I'm using NSTask to run a background process, monitor its output, and
ultimately present a message to the user. All has been fine with this 10.2
through 10.6, as far as I know. Now under 10.7 I saw a case where my code did
not receive quite all the stdout output from the background process. I saw this
once; I haven't tried running it a huge number of times, but it is definitely
not the common case. (And I've never seen it in dev mode running under the
debugger, only on a machine without dev tools. Also BTW, the output of the bg
process is plain ASCII, no worries about multi-byte sequences.) Does anybody
see anything wrong with this code (severely stripped for legibility):
- (void) doSomeTask: (NSTask *) task
{
NSTask * task = [[NSTask alloc] init];
[task setLaunchPath: cmdpath];
[task setArguments: [self getArgs]];
[task setStandardError: [NSPipe pipe]];
[task setStandardOutput: [NSPipe pipe]];
[task launch];
curScanTask = [task retain];
curStdOutStr = [[NSMutableString alloc] init];
curStdErrStr = [[NSMutableString alloc] init];
curStdOut = [[task standardOutput] fileHandleForReading];
curStdErr = [[task standardError] fileHandleForReading];
[[NSNotificationCenter defaultCenter]
addObserver: self selector: @selector( processStdOut: )
name: NSFileHandleReadCompletionNotification
object: curStdOut];
[[NSNotificationCenter defaultCenter]
addObserver: self selector: @selector( processStdErr: )
name: NSFileHandleReadCompletionNotification
object: curStdErr];
[curStdOut readInBackgroundAndNotify];
[curStdErr readInBackgroundAndNotify];
}
- (void) processStdOut: (NSNotification *) ntc
{
NSFileHandle *f = [ntc object];
NSData *d = [[ntc userInfo] objectForKey:
NSFileHandleNotificationDataItem];
if( [d length] == 0 )
[self processPipeClose];
else
{
[f readInBackgroundAndNotify];
[curStdOutStr appendString:
[[[NSString alloc] initWithData: d encoding:
NSASCIIStringEncoding] autorelease]];
}
}
- (void) processStdErr: (NSNotification *) ntc
{
NSFileHandle *f = [ntc object];
NSData *d = [[ntc userInfo] objectForKey:
NSFileHandleNotificationDataItem];
if( [d length] == 0 )
[self processPipeClose];
else
{
[f readInBackgroundAndNotify];
[curStdErrStr appendString:
[[[NSString alloc] initWithData: d encoding:
NSASCIIStringEncoding] autorelease]];
}
}
- (void) processPipeClose
{
[curStdOutStr appendString:
[[[NSString alloc] initWithData: [curStdOut
readDataToEndOfFile] encoding: NSASCIIStringEncoding] autorelease]];
[[NSNotificationCenter defaultCenter]
removeObserver: self
name: NSFileHandleReadCompletionNotification
object: curStdOut];
curStdOut = nil;
[curStdErrStr appendString:
[[[NSString alloc] initWithData: [curStdErr
readDataToEndOfFile] encoding: NSASCIIStringEncoding] autorelease]];
[[NSNotificationCenter defaultCenter]
removeObserver: self
name: NSFileHandleReadCompletionNotification
object: curStdErr];
curStdErr = nil;
}
--
Scott Ribe
scott_r...@elevated-dev.com
http://www.elevated-dev.com/
(303) 722-0567 voice
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