windows下c语言获取程序当前的执行目录，读文件的代码片

#include "stdafx.h"
#include "stdlib.h"
#include <direct.h>
#include <string.h>

int _tmain(int argc, char* argv[])
{
	char* buffer;

	// Get the current working directory: 
	if( (buffer = _getcwd( NULL, 0 )) == NULL )
		perror( "_getcwd error" );
	else
	{
		printf( "%s \nLength: %d\n", buffer, strnlen(buffer,1024) );
		free(buffer);
	}

	FILE *fp = fopen("input_left.ppm", "rb");
	if (!fp) 
	{
		printf("exit");
		return NULL;
	}
	else
	{
		printf("get");
	}

	getchar();


	return 0;
}