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POHow to run NSTask with multiple commands
 

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  1. POHow to run NSTask with multiple commands
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    <p>I'm trying to make a NSTask running a command like this:</p> <blockquote> <p>ps -clx | grep 'Finder' | awk '{print $2}'</p> </blockquote> <p>Here is my method</p> <pre><code>- (void) processByName:(NSString*)name { NSTask *task1 = [[NSTask alloc] init]; NSPipe *pipe1 = [NSPipe pipe]; [task1 waitUntilExit]; [task1 setLaunchPath: @"/bin/ps"]; [task1 setArguments: [NSArray arrayWithObjects: @"-clx", nil]]; [task1 setStandardOutput: pipe1]; NSTask *task2 = [[NSTask alloc] init]; NSPipe *pipe2 = [NSPipe pipe]; [task2 setLaunchPath: @"/usr/bin/grep"]; [task2 setArguments: [NSArray arrayWithObjects: @"'Finder'", nil]]; [task2 setStandardInput:pipe1]; [task2 setStandardOutput: pipe2]; NSTask *task3 = [[NSTask alloc] init]; NSPipe *pipe3 = [NSPipe pipe]; [task3 setLaunchPath: @"/usr/bin/grep"]; [task3 setArguments: [NSArray arrayWithObjects: @"'{print $2}'", nil]]; [task3 setStandardInput:pipe2]; [task3 setStandardOutput: pipe3]; NSFileHandle *file = [pipe3 fileHandleForReading]; [task1 launch]; [task2 launch]; [task3 launch]; NSData *data; data = [file readDataToEndOfFile]; NSString *string; string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding]; NSLog(@"Result: %@", string); } </code></pre> <p>But the result is just</p> <blockquote> <p>Result: </p> </blockquote> <p>What am I doing wrong?</p> <p><strong>EDIT</strong></p> <pre><code>- (void) processByName:(NSString*)name { NSTask *task1 = [[NSTask alloc] init]; NSPipe *pipe1 = [NSPipe pipe]; [task1 waitUntilExit]; [task1 setLaunchPath: @"/bin/ps"]; [task1 setArguments: [NSArray arrayWithObjects: @"-clx", nil]]; [task1 setStandardOutput: pipe1]; NSTask *task2 = [[NSTask alloc] init]; NSPipe *pipe2 = [NSPipe pipe]; [task2 setLaunchPath: @"/usr/bin/grep"]; [task2 setArguments: [NSArray arrayWithObjects: @"'Finder'", nil]]; [task2 setStandardInput:pipe1]; [task2 setStandardOutput: pipe2]; NSTask *task3 = [[NSTask alloc] init]; NSPipe *pipe3 = [NSPipe pipe]; [task3 setLaunchPath: @"/usr/bin/grep"]; [task3 setArguments: [NSArray arrayWithObjects: @"'{print $2}'", nil]]; [task3 setStandardInput:pipe2]; [task3 setStandardOutput: pipe3]; NSFileHandle *file = [pipe3 fileHandleForReading]; [task1 launch]; [task2 launch]; [task3 launch]; [[NSNotificationCenter defaultCenter] addObserverForName:NSTaskDidTerminateNotification object:task3 queue:nil usingBlock:^(NSNotification* notification){ NSData * data = [file readDataToEndOfFile]; NSString * string; string = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding]; NSLog(@"Result: %@", string); }]; } </code></pre>
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