Write the program expr, which evaluates a reverse Polish expression from the command line, where each operator or operand is a separate argument.For e.g expr 2 3 4 + * evaluates 2 *(3 + 4)

#include <stdio.h>
#include <math.h>   /* atof()   */

#define   MAXOP   100   /* max size of operand or operator */
#define   NUMBER   '0'   /*signal that a number was found */

int getop(char []);
void ungets(char []);
void push(double);
double pop(void);

/* reverse Polish calculator; uses command line */
int main(){
    char s[MAXOP];
    double op2;

    while(--argc > 0){
       ungets(" ");     /*push end of argument */
       ungets(*++argv);   /* push an argument */
       switch(getop(s)){
       case NUMBER:
             push(atof(s));
             break;
       case '+':
            push(pop() + pop());
            break;
       case '*':
            push(pop() * pop());
            break;
       case '-':
            op2 = pop();
            push(pop() - op2);
            break;
       case '\':
           op2 = pop();
           if (op2 != 0.0)
               push(pop() / op2);
           else
              printf("error : zero divisor\n");
           break;
      default:
          printf("error: unknown command %s\n", s);
          argc = 1;
          break;
                
       }
    }
     printf("\t %.8g\n",, pop());
     return 0;
}