How to take command-line input and verify that it is an int?

[crabpot8]

Hi all,

I have a small part of my program that I would like to revise. The problem is that if someone enters text, it just gets converted to 1 as an int. I would like to print an error message and ask them for an int again.

Thanks in advance,
crab

{    
     int in;
     cout << endl << "Please input an integer: ";
     cin >> in;
 
     cout << "The int entered was : " << in; 
}

[boxfish]

If you cin to a variable of type int, and the user does not enter an integer, cin's fail flag will be raised, and your program will not accept any more input after that. The cin.fail() function returns true if the fail flag is raised, and the cin.clear() function lowers it again. After the line of code that prompts the user for input, check whether the fail flag is raised with the cin.fail() function, and if it is, lower it with the cin.clear() function and ask the user for input again. It would probably be best to put all this into a do {...} while (...); loop:

do {
    Reset the fail flag
    Ask the user for input
} while (The input is still not a number);
 

Hope this helps.

[weaknessforcats]

Also, don't forget to eat the data that caused the error in the first place. Clearing the failbit will not remove the cause of the error. That is, if text cause the error then the text has to be removed in addition to clearing the failbit.