./a.out test.txt

matriz.cpp

#include <iterator>
#include <sstream>
#include <iostream>
#include <fstream>
#include <cctype>
#include <algorithm>

int * size_of_matrix(std::istream& str) {
	static int size[2];
	int rows = 0;
	int words = 0;
	std::string row;
	bool word(false);
	std::for_each(std::istreambuf_iterator<char>(str),
		std::istreambuf_iterator<char>(),
		[&](unsigned char c) {
		word = !std::isspace(c)
			&& (word || ++words);
		c == '\n' && ++rows; });
	size[0] = rows; //filas
	size[1] = words/rows; //columnas
	return size;
}

int main(int argc, char* argv[])
{
	std::string input_text;
	std::ifstream inFile(argv[1]);
	int * size = size_of_matrix(inFile);
	std::cout << "Number of rows: " << size[0] << std::endl;
	std::cout << "Number of columns: " << size[1] << std::endl;
	std::getline(std::cin, input_text);
	return 0;
}

test.txt

1   2	3
4  5	6
7 8 9
10  11 		12