i want to capture only the first match through the expression
<p>.*?</p>
i have tried <p>.*?</p>{1} but it is not working it returns all the p tags which are in the html document, please help
It looks like you are using a method which returns every match in the string given a regex, that being the case you need to anchor the regex to the beggining of the string so it doesn't return every match, but only the first one:
^.*?<p>.*?</p>
Use parentheses to capture what you want to capture.
PS: Here goes the standard 'avoid using regex to parse HTML, use a proper HTML parser' advice. This simple regex will fail for nested <p> sections (which I don't recall if are valid in HTML, but still you can probably get them even if they aren't).
The Regex.Match method does this by default, and the regular expression is correct.
Regex regex = new Regex("<p>(.*?)</p>");
Match match = regex.Match("<p>1</p><p>2</p>");
Console.WriteLine("{0}", match.Value);
Running this program will print 1.
Related
/((?:(?:is|will) (?!is))[^<?]+)/i
Test sentences:
text can be infront, Will is a good guy?
same here. Will you be able to help me?
I dont want it to match the first sentence and I want it to match the second.(which it does atm)
I am trying to learn how I can return the whole regex as false if the word after "is|will" is "is", but it keeps matching and eventually finds a match in example number one. I am kind of new to regex, so all help is appreciated.
This is what the match looks like:
Thanks in advance
Your expression seems fine, but you need to anchor it so that it starts matching from the beginning of the text. You can use ^ at the start of the regex.
/^((?:(?:is|will) (?!is))[^<?]+)/i
Without the anchor, the regex engine tries to find a match anywhere in the string. In the case of the first sentence, it can match the word is as the first word in the expression, and then the rest of the expression matches.
I am attempting to write a regular expression in a C# application to find "{value}", along with a backreference to the text before it up to "[[", and another backreference to the text after it up to "]]". For example:
This is some text [[backreference one {value}
backreference two]]
Would match "[[backreference one ", "{value}", and "\r\nbackreference two]]".
I have tried modified versions of the following with no luck. I believe I am missing word boundaries, and may be having trouble because of "{" in the text I am trying to find.
\[\[(^[\{value\}]+)\{value\}(^\]\]+)\]\]
I'm not sure if it would be possible with regular expressions, but it would be ideal if it could find the matching closing bracket, for example the following would find "[[backreferenc[[e]] one ", "{value}", and "ba[[ckref[[e]]rence t]]wo]]":
This is some text [[backreferenc[[e]] one {value}
ba[[ckref[[e]]rence t]]wo]]
You need to use the MatchEvaluator on Regex replace. Also it would make your life easier by breaking up the matches into named capture groups to help with the match evaluator processing. Let me explain.
What the MatchEvaluator does, is it allows one to intercede in the match process with a C# delegate and return what should be replaced when a match happens by examining the actual match captured. That way you can do your text processing as needed.
Here is a basic example where it handles the sections in a basic way, but the structure is there to add your business logic:
string text = #"This is some text [[Name: {name}]] at [[Address: {address}]].";
Regex.Replace(text,
#"(?:\[\[)(?<Section>[^\:]+)(?:\:)(?<Data>[^\]]+)(?:\]\])",
new MatchEvaluator((mtch) =>
{
if (mtch.Groups["Section"].Value == "Name")
return "Jabberwocky";
return "120 Main";
}));
The result of Regex Replace is:
This is some text Jabberwocky at 120 Main.
To the first part of you question try this:
\[\[(.*)({value})(.*)\]\]
I ran into a problem with my regular expressions, I'm using regular expressions for obtaining data from the string below:
"# DO NOT EDIT THIS MAIL BY HAND #\r\n\r\n[Feedback]:hallo\r\n\r\n# DO NOT EDIT THIS MAIL BY HAND #\r\n\r\n"
So far I got it working with:
String sFeedback = Regex.Match(Message, #"\[Feedback\]\:(?<string>.*?)\r\n\r\t\n# DO NOT EDIT THIS MAIL BY HAND #").Groups[1].Value;
This works except if the header is changed, therefore I want the regex to read from [feedback]: to the end of the string. (symbols, ascii, everything..)
I tried: \[Feedback]:(?<string>.*?)$
Above regular expression does work in some regular expression builders online but in my c# code its not working and returns a empty string. What's wrong?
The problem is that . doesn't match newlines unless you use RegexOptions.Singleline when compiling the regex or inline it using (?s):
(?s)\[Feedback\]:(.*)$
You are missing the escape character.
Also, since you are not referring to the group by name in your C# code, you could further simplify your regex to this
\[Feedback\]:(.*)$
$ in regex means:
The match must occur at the end of the string or before \n at the end of the line or string.
and . means:
Matches any single character except \n.
try to use this simple regex:
\[Feedback\]:(?<string>.*)
I'm trying to parse html page and I use the following regular expression:
var regex = new Regex(#"<tag1 id=.id1.>.*<tag2>", RegexOptions.Singleline);
"tag1 id =.id.1" occurs in document only once. "tag2" occurs nearly 50 times after the occurance of "tag 1". But when I try to match page code with my regular expression, it returns only 1 match. Moreover, when I change RegexOptions to "None" or "Multiline" no matches are returned. I'm very confused about this and would appreciate any help.
Leaving aside the obvious exhortations about not using regex to parse HTML, I can explain to you why you're seeing what you're seeing.
If tag1 occurs in your text only once, then the regex can only match it once, so there can never be more than one match. Regular expression matches "consume" the text they have matched, so the next match attempt starts at the end of the last successful match.
This leads to the next problem: .* is greedy, so it matches (with RegexOptions.Singleline) until the end of the string and then backtracks until the last <tag2> it finds in order to allow a successful match. Which is another reason why you only get one match.
As for your second question: Why do the matches go away if you don't use RegexOptions.Singleline? Simple: Without that option, the dot . cannot match newlines, and there appears to be at least one newline between tag1 and the first tag2.
Parsing Html with RegEx is a very bad idea and its unreliable because there still exists a lot of "broken html" in the world. To parse HTML, I would suggest using the HTML Agility Pack. It is an excellent library for parsing HTML and I never had an issue with any HTML I've fed into it.
If I use this
string showPattern = #"return new_lightox\(this\);"">[a-zA-Z0-9(\s),!\?\-:'&%]+</a>";
MatchCollection showMatches = Regex.Matches(pageSource, showPattern);
I get some matches but I want to get rid of [a-zA-Z0-9(\s),!\?\-:'&%]+and use any char .+
but if do this I get no match at all.
What am I doing wrong?
By default "." does not match newlines, but the class \s does.
To let . match newline, turn on SingleLine/DOTALL mode - either using a flag in the function call (as Abel's answer shows), or using the inline modifier (?s), like this for the whole expression:
"(?s)return new_lightox\(this\);"">.+</a>"
Or for just the specific part of it:
"return new_lightox\(this\);"">(?s:.+)</a>"
It might be better to take that a step further and do this:
"return new_lightox\(this\);"">(?s:(?!</?a).+)</a>"
Which should prevent the closing </a> from belonging to a different link.
However, you need to be very wary here - it's not clear what you're doing overall, but regex is not a good tool for parsing HTML with, and can cause all sorts of problems. Look at using a HTML DOM parser instead, such as HtmlAgilityPack.
You're matching a tag, so you probably want something along these lines, instead of .+:
string showPattern = #"return new_lightox\(this\);"">[^<]+</a>";
The reason that the match doesn't hit is possibly because you are missing the multiline/singleline flag and the closing tag is on the next line. In other words, this should work too:
// SingleLine option changes the dot (.) to match newlines too
MatchCollection showMatches = Regex.Matches(
pageSource,
showPattern,
RegexOptions.SingleLine);