C/C++: Capture stdout from a system() command


	FILE *results;
	int queen;
	if (!(results = popen("./precosat -f nqueens.cnf | tail -n +2 | head -n -1 | tr -d v | tr ' ' '\n' | grep -v '^$' | grep ^[0-9]", "r"))) {
		cout << "Unable to Execute Precosat" << endl << "./precosat -f nqueens.cnf | tail -n +2 | head -n -1 | tr -d v | tr ' ' '\n' | grep -v '^$' | grep ^[0-9]" << endl;
		exit(1);
	}
	for (i = 0; i < queens; i++) {
		fscanf(results,"%d",&queen);
		cout << "Queen #" << i+1 << " goes to [" << ((queen%queens)?(queen%queens):queens) << "]" << endl;
	}
	pclose(results);

Above, you will find an example that was used to extract data from the PrecoSAT SAT Solver in order to solve the N-Queens problem. It returns all positive variables, one per line.

You can see that after the call to popen, it creates a pointer to a file stream that can be used as a regular file to read the data from the called process.

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