How to check if a string is a number?

Question

I want to check if a string is a number with this code. I must check that all the chars in the string are integer, but the while returns always isDigit = 1. I don\'t know wh

Answer 1

#include 
#include 
char isNumber(char *text)
{
    int j;
    j = strlen(text);
    while(j--)
    {
        if(text[j] > 47 && text[j] < 58)
            continue;

        return 0;
    }
    return 1;
}
int main(){
    char tmp[16];
    scanf("%s", tmp);

    if(isNumber(tmp))
        return printf("is a number\n");

    return printf("is not a number\n");
}

You can also check its stringfied value, which could also work with non Ascii

char isNumber(char *text)
{
    int j;
    j = strlen(text);
    while(j--)
    {
        if(text[j] >= '0' && text[j] <= '9')
            continue;

        return 0;
    }
    return 1;
}