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PONSTask/NSPipe read from Unix command
 

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    <p>I am writing a Cocoa application which needs to execute a UNIX program and read its output, line by line, as they are produced. I set up a NSTask and NSPipe as such:</p> <pre><code>task = [[NSTask alloc] init]; pipe = [NSPipe pipe]; [task setStandardOutput:pipe]; //... later ... [task setArguments:...]; [task setLaunchPath:@"..."]; [task launch]; handle = [[task fileHandleForReading] retain]; </code></pre> <p>The command does not terminate until the program tells it to do so with <code>[task terminate]</code>. I have tried several methods of reading from the handle, such as <code>-readInBackgroundAndNotify</code>, <code>while([(data = [handle availableData]) length] &gt; 0)</code>, and <code>-waitForDataInBackgroundAndNotify</code>, but the pipe never seems to yield any data. Is there some way I can "poke" the <code>NSTask</code> or <code>NSPipe</code> to flush the data through?</p> <p><strong>EDIT</strong>: with <code>-readInBackgroundAndNotify</code>:</p> <pre><code>[handle readInBackgroundAndNotify]; notification_block_t handlerBlock = ^(NSNotification *notification) { NSData *data = [[notification userInfo] objectForKey: NSFileHandleNotificationDataItem]; /*... do stuff ...*/ [self addNotification: handle block: handlerBlock]; }; [self addNotification: handler block: handlerBlock]; //... - (void)addNotification:(id)handle block:(notification_block_t)block { [[NSNotificationCenter defaultCenter] addObserverForName: NSFileHandleReadCompletionNotification object: handle queue: [NSOperationQueue mainQueue] usingBlock: block]; } </code></pre> <p>with <code>-waitForDataInBackgroundAndNotify</code>:</p> <pre><code>[handle waitForDataInBackgroundAndNotify]; notification_block_t handlerBlock = ^(NSNotification *notification) { NSData *data = [handle availableData]; /*... do stuff ...*/ }; [self addNotification: handler block: handlerBlock]; </code></pre> <p>with <code>while</code> loop:</p> <pre><code>[self startProcessingThread: handle]; //... - (void)startProcessingThread:(NSFileHandle *)handle { [[NSOperationQueue mainQueue] addOperation: [[[NSInvocationOperation alloc] initWithTarget: self selector: @selector(dataLoop:) object: handle] autorelease]]; } - (void)dataLoop:(NSFileHandle *)handle { NSData *data; while([(data = [handle availableData]) length] &gt; 0) { /*... do stuff ...*/ } } </code></pre> <p><strong>EDIT 2</strong>: The arguments are set as follows (the command is <code>tshark</code>):</p> <pre><code>NSArray *cmd = [NSArray arrayWithObjects:@"-R", @"http.request", @"-Tfields", @"-Eseparator='|'", @"-ehttp.host", @"-ehttp.request.method", @"-ehttp.request.uri", nil]; cmd = [[cmd arrayByAddingObjectsFromArray:[self.ports map:^(id arg1, NSUInteger idx) { return [NSString stringWithFormat:@"-d tcp.port==%d,http", [arg1 intValue]]; }]] arrayByAddingObject:[@"dst " stringByAppendingString: [self.hosts componentsJoinedByString:@" or dst "]]]; [self.tsharktask setArguments:cmd]; </code></pre>
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    1. USActorclavilis
    1. USActorclavilis
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      1. VTUpMod
    1. COPost all your code (e.g. how you defined the NSFileHandleDataAvailableNotification).
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      1. USMichele Percich
    2. CO`typedef (^notification_block_t)(NSNotification *);`, of course.
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      1. USActorclavilis
 

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