On Mon, Aug 13, 2012, at 04:38 PM, Ken Thomases wrote:
> On Aug 13, 2012, at 5:42 PM, Kyle Sluder wrote:
>
> > On Mon, Aug 13, 2012, at 02:17 PM, Charlie Dickman wrote:
> >> I'm trying to get the output from a vm_stat command using the following
> >> code. My app hangs in the [vmRead availableData] call as it should if
> >> there is no data available but it never comes back. What am I doing
> >> wrong? I have searched through the sample code on apples developer site
> >> with no luck.
> >>
> >> NSPipe *vmPipe = [NSPipe pipe];
> >> NSFileHandle *vmRead = [vmPipe fileHandleForReading];
> >>
> >> [vm setLaunchPath: @"/usr/bin/vm_stat"]; // 1 page = 4096
> >> bytes
> >> [vm setStandardOutput: vmPipe];
> >> [vm launch];
> >> NSData *vmData = nil;
> >> int vmDataLength = 0;
> >> do {
> >> vmData = [vmRead availableData];
> >> vmDataLength = [vmData length];
> >> } while (vmDataLength != 0);
> >
> >
> > You can't do this. You need to run the runloop.
>
> For what? Neither NSPipe nor NSFileHandle rely on the runloop except for
> the InBackgroundAndNotify methods, as far as I'm aware. They are just
> thin wrappers around system calls.
Hmm. I thought we'd established a dependency on the runloop for even
basic uses of these classes. But it appears I'm mistaken.
>
> You need to run the runloop to get notified of an NSTask's termination,
> too, but he's not relying on that.
This is the only context in which I see NSPipe being used frequently, so
I probably just extended the runloop requirement to that case.
>
> Of course, he is potentially blocking his main thread, if this is run on
> the main thread, which is always bad. But the code should work.
Yeah, regardless of whether it's mandatory, it's almost certainly a good
idea. :)
--Kyle Sluder
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