Re: [C400-L] Validating Numeric values

[James Rich <james@xxxxxxxxxxx>]

On Thu, 7 Oct 2004, Chris Wolcott wrote:

> C is not my 'native' language, so I'm asking what the most efficient way
> to validate a string as containing a numeric value is.  The ato?() and
> sscanf() functions just stop when they encounter a non-numeric, but do
> not tell you that they did.
>
> I need to verify that a string contains a valid numeric value.  (I.E. "
> +100" not "1 + 00" nor even "1+00  ", let alone "BOB   ")  (ato?() &
> sscanf() would return NULL or 1 in each case.)

It sounds like strtol() is what you are looking for.  From the man page:

       The  remainder  of  the  string is converted to a long int
       value in the obvious manner, stopping at the first charac-
       ter  which  is  not  a valid digit in the given base.  (In
       bases above 10, the letter `A' in either  upper  or  lower
       case  represents 10, `B' represents 11, and so forth, with
       `Z' representing 35.)

James Rich

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