[Baypiggies] quick question: regex to stop naughty control characters
Dennis Reinhardt
DennisR at dair.com
Wed Apr 25 22:02:55 CEST 2007
At 12:44 PM 4/25/2007, Shannon -jj Behrens wrote:
>using FormEncode with a regex that looks like r".{1,128}$".
First we have to re-write this. This regex matches on any string having
between 1 and 128 characters immediately preceding the end of string. So,
a string 10 characters long would match because a length 10 string has 1
character preceding end. A string 1000 characters long would match as well.
A regex of r"^.{1,128}$" would match only when there are between 1 and 128
characters and no more or no less between start and end.
Now, we can define exceptions which prevent matching. A regex of
r"^[^\r\n]{1,128}$" will match the same size strings but fail if either an
embedded CR or LF is included. The extension to other control characters
is easy.
Yeah, I know I used "^" twice to mean two different things (start of string
and not, respectively). That is just regex language, not a mistake on my part.
Regards, Dennis
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| Dennis | DennisR at dair.com |
| Reinhardt | http://www.dair.com |
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