Hi Folks, I've got the following url route and i'm wanting to make sure that a segment of the route will only accept numbers. as such, i can provide some regex which checks the word.
/page/{currentPage}
so.. can someone give me a regex which matches when the word is a number (any int) greater than 0 (ie. 1 <-> int.max).
cheers!
If you want it greater than 0, use this regex:
/([1-9][0-9]*)/
This'll work as long as the number doesn't have leading zeros (like '03').
However, I recommend just using a simple [0-9]+ regex, and validating the number in your actual site code.
string testString = @"/page/100";
string pageNumber = Regex.Match(testString, "/page/([1-9][0-9]*)").Groups[1].Value;
If not matched pageNumber will be ""
i'm not after any code, like perl, c#, etc.
this is the text that will go into any RegEx expression.
i also do not need to check for the word 'page' or the '/' character, etc.
i just wanted to make sure the string/variable 'currentPage' is only a number, using regex.
how do these two differ, please?
#[1-9]+# vs /([1-9][0-9]*)/
/^[1-9][0-9]*$/
Problems with other answers:
/([1-9][0-9]*)/ // Will match -1 and foo1bar
#[1-9]+# // Will not match 10, same problems as the first
[1-9] // Will only match one digit, same problems as first
While Jeremy's regex isn't perfect (should be tested in context, against leading characters and such), his advice is good: go for a generic, simple regex (eg. if you must use it in Apache's mod_rewrite) but by any means, handle the final redirect in server's code (if you can) and do a real check of parameter's validity there.
Otherwise, I would improve Jeremy's expression with bounds: /\b([1-9][0-9]*)$/
Of course, a regex cannot provide a check against any max int, at best you can control the number of digits: /\b([1-9][0-9]{0,2})$/ for example.
This will match any string such that, if it contains /page/, it must be followed by a number, not consisting of only zeros.
^(?!.*?/page/([0-9]*[^0-9/]|0*/))
(?! ) is a negative look-ahead. It will match an empty string, only if it's contained pattern does not match from the current position.
This one would address your specific problem. This expression
/\/page\/(0*[1-9][0-9]*)/ or "Perl-compatible" /\/page\/(0*[1-9]\d*)/
should capture any non-zero number, even 0-filled. And because it doesn't even look for a sign, - after the slash will not fit the pattern.
The problem that I have with eyelidlessness' expression is that, likely you do not already have the number isolated so that ^ and $ would work. You're going to have to do some work to isolate it. But a general solution would not be to assume that the number is all that a string contains, as below.
/(^|[^0-9-])(0*[1-9][0-9]*)([^0-9]|$)/
And the two tail-end groups, you could replace with word boundary marks (\b), if the RE language had those. Failing that you would put them into non-capturing groups, if the language had them, or even lookarounds if it had those--but it would more likely have word boundaries before lookarounds.
Full Perl-compatible version:
/(?<![\d-])(0*[1-9]\d*)\b/
I chose a negative lookbehind instead of a word boundary, because '-' is not a word-character, and so -1 will have a "word boundary" between the '-' and the '1'. And a negative lookbehind will match the beginning of the string--there just can't be a digit character or '-' in front.
You could say that the zero-width assumption ^ is just one of the cases that satisfies the zero-width assumption (?<![\d-]).