I'm using Scrapy to scrape a web site. I'm stuck at defining properly the rule for extracting links.
Specifically, I need help to write a regular expression that allows urls like:
https://discuss.dwolla.com/t/the-dwolla-reflector-is-now-open-source/1352
https://discuss.dwolla.com/t/enhancement-dwolla-php-updated-to-2-1-3/1180
https://discuss.dwolla.com/t/updated-java-android-helper-library-for-dwollas-api/108
while forbidding urls like this one
https://discuss.dwolla.com/t/the-dwolla-reflector-is-now-open-source/1352/12
In other words, I want urls that end with digits (i.e., /1352 in the example abpve), unless after these digits there is anything after (i.e., /12 in the example above)
I am by no means an expert of regular expressions, and I could only come up with something like \/(\d+)$, or even this one ^https:\/\/discuss.dwolla.com\/t\/\S*\/(\d+)$, but both fail at excluding the unwanted urls since they all capture the last digits in the address.
--- UPDATE ---
Sorry for not being clear in the first place. This addition is to clarify that the digits at the of URLS can change, so the /1352 is not fixed. As such, another example of urls to be accepted is also:
https://discuss.dwolla.com/t/updated-java-android-helper-library-for-dwollas-api/108
This is probably the simplest way:
[^\/\d][^\/]*\/\d+$
or to restrict to a particular domain:
^https?:\/\/discuss.dwolla.com\/.*[^\/\d][^\/]*\/\d+$
See live demo.
This regex requires the last part to be all digits, and the 2nd last part to have at least 1 non-digit.
Here is a java regex may fit your requirements in java style. You can specify number of digits N you are excepting in {N}
^https://discuss.dwolla.com/t/[\\w|-]+/[\\d]+$
Related
I have this regex (not mine, taken from here)
^[^\.]+\.example\.org$
The regex will match *.example.org (e.g. sub.example.org), but will leaves out sub-subdomain (e.g. sub.sub.example.org), that's great and it is what I want.
But I have other requirement, I want to match subdomain that contain specific string, in this case press. So the regex will match following (literally any subdomain that has word press in it).
free-press.example.org
press.example.org
press23.example.org
I have trouble finding the right syntax, have looked on the internet and mostly they works only for standalone text and not domain like this.
Ok, let's break down what the "subdomain" part of your regex does:
[^\.]+ means "any character except for ., at least once".
You can break your "desired subdomain" up into three parts: "the part before press", "press itself", and "the part after press".
For the parts before and after press, the pattern is basically the same as before, except that you want to change the + (one or more) to a * (zero or more), because there might not be anything before or after press.
So your subdomain pattern will look like [^\.]*press[^\.]*.
Putting it all together, we have ^[^\.]*press[^\.]*\.example\.org$. If we put that into Regex101 we see that it works for your examples.
Note that this isn't a very strict check for valid domains. It might be worth thinking about whether regexes are actually the best tool for the "subdomain checking" part of this task. You might instead want to do something like this:
Use a generic, more thorough, domain-validation regex to check that the domain name is valid.
Split the domain name into parts using String.split('.').
Check that the number of parts is correct (i.e. 3), and that the parts meet your requirements (i.e. the first contains the substring press, the second is example, and the third is org).
If you're looking for a regex that matches URLs whose subdomains contain the word press then use
^[^\.]*press[^\.]*\.example\.org$
See the demo
I'm using CodeIgniter to write an app where a user will be allowed to register an account and is assigned a URL (URL slug) of their choosing (ex. domain.com/user-name). CodeIgniter has a URL routing feature that allows the utilization of regular expressions (link).
User's are only allowed to register URL's that contain alphanumeric characters, dashes (-), and under scores (_). This is the regex I'm using to verify the validity of the URL slug: ^[A-Za-z0-9][A-Za-z0-9_-]{2,254}$
I am using the url routing feature to route a few url's to features on my site (ex. /home -> /pages/index, /activity -> /user/activity) so those particular URL's obviously cannot be registered by a user.
I'm largely inexperienced with regular expressions but have attempted to write an expression that would match any URL slugs with alphanumerics/dash/underscore except if they are any of the following:
default_controller
404_override
home
activity
Here is the code I'm using to try to match the words with that specific criteria:
$route['(?!default_controller|404_override|home|activity)[A-Za-z0-9][A-Za-z0-9_-]{2,254}'] = 'view/slug/$1';
but it isn't routing properly. Can someone help? (side question: is it necessary to have ^ or $ in the regex when trying to match with URL's?)
Alright, let's pick this apart.
Ignore CodeIgniter's reserved routes.
The default_controller and 404_override portions of your route are unnecessary. Routes are compared to the requested URI to see if there's a match. It is highly unlikely that those two items will ever be in your URI, since they are special reserved routes for CodeIgniter. So let's forget about them.
$route['(?!home|activity)[A-Za-z0-9][A-Za-z0-9_-]{2,254}'] = 'view/slug/$1';
Capture everything!
With regular expressions, a group is created using parentheses (). This group can then be retrieved with a back reference - in our case, the $1, $2, etc. located in the second part of the route. You only had a group around the first set of items you were trying to exclude, so it would not properly capture the entire wild card. You found this out yourself already, and added a group around the entire item (good!).
$route['((?!home|activity)[A-Za-z0-9][A-Za-z0-9_-]{2,254})'] = 'view/slug/$1';
Look-ahead?!
On that subject, the first group around home|activity is not actually a traditional group, due to the use of ?! at the beginning. This is called a negative look-ahead, and it's a complicated regular expression feature. And it's being used incorrectly:
Negative lookahead is indispensable if you want to match something not followed by something else.
There's a LOT more I could go into with this, but basically we don't really want or need it in the first place, so I'll let you explore if you'd like.
In order to make your life easier, I'd suggest separating the home, activity, and other existing controllers in the routes. CodeIgniter will look through the list of routes from top to bottom, and once something matches, it stops checking. So if you specify your existing controllers before the wild card, they will match, and your wild card regular expression can be greatly simplified.
$route['home'] = 'pages';
$route['activity'] = 'user/activity';
$route['([A-Za-z0-9][A-Za-z0-9_-]{2,254})'] = 'view/slug/$1';
Remember to list your routes in order from most specific to least. Wild card matches are less specific than exact matches (like home and activity), so they should come after (below).
Now, that's all the complicated stuff. A little more FYI.
Remember that dashes - have a special meaning when in between [] brackets. You should escape them if you want to match a literal dash.
$route['([A-Za-z0-9][A-Za-z0-9_\-]{2,254})'] = 'view/slug/$1';
Note that your character repetition min/max {2,254} only applies to the second set of characters, so your user names must be 3 characters at minimum, and 255 at maximum. Just an FYI if you didn't realize that already.
I saw your own answer to this problem, and it's just ugly. Sorry. The ^ and $ symbols are used improperly throughout the lookahead (which still shouldn't be there in the first place). It may "work" for a few use cases that you're testing it with, but it will just give you problems and headaches in the future.
Hopefully now you know more about regular expressions and how they're matched in the routing process.
And to answer your question, no, you should not use ^ and $ at the beginning and end of your regex -- CodeIgniter will add that for you.
Use the 404, Luke...
At this point your routes are improved and should be functional. I will throw it out there, though, that you might want to consider using the controller/method defined as the 404_override to handle your wild cards. The main benefit of this is that you don't need ANY routes to direct a wild card, or to prevent your wild card from goofing up existing controllers. You only need:
$route['404_override'] = 'view/slug';
Then, your View::slug() method would check the URI, and see if it's a valid pattern, then check if it exists as a user (same as your slug method does now, no doubt). If it does, then you're good to go. If it doesn't, then you throw a 404 error.
It may not seem that graceful, but it works great. Give it a shot if it sounds better for you.
I'm not familiar with codeIgniter specifically, but most frameworks routing operate based on precedence. In other words, the default controller, 404, etc routes should be defined first. Then you can simplify your regex to only match the slugs.
Ok answering my own question
I've seem to come up with a different expression that works:
$route['(^(?!default_controller$|404_override$|home$|activity$)[A-Za-z0-9][A-Za-z0-9_-]{2,254}$)'] = 'view/slug/$1';
I added parenthesis around the whole expression (I think that's what CodeIgniter matches with $1 on the right) and added a start of line identifier: ^ and a bunch of end of line identifiers: $
Hope this helps someone who may run into this problem later.
I need to match complete dynamic URL to set-up as a goal in Google Analytics. I don't know how to do that. I have searched on Google with no luck.
So here is the case.
When pressed enter button, the goal URL would be different depending on the product selected.
Example:
http://www.somesite.com/footwear/mens/hiking-boots/atmosphere-boot-p7023.aspx?cl=BLACK
http://www.somesite.com/womens/clothing/waterproof-jackets/canyon-womens-long-jacket-p7372.aspx?cl=KHAKI
http://www.somesite.com/travel/accessories/mosquito-nets/mosquito-net-double-p5549.aspx?cl=WHITE
http://www.somesite.com/ski/accessories/ski-socks-tubes/ski-socks-p2348.aspx?cl=BLACK
If you look closely in the URL, you can see that there are three parts:
http://www.somesite.com/{ 1st part }/{ 2nd part }/{3rd part }/{ page URL }/{ querystring param}
So if I manually change page URL part like p2348 to p1234, website will redirect to the proper page:
http://www.somesite.com/kids/clothing/padded-down-jackets/khuno-kids-padded-jacket-p1234.aspx?cl=BLUE
I don't know how to do that. Please help with regular expression to match those 4 digit while p remains there OR help me with those three parts matching any text/number and then 4 digit product code.
You should try this regex. It's the most simple one and functional as well.
p\d{4}
This will return you strings like p7634, p7351, p0872.
If you are not completely sure there will be exactly 4 digits, use the following regex.
p\d*
This one will return you strings like p43, p9165, p012, p456897689 and others.
Try
p[0-9][0-9][0-9][0-9]\.aspx
if there are always 4 digits after the p.
Your attempt
[^p]\d[0-9][0-9]
does not work because [^p] matches anything except for p, and \d[0-9][0-9] matches only three digits instead of four.
I want it to catch things like somedomain.com/folder/path, but not something like domain.sub.other.com. The regex I have so far is almost complete, it just doesn't sift out the multi-domain urls:
^(.*)://(?!(.{2,3})\.(.*)(.{2,3})(.*)
Is there any way to sift out on multiple periods?
Instead of .{2,3}, you want something like this: [^.]{2,3} - this excludes the period (no need to escape as it has no special meaning in this context in a regular expression) from that particular match. Overall you'd have something like:
://[^.]+\.[^.]{2,3}(/.*)?
Except obviously you're missing things like *.info by doing that....
Found a solution that is working given a variety of test scenarios:
^(.*)://([^.]+)\.([^(\?|/|\r|\n|\.)]+)((/|\?|$)+)(.*)$
Here, the 2nd to the last group is matching against a potential forward slash, question mark or end of string, working together with the group before it which does not allow matches which include '.'
So the final effect is that it only matches URLs with a two-part domain such as 'domain.com' and there aren't any limits placed on string length.
Hi I want to be able to set the regular expression to allow for dates to be entered like this
01/01/1900 or 01/01/70, I have the following but not sure how to make it so that it takes 4 or 2 at the end.
^([1-9]|0[1-9]|1[012])[- /.]([1-9]|0[1-9]|[12][0-9]|3[01])[- /.][0-9]{4}$
The other one I would like to know is for URL
This one I have no idea how do I make it so that it matches correct URL's?
Thank you
This should match two our four digit numbers:
\d{2}(\d{2})?
Your full regex would be something like this:
^([1-9]|0[1-9]|1[012])[- /.]([1-9]|0[1-9]|[12][0-9]|3[01])[- /.]\d{2}(\d{2})?$
URLs are hard to test. http://localhost is a valid URL and so it https://test.example.co.uk:443/index.ece?foo=bar. I would look for something in your language to test this for you or do a very simple test like this (you will have to delimit some special chars depending on the regex engine you use):
^https?://
To modify your regex so that it takes either 2 or 4 digits at the end, you can try this:
^([1-9]|0[1-9]|1[012])[- /.]([1-9]|0[1-9]|[12][0-9]|3[01])[- /.]([0-9]{4}|[0-9]{2})$
For URLs, you can try (from here):
(http|https)://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?
or have a look at this S.O. question.
^([1-9]|0[1-9]|1[012])[- /.]([1-9]|0[1-9]|[12][0-9]|3[01])[- /.]([0-9]{4}|[0-9]{2})$
Well, is ([0-9]{4}|[0-9]{2}) not good enough for you? Probably you could add some checking that first two digits in the four-digits group is 19 or 20 but it depends on your needs.
As for URL matching look here. There's many of them with tests.
You can use another alternation in at the end to accept 2 or 4 (the same way you do the "or" options for the other date parts). Alternatively, you can require 2 digits in the last position, and then have 2 optional digits after that.
Unless you need to capture the individual parts (day, month, year), you should use non-capturing parentheses, like this (?:) (that's the .NET syntax).
Finally, you should consider the type of validation that you are trying to achieve with this. It is probably better to enforce the format, and not worry about bad forms like 91/73/9004 because even with what you have you can still get invalid dates, like 02/31/2011. Since you probably have to perform further validation, why not simplify the regex to something like ^(?:\d{1,2}[-/.]){2}\d{2}(?:\d{2})?$
As for URLs, stackoverflow is littered with duplicate questions about this.