cryptography-utils/shift.cc

#include <iostream>
#include <cctype>

int main(int argc, char** argv)
{
	char* text;
	int key;
	if(argc < 3)
	{
		std::cout << "Usage: " << argv[0] << " <plain text> <key>" << std::endl;
		return 0;
	}
	text = argv[1];
	key = atoi(argv[2]);
	
	for(int i = 0; text[i] != 0; ++i)
	{
		if(text[i] == ' ')
		{
			std::cout << ' ';
			continue;
		}
		char c = std::tolower(text[i])+key;
		if(c < 'a') c+=26;
		if(c > 'z') c-=26;
		std::cout << c;
	}
	std::cout << std::endl;
	return 0;
}