Hello,
I need to develop a tool which processes stdin as it arrives from its parent
process. The following code works as expected when it is in invoked with no
stdin, that is…
Air2:Debug jk$ ./MyTool
But if I pipe some initial stdin to it, like this
Air2:Debug jk$ echo Hello | ./MyTool
after the initial notification and processing of “Hello”, the
notification-handling block infinitely receives repeated, different
notifications, for which -availableData returns an empty data object.
I can’t understand and cannot work around it. Why am I getting infinitely
repeated notifications when there is no data available?
Thanks!
Jerry
int main(int argc, const char * argv[]) {
@autoreleasepool {
/* -[NSFileManager waitForDataInBackgroundAndNotify] docs say I need
an "active run loop". I don't know what they mean by "active".
Maybe this will help (it didn't). */
NSDate* verySoon = [NSDate dateWithTimeIntervalSinceNow:0.01] ;
[[NSRunLoop mainRunLoop] runUntilDate:verySoon] ;
NSFileHandle* input = [NSFileHandle fileHandleWithStandardInput] ;
[input waitForDataInBackgroundAndNotify] ;
NSNotificationCenter* dc = [NSNotificationCenter defaultCenter] ;
[dc addObserverForName:NSFileHandleDataAvailableNotification
object:input
queue:nil
usingBlock:^(NSNotification* note) {
NSFileHandle* input ;
input = [NSFileHandle fileHandleWithStandardInput] ;
NSData* data = [input availableData] ;
NSLog(@"Got noted of %ld bytes", (long)[data length]) ;
if ([data length] > 0) {
NSFileHandle* output ;
output = [NSFileHandle fileHandleWithStandardOutput] ;
[output writeData:[NSData dataWithBytes:"--> "
length:4]] ;
[output writeData:data] ;
}
[input waitForDataInBackgroundAndNotify] ;
}] ;
/*SSYDBL*/ NSLog(@"Running run loop") ;
[[NSRunLoop mainRunLoop] run] ;
}
return 0 ;
}
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