Thread: using isdigit()

Hello,

I can't seem to correctly use isdigit(). I have a variable that is assigned the value of argv[1], a value from the command-line. I want to check to see if that value is an integer or not. Here is what I have:

Code:

#include <ctype.h>

[...]
if(isdigit(myVar) == 0) {
        printf("myVar is not a digit.");
} else {
        printf("myVar is a digit.");
}

But not matter the value of myVar, be it "12" or "abcd", it keeps returning 0 for isdigit(). Any help? Like I said above, basically I am just trying to figure out if the value of argv[1] is a number or not.

Thanks!

isdigit() checks characters, not strings.

When I run it with myVar = "b" and myVar = 5 the output is the same - a zero.

Is there a way to check a string (like argv[1]) and see if it contains just numbers?

Code:

#include <stdio.h>
#include <ctype.h>

int main()
{
    char myVar = 'a';

    if(isdigit(myVar) == 0) {
         printf("myVar is not a digit.");
    } else {
         printf("myVar is a digit.");
    }

    return 0;
}