Way to deal with multiple user arguments in C++? - c++

Question

Task Commands Picture Ok, I've progressed a bit more from my previous work but I just can't get past this issue which probably isn't that big. My task, which is basically a text file editor, requires multiple user arguments after the program begins running, ranging from let's say 1 such as "details" to 3 or 4 with random user input like display x y or savepart x y (see attached image). My code currently takes in the first line the user inputs using cin and getline but it can only read known strings such as load userinput.txt (which is the filename), and quit and I don't know how I can store the user's entered values for variables. How do I solve this?
What basically needs to probably change is the getline under the while loop or what's written in the if statements but I've tried everything.
#include <iostream>
#include <fstream>
#include <string>
#include <stdio.h>
using namespace std;
string secondword;
string fword;
string line;
ifstream myfile;
fstream fFile;
bool running = true;
int x;
int length;
int main(int argc, char* argv[]) {
while (running) {
getline(cin, fword); //Reads first line user inputs
//if first word equals laod command load file to memory
if (fword == "load userinput.txt") {
ifstream myfile("userinput.txt", ifstream::binary);
myfile.seekg(0, myfile.end); //Searches till end of file
length = myfile.tellg(); //Sets length as total number of chars in file
myfile.seekg(0, myfile.beg); //Searches from the beginning
char* buffer = new char[length]; //Allocates file memory to pointer
cout << "Reading " << length << " characters... " << endl;
myfile.read(buffer,length); //reads file and compares buffer size with legnth size
if (myfile)
cout << "All characters read and stored in memory sucessfully" << endl;
else
cout << "error: only " << myfile.gcount() << " can be read" << endl;;
myfile.close();
}
//Quit
if (fword == "quit") {
running = false; //Breaks while loop statement
cout << "User has quit the program" << endl;
}
//Clear all lines in text
if (fword == "clear all") {
fFile.open("userinput.txt", ios::out | ios::trunc);
fFile.close();
cout << "All lines have been cleared" << endl;
}
//Display All Text
if (fword == "display text") {
myfile.open("userinput.txt", ios::in);
while (getline(myfile, line)) { //read data from file object and put it into string.
cout << line << endl; //print the data of the string
}
}
}
return 0;
}