Question

I am currently writing a program’s main function(the bare-bone function so far) so far I’ve only included the “end” command to end the program. Whenever anything else is typed that isn’t a command, it will output an error message. However, now that I’m inputting more commands within the loop, it doesn’t seem to be recognizing anything else. I’m writing a program that creates polynomials after prompting the user to enter coefficients and exponents.

The command is adc(add coefficient command) and after a space you’re supposed to add an integer standing for the coefficient and another space with another integer standing for the exponent.

Example: adc 4 5
Output: 4x^5

int main(void){
    char buf[5]; //Creates string array
    unsigned int choice;
    printf("Command? "); // Prompts user for command
    fflush(stdout);
    gets(buf); //Scans the input

    while(strncmp(buf, "end", 3) != 0) //Loop that goes through each case, so long as the command isn't "end".
    {
        switch( choice ){
        //Where the other cases will inevitably go
            if((strcmp(buf,"adc %d %d"))== 0){
            }
        break;
            default:
              printf("I'm sorry, but that's not a command.\n"); //Prints error message if input is not recognized command
    fflush(stdout);
              break;
        }
        printf("Command? "); //Recycles user prompt
        fflush(stdout);
        gets(buf);
    }
    puts("End of Program."); //Message displayed when program ends
}

Answer 1

You can’t use a format string like this: strcmp(buf,"adc %d %d") to test for a certain kind of input. Your strcmp will only signal string equality if the use inputs literally: "adc %d %d", not adc followed by two integers.

You’ll need to parse the input string manually, by tokenizing around whitespace characters, checking the first token with strcmp against e.g. adc, then parsing the numbers separately.

I don’t notice any case statements in your switch. It looks like you can just remove the switch, since you’re not using choice anywhere.

Also, don’t use gets, use fgets instead.