C equivalent of Java's isnumeric

zaichik · 02-08-2005, 07:12 PM

Hi all,

I am wondering if C has an equivalent of Java's isNumeric method. I want users to be able to enter a range of IP addresses, like 10.1.1.5-15. I use sscanf( ip, "%d.%d.%d.%d", octet1, octet2, octet3, octet4 ) at the present to parse the octets into separate ints. However, I would like to allow the users to enter a range, and would use something like:

Code:

sscanf( ip, "%d.%d.%d.%s", octet1, octet2, octet3, strOctet4 );
if( isnumeric( strOctet4 )) {
    sscanf( strOctet4, "%d", octet4 );
}
else {
    /* use something like strtok() to break
        strOctet4 into two ints representing a
        lower and upper range.
     */
}

If there is no C function similar to isNumeric, what would you recommend? Checking the ASCII value of each char in strOctet4 to see if it falls in the range of a number?

Once again, thanks in advance!

jtshaw · 02-08-2005, 07:19 PM

ctype.h has the following functions:

int isalnum(int c);
int isalpha(int c);
int isascii(int c);
int isblank(int c);
int iscntrl(int c);
int isdigit(int c);
int isgraph(int c);
int islower(int c);
int isprint(int c);
int ispunct(int c);
int isspace(int c);
int isupper(int c);
int isxdigit(int c);

itsme86 · 02-08-2005, 07:36 PM

Like jtshaw pointed out, ctype.h is where you're going to want to look. You can write you own isnumeric() like this:

Code:

int isnumeric(char *str)
{
  while(*str)
  {
    if(!isdigit(*str))
      return 0;
    str++;
  }

  return 1;
}

zaichik · 02-08-2005, 08:06 PM

Brilliant--thanks, guys!