[kman42]

I have a log file that I want to access. The problem is that the name changes every so often. The root of the name is always the same and it is always in the same directory. What's the best way to deal with this?

For instance, the file might be
~/Library/myApp/log01.txt

Or
~/Library/myApp/log02.txt

Basically, the log file gets replaced periodically with the next increment. There is never more than one log file.

I want to get the contents of the file using a URL, like this:

Code:
NSString *logContents=[NSString stringWithContentsOfURL:logURL];

My problem is that I don't know how to generate the logURL with a constantly changing file name.

thanks,
kman

[Rickster]

Use -[NSFileManager directoryContentsAtPath:] to list all files in the directory containing your log file, look for names that match the LogXX.txt pattern, and take the one with the highest number.

You could also use -[NSFileManager fileExistsAtPath:] in a loop, starting with either Log01 or the highest-numbered file you find last time, and incrementing the number until you find the current log. But that has a good chance of taking forever to find what you're after.

[kman42]

Here's what I've tried so far:

Code:
-(IBAction)openLogFile:(id)sender {

    NSOpenPanel *oPanel = [NSOpenPanel openPanel];
    NSString *result;
    [oPanel setAllowsMultipleSelection:NO];
    result = [oPanel runModalForDirectory:NSHomeDirectory()
                                     file:nil types:nil];
    logFile = [[oPanel filenames] objectAtIndex:0];
   
    NSScanner *pathScanner = [NSScanner scannerWithString:logFile];
    [pathScanner scanUpToString:@"/log" intoString:&logFileDirectory];
    NSLog(@"logFileDirectory=%@",logFileDirectory);
        
}
    
-(void)getInfoFromLog {
    NSAutoreleasePool *logpool = [[NSAutoreleasePool alloc] init];

    NSArray *directoryContents=[NSFileManager directoryContentsAtPath:logFileDirectory];

    NSString *currentLogFile;
    NSEnumerator *enumerator = [directoryContents objectEnumerator];
    id file;

    while (file = [enumerator nextObject]) {
        NSScanner *fileNameScanner = [NSScanner scannerWithString:file];
       if ([fileNameScanner scanUpToString:@"log" intoString:NULL]) {
            currentLogFile=file;
        }
  }

...

I get a selector unknown error in [NSFileManager directoryContentsAtPath:logFileDirectory]

Any help would be great! And if you participate in Folding@Home, you can download this little helper app here . Aside from this issue, it works pretty well. You are welcome to modify the app in any way you see fit.

kman

[Rickster]

It's probably better to use NSString's path utilities to get the parent directory of the chosen file. Replace the last three lines of -openLogFile: with:

Code:
logFileDirectory = [logFile stringByDeletingLastPathComponent];

The error you're getting is because -directoryContentsAtPath: is an instance method on NSFileManager, not a class method. You'll want to use the class method +defaultManager to get an instance you can manipulate. With that change, and eliminating further unnecessary use of NSScanner:

Code:
-(void)getInfoFromLog {
    NSAutoreleasePool *logpool = [[NSAutoreleasePool alloc] init];

    NSArray *directoryContents = [[NSFileManager defaultManager] directoryContentsAtPath:logFileDirectory];

    NSString *currentLogFile;
    NSEnumerator *enumerator = [directoryContents objectEnumerator];
    id file;

    while ((file = [enumerator nextObject])) {
       if ([file rangeOfString:@"log" options:NSCaseInsensitiveSearch].location != NSNotFound)
            currentLogFile = file;
    }

    ...

BTW, unless your log-processing code involves the creation of a whole lot of autoreleased objects, you don't really need the local autorelease pool. You might want to test performance with and without -- it's said that premature optimization is the root of all evil.

[kman42]

Originally posted by Rickster:
It's probably better to use NSString's path utilities to get the parent directory of the chosen file. Replace the last three lines of -openLogFile: with:

Code:
logFileDirectory = [logFile stringByDeletingLastPathComponent];

The error you're getting is because -directoryContentsAtPath: is an instance method on NSFileManager, not a class method. You'll want to use the class method +defaultManager to get an instance you can manipulate. With that change, and eliminating further unnecessary use of NSScanner:

Code:
-(void)getInfoFromLog {
    NSAutoreleasePool *logpool = [[NSAutoreleasePool alloc] init];

    NSArray *directoryContents = [[NSFileManager defaultManager] directoryContentsAtPath:logFileDirectory];

    NSString *currentLogFile;
    NSEnumerator *enumerator = [directoryContents objectEnumerator];
    id file;

    while ((file = [enumerator nextObject])) {
       if ([file rangeOfString:@"log" options:NSCaseInsensitiveSearch].location != NSNotFound)
            currentLogFile = file;
    }

    ...

BTW, unless your log-processing code involves the creation of a whole lot of autoreleased objects, you don't really need the local autorelease pool. You might want to test performance with and without -- it's said that premature optimization is the root of all evil.

Thanks! That helps tremendously. I had no idea there was an NSString method for deleting the last path component. That has been the bane of learning Cocoa. There are all of these great classes and methods that one may never know about. I never would have thought to look in NSString for a method to deleted a portion of a path!

Also, the autorelease pool is there because that same method actually goes on to retrieve the info off of the web.

kman

[kman42]

One last question. What's the '.location' in the rangeOfString line?

thanks,
kman

[Rickster]

-rangeOfString: returns an NSRange, which is a struct. ".location" gets an element of that struct.

Yeah, there are many things in Cocoa -- especially in Foundation -- that aren't in places you'd first think to look for them. (It all makes sense eventually though.) The best way to learn is just to explore, I think.