Reading input commands with up to 3 commands - c++

Question

I have a program which prompts the user to input a command. Based on the command, it will perform different functions.
example commands:
help
set value 20
set another 30
print this
print that
How can I split these into 3 separate variables and continue the program? I'm having trouble with a simple
string command;
string item;
string value;
cin >> command >> item >> value;
Because unless the user inputs all three, the program won't continue.
This is what I came up with, I can't answer my own question so this will do.
Thank you for the input. This is what I came up with after researching some of those functions mentioned by #JoachimPileborg. It seems to work just how I need it.
int main() {
bool done = false;
char input[30];
std::string command, item, value;
//output instructions, get user input
std::cout << "Type 'help' to find more about commands.\n";
do{
std::cin.getline(input,30);
//parse user input from char to an array
istringstream iss;
string commands[3];
iss.str (input);
for (int i = 0; i < 3; i++) {
iss >> commands[i];
}
//set each part of the array to appropriate value
command = commands[0];
item = commands[1];
value = commands[2];
//properly sort out which command is being called
//first: check if command has 3 parts
if (commands[2].length() != 0){
cout << command << item << value;
}
//second:if it doesnt have 3 parts, check if it has 2 parts
else if (commands[1].length() != 0){
cout << command << item;
}
//third:if it doesn't have 2 parts, check for 1 part
else if (commands[0].length() != 0){
if (command == "help"){
commandline.help();
done = true;
}
else{
cout << "Incorrect Command! Please try again!";
}
}
else
cout << "No command found, please try again!";
}while(!done);
}

Answer 1

"How can I split these into 3 separate variables and continue the program?"
Don't have distinct variables, use an appropriate standard library container to collect a variable number of parameters given for a command.
The very simplest way,- I can imagine -, how to implement such thing, would probably look like this:
std::string cmdline;
while(cmdline != "quit") {
std::cout << "Enter command > ";
std::getline(std::cin),cmdline);
if(!cmdline.empty()) {
std::istringstream iss(cmdline);
std::vector<std::string> cmditems;
std::string cmditem;
while(iss >> cmditem) {
cmditems.push_back(cmditem);
}
if(cmditems.empty()) { // Just whitespaces input
continue;
}
// accessing cmditems[0] is always safe at this point
if(cmditems[0] == "help") {
printHelp();
}
else if(cmditems[0] == "set") {
// Check if the number of command arguments actually
// fit the required ones
if(cmditems.size() < 3) {
std::cerr << "Please enter a name and value!" << std::endl;
continue;
}
setValue(cmditems[1],cmditems[2]);
}
else if(cmditems[0] == "print") {
// Check if the number of command arguments actually
// fit the required ones
if(cmditems.size() < 2) {
std::cerr << "Please enter a name to print!" << std::endl;
continue;
}
printValue(cmditems[1]);
}
// and so on ...
}
}