String Validation in a Certain Format - c++

Question

I'm creating a simple chess game which uses shared memory. There are two players (Black,White) in the game and they are working in Strict Alternation principle. I get input from every player in turn-based sense and use them. My question is: I want the user to give the input like mov(a1,b2). After getting the input First: I want to validate if it is in the correct format and then I want to use the a1,b2 values in a function. Here is the part of my code:
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <iostream>
#include <string.h>
#include <sstream>
#include <algorithm>
#include <iterator>
#include <vector>
#include <stdlib.h>
#include <iostream>
using namespace std;
#define SHMSZ 27
int main() {
int shmid;
key_t key;
char *shm;
string cmd;
int check =1;
key = 111;
/*
* Locate the segment.
*/
if ((shmid = shmget(key, SHMSZ, 0666)) < 0) {
perror("shmget");
return 0;
}
/*
* Now we attach the segment to our data space.
*/
if ((shm = (char*) shmat(shmid, NULL, 0)) == (char *) -1) {
perror("shmat");
return 0;
}
cout << *shm << endl;
while(check)
{
if(*shm == '*') //checks if other player finished the game
{
cout<<"End of the game. Thank you for playing." <<endl;
*shm ='*';
exit(1);
}
while(*shm == 'B')
{
cout << "Enter a move" << endl;
cin >> cmd;
if(cmd=="eog") // Finish the game
{
cout<<"End of the game. Thank you for playing." <<endl;
*shm ='*';
exit(1);
}
*shm = 'W';
}
}
return 0;
}