likely to be your use of
>> -waitUntilExit. That API should apparently have a large red label on it
>> ("Warnin', lark's vomit!") since everybody wants to use it this way. The
>> problem is that the task's output pipe fills up because it isn't being
>> serviced, and then things get locked up. You need to go with asynchronous
>> reads to service the pipe as output gets stuffed into it. There should be
>> lots of examples of this on this list, now that you know what to look for.
>>
>> What would be great would be a new call, along the lines of
>> -dataFromWaitingUntilExit or some such, that does all this for you, since
>> this is so commonly what people want to do.
>>
>> Ben Haller
>> McGill University
>>
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