Hi I've been struggling with this for the last hour and am no closer. How exactly do I strip everything except numbers, commas and decimal points from a rails string? The closest I have so far is:-
rate = rate.gsub!(/[^0-9]/i, '')
This strips everything but the numbers. When I try add commas to the expression, everything is getting stripped. I got the aboves from somewhere else and as far as I can gather:
^ = not
Everything to the left of the comma gets replaced by what's in the '' on the right
No idea what the /i does
I'm very new to gsub. Does anyone know of a good tutorial on building expressions?
Thanks
Try:
rate = rate.gsub(/[^0-9,\.]/, '')
Basically, you know the ^ means not when inside the character class brackets [] which you are using, and then you can just add the comma to the list. The decimal needs to be escaped with a backslash because in regular expressions they are a special character that means "match anything".
Also, be aware of whether you are using gsub or gsub!
gsub! has the bang, so it edits the instance of the string you're passing in, rather than returning another one.
So if using gsub! it would be:
rate.gsub!(/[^0-9,\.]/, '')
And rate would be altered.
If you do not want to alter the original variable, then you can use the version without the bang (and assign it to a different var):
cleaned_rate = rate.gsub!(/[^0-9,\.]/, '')
I'd just google for tutorials. I haven't used one. Regexes are a LOT of time and trial and error (and table-flipping).
This is a cool tool to use with a mini cheat-sheet on it for ruby that allows you to quickly edit and test your expression:
http://rubular.com/
You can just add the comma and period in the square-bracketed expression:
rate.gsub(/[^0-9,.]/, '')
You don't need the i for case-insensitivity for numbers and symbols.
There's lots of info on regular expressions, regex, etc. Maybe search for those instead of gsub.
You can use this:
rate = rate.gsub!(/[^0-9\.\,]/g,'')
Also check this out to learn more about regular expressions:
http://www.regexr.com/
I have a requirement to escape a string with url information but also some special characters such as '<'.
Using cl_http_utility=>escape_url this translates to '%3c'. However due to our backend webserver, it is unable to recognize this as special character and takes the value literally. What it does recognize as special character is '%3C' (C is upper case). Also if one checks http://www.w3schools.com/tags/ref_urlencode.asp it shows the value with all caps as the proper encoding.
I guess my question is is there an alternative to cl_http_utility=>escape_url that does essentially the same thing except outputs the value in upper case?
Thanks.
Use the string function.
l_escaped = escape( val = l_unescaped
format = cl_abap_format=>e_url ).
Other possible formats are e_url_full, e_uri, e_uri_full, and a bunch of xml/json stuff too. The string function escape is documented pretty well, demo programs and all.
text.scan(/\"[\d\w\s\+\-\*\/]*\"/)
I'm simply looking to find any thing within quotations that can contain letters, numbers, spaces, plus, minus, star, or forward slash. Everything works great in console. Each of the following works in a browser:
"abc"
"123"
"x-1" or "x - 1"
"x/1" or "x / 1"
But the plus sign and star fail in a browser (despite working fine in console with the same regex). Does anyone have any ideas?
Edit #1: I'm performing a quick gsub to add some formatting to the results of the scan. If the quotations have a plus or star in them, they don't even get picked up by the scan. The same code and text pasted in console works just fine.
Edit #2: I figured out a better way to frame this question without extraneous details and got the answer. "Why can't I perform a gsub on each of the results from a scan if the result contains regex special characters?"
Turned out that this problem was related to regexp string insertion (/#{whatever}/) not escaping special characters - manually escaping clears it up (/#{Regexp.escape(whatever)}/). See this question for a full example/explanation.
I don't know what do you mean "work in browser" but I'm making an assumption that you're trying to parse an URL. In URL the + & * signs can be converted to %2B & %2A respectively.
Try this regexp:
/"[(\d\w\s\+\-\*\/|%2B|%2A)]+"/
...or decode URL before parsing.
I am using Yahoo Pipes to rewrite a URL. Everything is fine but the last 6 characters of the URL need to be removed from all the links.
Ex.
http://www.mysite.com/blahblah/34567
needs to be rewritten to
http://www.mysite.com/blahblah
The number at the end is always changing, so I am hoping to just chop the last 6 characters off of each url.
You'll want the Sub string module. Presuming it functions in a similar way to other languages, you'll want an undefined From value, and a Length value of -6, which should cut 6 characters off the end of the URL.
Seems that a regex in (.*)(.....) and takinq only the first match should do the trick
Background (question further down)
I've been Googling this back and forth reading RFCs and SO questions trying to crack this, but I still don't got jack.
So I guess we just vote for the "best" answer and that's it, or?
Basically it boils down to this.
3.4. Query Component
The query component is a string of information to be interpreted by the resource.
query = *uric
Within a query component, the characters ";", "/", "?", ":", "#", "&", "=", "+", ",", and "$" are reserved.
The first thing that boggles me is that *uric is defined like this
uric = reserved | unreserved | escaped
reserved = ";" | "/" | "?" | ":" | "#" | "&" | "=" | "+" | "$" | ","
This is however somewhat clarified by paragraphs such as
The "reserved" syntax class above refers to those characters that are allowed within a URI, but which may not be allowed within a particular component of the generic URI syntax; they are used as delimiters of the components described in Section 3.
Characters in the "reserved" set are not reserved in all contexts. The set of characters actually reserved within any given URI component is defined by that component. In general, a character is reserved if the semantics of the URI changes if the character is replaced with its escaped US-ASCII encoding.
This last excerpt feels somewhat backwards, but it clearly states that the reserved character set depends on context. Yet 3.4 states that all the reserved characters are reserved within a query component, however, the only things that would change the semantics here is escaping the question mark (?) as URIs do not define the concept of a query string.
At this point I've given up on the RFCs entirely but found RFC 1738 particularly interesting.
An HTTP URL takes the form:
http://<host>:<port>/<path>?<searchpart>
Within the <path> and <searchpart> components, "/", ";", "?" are reserved. The "/" character may be used within HTTP to designate a hierarchical structure.
I interpret this at least with regards to HTTP URLs that RFC 1738 supersedes RFC 2396. Because the URI query has no notion of a query string also the interpretation of reserved doesn't really let allow me to define query strings as I'm used to doing by now.
Question
This all started when I wanted to pass a list of numbers together with the request of another resource. I didn't think much of it, and just passed it as a comma separated values. To my surprise though the comma was escaped. The query page.html?q=1,2,3 encoded turned into page.html?q=1%2C2%2C3 it works, but it's ugly and didn't expect it. That's when I started going through RFCs.
My first question is simply, is encoding commas really necessary?
My answer, according to RFC 2396: yes, according to RFC 1738: no
Later I found related posts regarding the passing of lists between requests. Where the csv approach was poised as bad. This showed up instead, (haven't seen this before).
page.html?q=1;q=2;q=3
My second question, is this a valid URL?
My answer, according to RFC 2396: no, according to RFC 1738: no (; is reserved)
I don't have any issues with passing csv as long as it's numbers, but yes you do run into the risk of having to encode and decode values back and forth if the comma suddenly is needed for something else. Anyway I tried the semi-colon query string thing with ASP.NET and the result was not what I expected.
Default.aspx?a=1;a=2&b=1&a=3
Request.QueryString["a"] = "1;a=2,3"
Request.QueryString["b"] = "1"
I fail to see how this greatly differs from a csv approach as when I ask for "a" I get a string with commas in it. ASP.NET certainly is not a reference implementation but it hasn't let me down yet.
But most importantly -- my third question -- where is specification for this? and what would you do or for that matter not do?
That a character is reserved within a generic URL component doesn't mean it must be escaped when it appears within the component or within data in the component. The character must also be defined as a delimiter within the generic or scheme-specific syntax and the appearance of the character must be within data.
The current standard for generic URIs is RFC 3986, which has this to say:
2.2. Reserved Characters
URIs include components and subcomponents that are delimited by characters in the "reserved" set. These characters are called "reserved" because they may (or may not) be defined as delimiters by the generic syntax, by each scheme-specific syntax, or by the implementation-specific syntax of a URI's dereferencing algorithm. If data for a URI component would conflict with a reserved character's purpose as a delimiter [emphasis added], then the conflicting data must be percent-encoded before the URI is formed.
reserved = gen-delims / sub-delims
gen-delims = ":" / "/" / "?" / "#" / "[" / "]" / "#"
sub-delims = "!" / "$" / "&" / "'" / "(" / ")"
/ "*" / "+" / "," / ";" / "="
3.3. Path Component
[...]
pchar = unreserved / pct-encoded / sub-delims / ":" / "#"
[...]
3.4 Query Component
[...]
query = *( pchar / "/" / "?" )
Thus commas are explicitly allowed within query strings and only need to be escaped in data if specific schemes define it as a delimiter. The HTTP scheme doesn't use the comma or semi-colon as a delimiter in query strings, so they don't need to be escaped. Whether browsers follow this standard is another matter.
Using CSV should work fine for string data, you just have to follow standard CSV conventions and either quote data or escape the commas with backslashes.
As for RFC 2396, it also allows for unescaped commas in HTTP query strings:
2.2. Reserved Characters
Many URI include components consisting of or delimited by, certain
special characters. These characters are called "reserved", since
their usage within the URI component is limited to their reserved
purpose. If the data for a URI component would conflict with the
reserved purpose, then the conflicting data must be escaped before
forming the URI.
Since commas don't have a reserved purpose under the HTTP scheme, they don't have to be escaped in data. The note from § 2.3 about reserved characters being those that change semantics when percent-encoded applies only generally; characters may be percent-encoded without changing semantics for specific schemes and yet still be reserved.
I think the real question is: "What characters should be encoded in a query string?" And that depends mainly on two things: The validity and the meaning of a character.
Validity according to the RFC standard
In RFC3986 we can find which special characters are valid and which are not inside a query string:
// Valid:
! $ & ' ( ) * + , - . / : ; = ? # _ ~
% (should be followed by two hex chars to be completely valid (e.g. %7C))
// Invalid:
" < > [ \ ] ^ ` { | }
space
# (marks the end of the query string, so it can't be a part of it)
extended ASCII characters (e.g. °)
Deviations from the standard
Browsers and web frameworks do not always strictly follow the RFC standard. Below are some examples:
[, ] are not valid, but Chrome and Firefox do not encode these characters inside a query string. The reasoning given by Chrome devs is simply: "If other browsers and an RFC disagree, we will generally match other browsers." QueryHelpers.AddQueryString from ASP.NET Core on the other hand will encode these characters.
Other invalid characters that are not encoded by Chrome and Firefox are:
\ ^ ` { | }
' is a valid character inside a query string but will be encoded by Chrome, Firefox and QueryHelpers nevertheless. The explanation given by Firefox devs is that they knew that they don't have to encode it according to the RFC standard, but did it to reduce vulnerabilities.
Special meaning
Some characters are valid and also don't get encoded by browsers, but should still be encoded in certain cases.
+: Spaces are normally encoded as %20 but alternatively they can be encoded as +. So + inside a query string means it's an encoded space. If you want to include a character that's actually supposed to literally mean plus, then you have to use the encoded version of + which is %2B.
~: Some old Unix systems interpreted URI parts that started with ~ as a path to a home directory. So it's a good idea to encode ~ if it's not meant to denote the start of a Unix home directory path for an old system (so nowadays probably always encode).
=, &: Usually (although RFC doesn't specify that this is required) query strings contain parameters in the format "key1=value1&key2=value2". If that's the case and =s or &s should be part of the parameter key or the parameter value instead of giving them the role of separating the key and value or separating the parameters, then you have to encode those =s and &s. So if a parameter value should for some reason consist of the string "=&" then it has to be encoded as %3D%26 which then can be used for the full key and value: "weirdparam=%3D%26".
%: Usually web frameworks figure out that %s that are not followed by two hex characters simply mean the % itself, but it's still a good idea to always encode % when it's supposed to only mean % and not indicate the start of an encoded character (e.g. %7C) because RFC3986 specifies that % is only valid when followed by two hex characters. So don't use "percentageparam=%" use "percentageparam=%25" instead.
Encoding guidelines
Encode every character that is otherwise invalid* according to RFC3986 and every character that can have special meaning but should only be interpreted in a literal way without giving it a special meaning. You can also encode things that aren't required to be encoded, like '. Why? Because it doesn't hurt to encode more than necessary. Servers and web frameworks when parsing a query string will decode every encoded character, no matter if it was really necessary to previously encode that character or not.
The only characters of a query string that shouldn't be encoded are those that can have a special meaning and shouldn't lose that special meaning, e.g. don't encode the = of "key1=value1". For that to achieve don't apply an encoding method to the whole query string (and also not to the whole URI) but apply it only and separately to the query parameter keys and values. For example, with JS:
var url = "http://example.com?" + encodeURIComponent(myKey1) + "=" + encodeURIComponent(myValue1) + "&" + encodeURIComponent(myKey2)...;
Note that encodeURIComponent encodes a lot more characters than necessary meaning characters that are valid in a query string and don't have special meaning there e.g. /, ?, ...
The reason is that encodeURIComponent wasn't created for query strings alone but instead encodes characters that have special meaning outside of the query string as well, e.g. / for the path URI component. QueryHelpers.AddQueryString works in a similar manner. Under the hood it uses System.Text.Encodings.Web.DefaultUrlEncoder which is not just meant for query strings but also for isegment, ipath-noscheme and ifragment.
* You could probably get away with only regarding those characters as invalid that are both not allowed by the RFC and that are also always encoded by Chrome for instance. This would be Space " < >. But it's probably better to be on the safer side and encode at least everything that RFC3986 considers invalid.
OP's questions
My first question is simply, is encoding commas really necessary -> No it's not necessary, but it doesn't hurt (except ugliness) and will happen with default encoding methods e.g. encodeURIComponent and decoding and query string parsing should work nevertheless.
My second question, is this a valid URL (page.html?q=1;q=2;q=3)? -> It's RFC valid, but your server / web framework might have a hard time parsing the query string when it might expect the typical "key1=value1&key2=value2" format for query strings.
Where is specification for this? -> There isn't a single specification that covers everything because some things are implementation specific. For instance there are different ways of specifying arrays inside of query strings.
Just use ?q=1+2+3
I am answering here a fourth question :) that did not ask but all started with: how do i pass list of numbers a-la comma-separated values? Seems to me the best approach is just to pass them space-separated, where spaces will get url-form-encoded to +. Works great, as longs as you know the values in the list contain no spaces (something numbers tend not to).
page.html?q=1;q=2;q=3
is this a valid URL?
Yes. The ; is reserved, but not by an RFC. The context that defines this component is the definition of the application/x-www-form-urlencoded media type, which is part of the HTML standard (section 17.13.4.1). In particular the sneaky note hidden away in section B.2.2:
We recommend that HTTP server implementors, and in particular, CGI implementors support the use of ";" in place of "&" to save authors the trouble of escaping "&" characters in this manner.
Unfortunately many popular server-side scripting frameworks including ASP.NET do not support this usage.
I would like to note that page.html?q=1&q=2&q=3 is a valid url as well. This is a completely legitimate way of expressing an array in a query string. Your server technology will determine how exactly that is presented.
In Classic ASP, you check Response.QueryString("q").Count and then use Response.QueryString("q")(0) (and (1) and (2)).
Note that you saw this in your ASP.NET, too (I think it was not intended, but look):
Default.aspx?a=1;a=2&b=1&a=3
Request.QueryString["a"] = "1;a=2,3"
Request.QueryString["b"] = "1"
Notice that the semicolon is ignored, so you have a defined twice, and you got its value twice, separated by a comma. Using all ampersands Default.aspx?a=1&a=2&b=1&a=3 will yield a as "1,2,3". But I am sure there is a method to get each individual element, in case the elements themselves contain commas. It is simply the default property of the non-indexed QueryString that concatenates the sub-values together with comma separators.
I had the same issue. The URL that was hyperlinked was a third party URL and was expecting a list of parameters in format page.html?q=1,2,3 ONLY and the URL page.html?q=1%2C2%2C3 did not work. I was able to get it working using javascript. May not be the best approach but can check out the solution here if it helps anyone.
If you are sending the ENCODED characters to FLASH/SWF file, then you should ENCODE the character twice!! (because of Flash parser)