Methods of Reloading Config Files

Example1.m

FileSystemWatch* watcher = [[FileSystemWatch alloc] init];
[watcher watchFileAtPath:@"path/to/config.plist" target:self action:@selector(fileChanged:)];

...

- (void)fileChanged:(FileSystemWatch*)watcher
{
    NSLog(@"File changed, time to reload");
}

Example2.m

[watcher stopWatching];
[watcher release];

FileSystemWatch.h

#import <Foundation/Foundation.h>

@interface FileSystemWatch : NSObject

- (void)watchFileAtPath:(NSString*)path target:(id)target action:(SEL)action;
- (void)stopWatching;

@end

FileSystemWatch.m

#import "FileSystemWatch.h"

#include <sys/event.h>
#include <sys/time.h> 
#include <fcntl.h>


@interface FileSystemWatch ()
@property (nonatomic,retain) NSString* path;
@property (nonatomic,assign) id target;
@property (nonatomic,assign) SEL action;
@property (nonatomic,assign) int fildes;
@property (nonatomic,assign) int kq;
@property (nonatomic,retain) NSThread* watchThread;

@end

@implementation FileSystemWatch
@synthesize path = _path;
@synthesize target = _target;
@synthesize action = _action;
@synthesize fildes = _fildes;
@synthesize kq = _kq;
@synthesize watchThread = _watchThread;

- (void)dealloc
{
	[_path release], _path = nil;
	[_watchThread release], _watchThread = nil;
	[super dealloc];
}

- (void)watchFileAtPath:(NSString*)path target:(id)target action:(SEL)action
{
	self.path = path;
	self.target = target;
	self.action = action;

	self.fildes = open([self.path UTF8String], O_RDONLY);
	if(self.fildes <= 0)
	{
		return;
	}
	self.kq = kqueue();

	self.watchThread = [[[NSThread alloc] initWithTarget:self selector:@selector(watchInBackground) object:nil] autorelease];
	[self.watchThread start];
}

- (void)stopWatching
{
	close(self.kq);
	close(self.fildes);
	[self.watchThread cancel];
}

- (void)watchInBackground
{
	int status;
	struct kevent change;
	struct kevent event;

	EV_SET(&change, self.fildes, EVFILT_VNODE,
		   EV_ADD | EV_ENABLE | EV_ONESHOT,
		   NOTE_DELETE | NOTE_EXTEND | NOTE_WRITE | NOTE_ATTRIB,
		   0, 0);

	while(status > 0)
	{
		status = kevent(self.kq, &change, 1, &event, 1, NULL);
		
		if(status > 0)
		{
			if([self.target respondsToSelector:self.action])
				[self.target performSelectorOnMainThread:self.action withObject:self waitUntilDone:YES];
		}
	}

	close(self.kq);
	close(self.fildes);
}

@end

kQueueTest.c

#include <sys/event.h>
#include <sys/time.h> 
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h> 

int main(int argc,char** argv)
{
	int fildes;
	int kq;
	int status;
	struct kevent change;
	struct kevent event;

	kq = kqueue();
	fildes = open("test.plist", O_RDONLY);
	if(fildes <= 0)
	{
		printf("No such file...\n");
		return -1;
	}

	EV_SET(&change, fildes, EVFILT_VNODE,
					EV_ADD | EV_ENABLE | EV_ONESHOT,
					NOTE_DELETE | NOTE_EXTEND | NOTE_WRITE | NOTE_ATTRIB,
					0, 0);

	for(;;)
	{
		status = kevent(kq, &change, 1, &event, 1, NULL);

		if(status > 0) 
		{
			printf("Reload config file\n");
		}
	}

	close(kq);
	close(fildes);
	return 0;
}

StatTest.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(int argc,char** argv)
{
	struct stat buffer;
	int status;
	int fildes = open("test.plist",O_RDONLY);
	time_t startTime = 0;
	if(fildes <= 0)
	{
		printf("No such file...\n");
		return -1;
	}
	
	for(;;)
	{
		status = fstat(fildes,&buffer);
		if(startTime != buffer.st_atime)
		{
			startTime = buffer.st_atime;
			printf("Reload Config File\n");
		}
		usleep(100*1000); //Sleep for 0.1 seconds
	}
	
	close(fildes);
	return 0;
}