I need to use regex to search through an html file and replace href="pagename" with href="pages/pagename"
Also the href could be formatted like HREF = 'pagename'
I do not want to replace any hrefs that could be upper or lowercase that begin with http, ftp, mailto, javascript, #
I am using c# to develop this little app in.
HTML manipulation through Regex is not recommended since HTML is not a "regular language." I'd highly recommend using the HTML Agility Pack instead. That gives you a DOM interface for HTML.
I have not tested with many cases, but for this case it worked:
var str = "href='page' href = 'www.goo' href='http://' href='ftp://'";
Console.WriteLine(Regex.Replace(str, #"href ?= ?(('|"")([a-z0-9_#.-]+)('|""))", "x", RegexOptions.IgnoreCase));
Result:
"x x href='http://' href='ftp://'"
You better hold backup files before running this :P
There are lots of caveats when using a find/replace with HTML and XML. The problem is, there are many variations of syntax which are permitted. (and many which are not permitted but still work!)
But, you seem to want something like this:
search for
([Hh][Rr][Ee][Ff]\s*=\s*['"])(\w+)(['"])
This means:
[Hh]: any of the items in square-brackets, followed by
\s*: any number of whitespaces (maybe zero),
=
\s* any more whitespaces,
['"] either quote type,
\w+: a word (without any slashes or dots - if you want to include .html then use [.\w]+ instead ),
and ['"]: another quote of any kind.
replace with
$1pages/$2$3
Which means the things in the first bracket, then pages/, then the stuff in the second and third sets of brackets.
You will need to put the first string in #" quotes, and also escape the double-quotes as "".
Note that it won't do anything even vaguely intelligent, like making sure the quotes match. Warning: try never to use as "any character" (.) symbol in this kind of regex, as it will grab large sections of text, over and including the next quotation mark, possibly up to the end of the file!
see a regex tutorial for more info, e.g. http://www.regular-expressions.info/dotnet.html
Related
I want to find the href from an achore tag. So I have used regex as
<a\s*[^>]*\s*href\s*\=\s*([^(\s*|\>)]*)\s*[^>]*>\s*Text\s*<\/a>
Options = Ignorecase + singleline
Example
Text
So Group[1]="/abc/xzy/pqr.com"
But If the content is like
<a href="/abc/xzy/ //Contains new line
pqr.com" class="m">Text</a>
so Group[1]="/abc/xzy/
So I want to know how to get "/abc/xzy/pqr.com" if the content contains new line(\r\n)
Your capture group is a bit weird: [^(\s*|\>)]* is a character class and it will match any character not (, ror a character class \s, nor an asterisk *, etc.
What you can do however is to put quotes before and after the capture group:
<a\s*[^>]*\s*href\s*\=\s*"([^(\s*|\>)]*)"\s*[^>]*>\s*Text\s*<\/a>
^ ^
And then change the character class to [^"] (not quotes):
<a\s*[^>]*\s*href\s*\=\s*"([^"]*)"\s*[^>]*>\s*Text\s*<\/a>
^^^^
regex101 demo.
This said, it would be better to use a proper html parser instead of regex. It's just that it's more tedious to make a suitable regex because you can forget about a lot of different scenarios, but if you're certain of how your data comes through, regex might be a quick way to get what you need.
If you want to consider single quotes and no quotes at all in some cases, you might try this instead:
<a\s*[^>]*\s*href\s*=\s*((?:[^ ]|[\n\r])+)\s*[^>]*>\s*Text\s*<\/a>
Updated regex101.
This regex has this part instead (?:[^ ]|[\n\r])+ which accepts non-spaces and newlines (and carriage returns just in case). Note that \s contains white spaces, tabs, newlines and form-feed.
I have a URL pattern that needs to contain either APPLES or ORANGES in it, no other value. Optionally, it can also have query parameters. I've tried a number of RegEx patterns, but I just can't get a pattern that will respect the strict match.
Sample URLs
Good
http://www.website.com/en/pages/APPLES
http://www.website.com/en/pages/APPLES?k=v
http://www.website.com/en/pages/ORANGES?k=v&k2=v2
http://www.website.com/en/pages/ORANGES
Bad
http://www.website.com/en/pages/APPLES???k=v
http://www.website.com/en/pages/APPLES?k=v=v
http://www.website.com/en/pages/APPLESORANGES
http://www.website.com/en/pages/1APPLES
http://www.website.com/en/APPLES
Attempted RegEx Patterns (well, at least the best attempts)
(http://*.*.website*.*.com/*.*/pages(/APPLES)|(/ORANGES)[\?]*.*)
(http://*.*.website*.*.com/*.*/pages(/APPLES|/ORANGES)[\?]*.*)
If you're curious, I intentionally want to allow any sub-domain, suffix after "website" (for different environments), and any path between .com/ and /pages, hence the use of . in a number of places.
What would be the best way to achieve this?
**Edit: Final Answer**
My final answer was merged from mathematical.coffee and fardjad.
^https?://.*\.website\b.*\.com/.*/pages/(APPLES\b|ORANGES\b)((\?\w+=\w+)(&?\w+=\w+)*)?$
The single limitation I've discovered is that it will not allow a few valid characters (.~_-%+) in the query string parameter key=value pairs (see: http://en.wikipedia.org/wiki/Query_string#Structure). This isn't an issue for me as I'm matching against a string returned from .NET's Uri class, so I know the URL is well-formed overall.
I think the *.* should be .*:
http://.*\.website\b.*\.com/.*/pages/PAGE[12](\?[^=]+=[^&=]+(&[^=]+=[^=&]+)*)?
Explanation:
http:// # just http://
.*\. # any thing, just make sure it's followed by '.'
website\b # website, the whole word
.*\.com # anything between website and .com
/.*/pages/ # anything between the .com and the pages
PAGE[12] # PAGE1 or PAGE2
(\? # opening bracket and '?' (query string)
[^=]+ # the key: i've said it can't include =
= # =
[^=&]+ # the value: i've said it can't include = or &
(& # opening bracket and '&' for next part of query string
[^=]+=[^=&]+ # key=value pair, same regex as before
)* # 0 or more of these (the &key=value)
)? # the entire query string is optional.
NOTE - there are usually problems parsing query strings with regex and making sure it's a syntactically valid regex.
For example, in the regex I supplied above, I've said that the value in &key=value can't have an ampersand in it. But it could be an escaped entity, like &, which is legal.
You'll always suffer from this sort of problem when you try to parse syntax with regex. It's a risk you'll have to take.
Alternatively, I am sure there is a C# module to parse URLs (many other languages have these), and they take care of all these special cases for you.
Try this:
^https?://(www\.)?\w+[^/]+(/\w+(?=/)){2}/(PAGE1|PAGE2)((\?\w+=\w+)(&?\w+=\w+)*)?$
I'm currently facing a (little) blocking issue. I'd like to replace a substring by one another using regular expression. But here is the trick : I suck at regex.
Regex.Replace(contenu, "Request.ServerVariables("*"))",
"ServerVariables('test')");
Basically I'd like to replace whatever is between the " by "test". I tried ".{*}" as a pattern but it doesn't work.
Could you give me some tips, I'd appreciate it!
There are several issues you need to take care of.
You are using special characters in your regex (., parens, quotes) -- you need to escape these with a slash. And you need to escape the slashes with another slash as well because we 're in a C# string literal, unless you prefix the string with # in which case the escaping rules are different.
The expression to match "any number of whatever characters" is .*. In this case, you would want to match any number of non-quote characters, which is [^"]*.
In contrast to (1) above, the replacement string is not a regular expression so you don't want any slashes there.
You need to store the return value of the replace somewhere.
The end result is
var result = Regex.Replace(contenu,
#"Request\.ServerVariables\(""[^""]*""\)",
"Request.ServerVariables('test')");
Based purely on my knowledge of regex (and not how they are done in C#), the pattern you want is probably:
"[^"]*"
ie - match a " then match everything that's not a " then match another "
You may need to escape the double-quotes to make your regex-parser actually match on them... that's what I don't know about C#
Try to avoid where you can the '.*' in regex, you can usually find what you want to get by avoiding other characters, for example [^"]+ not quoted, or ([^)]+) not in parenthesis. So you may just want "([^"]+)" which should give you the whole thing in [0], then in [1] you'll find 'test'.
You could also just replace '"' with '' I think.
Taryn Easts regex includes the *. You should remove it, if it is just a placeholder for any value:
"[^"]"
BTW: You can test this regex with this cool editor: http://rubular.com/r/1MMtJNF3kM
I'm trying to parse an HTML file for strings in this format:
MyUsername O22</td>
I want to retrieve the information where "305157", "MyUsername" and the first letter in "O22" (which can be either T, K or O).
I'm using this regex; \w* \w\d\d and it works fine, as long as there aren't any åäöÅÄÖ's where the "\w" are.
What should I do?
You can use a character class which specifically includes those things:
[\wåäöÅÄÖ]*
Or you can use the Unicode character class for letters:
\p{L}
or specifically for Latin:
\p{InBasicLatin}
You can use \p{L} to match any 'letter', which will support all letters in all languages, as suggested in this SO question.
Or, you can simply replace \w* with [^<]*, to match all characters that are not the opening of an HTML tag.
But as said by others, parsing HTML using regex is a first step towards insanity...
Firstly: DON'T USE REGULAR EXPRESSIONS TO PARSE HTML. USE AN HTML PARSER.
Secondly: if you really want to do this (and you don't) then instead of \w you could match any character apart from '<':
[^<]* \w\d\d
This is the sample
"abc","abcsds","adbc,ds","abc"
Output should be
abc
abcsds
adbc,ds
abc
Try this:
"(.*?)"
if you need to put this regex inside a literal, don't forget to escape it:
Regex re = new Regex("\"(.*?)\"");
This is a tougher job than you realize -- not only can there be commas inside the quotes, but there can also be quotes inside the quotes. Two consecutive quotes inside of a quoted string does not signal the end of the string. Instead, it signals a quote embedded in the string, so for example:
"x", "y,""z"""
should be parsed as:
x
y,"z"
So, the basic sequence is something like this:
Find the first non-white-space character.
If it was a quote, read up to the next quote. Then read the next character.
Repeat until that next character is not also a quote.
If the next (non-whitespace) character is not a comma, input is malformed.
If it was not a quote, read up to the next comma.
Skip the comma, repeat the whole process for the next field.
Note that despite the tag, I'm not providing a regex -- I'm not at all sure I've seen a regex that can really handle this properly.
This answer has a C# solution for dealing with CSV.
In particular, the line
private static Regex rexCsvSplitter = new Regex( #",(?=(?:[^""]*""[^""]*"")*(?![^""]*""))" );
contains the Regex used to split properly, i.e., taking quoting and escaping into consideration.
Basically what it says is, match any comma that is followed by an even number of quote marks (including zero). This effectively prevents matching a comma that is part of a quoted string, since the quote character is escaped by doubling it.
Keep in mind that the quotes in the above line are doubled for the sake of the string literal. It might be easier to think of the expression as
,(?=(?:[^"]*"[^"]*")*(?![^"]*"))
If you can be sure there are no inner, escaped quotes, then I guess it's ok to use a regular expression for this. However, most modern languages already have proper CSV parsers.
Use a proper parser is the correct answer to this. Text::CSV for Perl, for example.
However, if you're dead set on using regular expressions, I'd suggest you "borrow" from some sort of module, like this one:
http://metacpan.org/pod/Regexp::Common::balanced