The basics of detecting a file change event without excess libraries. Very inefficient.

file_change_event.h

#include	<cstring>
#define		_missingFile	0x601DE0
using namespace std;
class fileListener
{
	private:
		struct stat st;

	public:
	class file_
	{
		public:
		string name;
		unsigned long long modify;
		unsigned int mode;
	};
	file_ file;

	int addListener(string s) {    
		file.name = s;
		stat( file.name.c_str(), &st );
		file.modify = st.st_mtime;
		file.mode	= st.st_mode;
		return ( file.mode != _missingFile )? 1 : 0;
	}

	int listenModify(void) {
		while(1)
		{
			stat( file.name.c_str(), &st );
			file.mode	= st.st_mode;
			if( file.mode == _missingFile ) return 0;
			if( file.modify != st.st_mtime )
			{
				file.modify = st.st_mtime;
				return 1;
			}
		}
		return 0;
	}

};

fileListener fl.addListender("filename.txt");
while(fl.listenModify) { cout << "file changed!"; }