I'm trying to filter out some garbage text from a string with regex but can't seem to get it to work. I'm not a regex expert (not even close) and I've searched for similar examples but none that seems to solve my problem.
I need a regex that matches everything from the start of a string to a specific word in that string but not the word itself.
here's an example:
<p>This is the string I want to process with as you can see also contains HTML tags like <i>this</i> and <strong>this</strong></p>
<p>I want to remove everything in the string BEFORE the word "giraffe" (but not "giraffe" itself and keep everything after it.</p>
So, how do I match everything in the string before the word "giraffe"?
Thanks!
resultString = Regex.Replace(subjectString,
#"\A # Start of string
(?: # Match...
(?!""giraffe"") # (unless we're at the start of the string ""giraffe"")
. # any character (including newlines)
)* # zero or more times",
"", RegexOptions.Singleline | RegexOptions.IgnorePatternWhitespace);
should work.
Why regex?
String s = "blagiraffe";
s = s.SubString(s.IndexOf("giraffe"));
Try this:
var s =
#"<p>This is the string I want to process with as you can see also contains HTML tags like <i>this</i> and <strong>this</strong></p>
<p>I want to remove everything in the string BEFORE the word ""giraffe"" (but not ""giraffe"" itself and keep everything after it.</p>";
var ex = new Regex("giraffe.*$", RegexOptions.Multiline);
Console.WriteLine(ex.Match(s).Value);
This code snippet produces the following output:
giraffe" (but not "giraffe" itself and keep everything after it.</p>
A look-ahead would do the trick:
^.*(?=\s+giraffe)
You could used a pattern with a lookahead like this
^.*?(?=giraffe)
Related
In C#, I want to use a regular expression to match any of these words:
string keywords = "(shoes|shirt|pants)";
I want to find the whole words in the content string. I thought this regex would do that:
if (Regex.Match(content, keywords + "\\s+",
RegexOptions.Singleline | RegexOptions.IgnoreCase).Success)
{
//matched
}
but it returns true for words like participants, even though I only want the whole word pants.
How do I match only those literal words?
You should add the word delimiter to your regex:
\b(shoes|shirt|pants)\b
In code:
Regex.Match(content, #"\b(shoes|shirt|pants)\b");
Try
Regex.Match(content, #"\b" + keywords + #"\b", RegexOptions.Singleline | RegexOptions.IgnoreCase)
\b matches on word boundaries. See here for more details.
You need a zero-width assertion on either side that the characters before or after the word are not part of the word:
(?=(\W|^))(shoes|shirt|pants)(?!(\W|$))
As others suggested, I think \b will work instead of (?=(\W|^)) and (?!(\W|$)) even when the word is at the beginning or end of the input string, but I'm not sure.
put a word boundary on it using the \b metasequence.
I have this string
string s = "<textarea>\r\n</textarea>";
And I want to replace the textarea content dynamically, trying it like this:
Regex regex = new Regex("(<textarea.*?>)(.*)(</textarea>)");
string a = regex.Replace(s, "$1new value$3");
Yet this does not procedure the output I want, which should be: <textarea>new value</textarea>. It just produces
<textarea>
</textarea>
How can I fix it?
Use RegexOptions.SingleLine mode. Otherwise . does not match newlines.
According to the documentation:
Singleline Specifies single-line mode. Changes the meaning of the dot
(.) so it matches every character (instead of every character except
\n).
.* will stop when it encounters a \n.
So use RegexOptions.MultiLine option.
Or just change your regex to:
(?m)(<textarea.*?>)(.*)(</textarea>)
(?m) is inline multiline modifier.
Edit:
Sorry It should've been RegexOptions.SingleLine. I was confused since I use regex only in javascript on a large basis.
I have a regex that I've verified in 3 separate sources as successfully matching the desired text.
http://regexlib.com/RETester.aspx
http://derekslager.com/blog/posts/2007/09/a-better-dotnet-regular-expression-tester.ashx,
http://sourceforge.net/projects/regextester/
But, when I use the regex in my code. It does not produce a match. I have used other regex with this code and they have resulted in the desired matches. I'm at a loss...
string SampleText = "starttexthere\r\nothertexthereendtexthere";
string RegexPattern = "(?<=starttexthere)(.*?)(?=endtexthere)";
Regex FindRegex = new Regex(#RegexPattern);
Match m = FindRegex.Match(SampleText);
I don't know if the problem is my regex, or my code.
The problem is that your text contains a \r\n which means it is split across two lines. If you want to match the whole string you have to set the option to match across multiple lines, and to change the behavior of the . to include the \n (new-line character) in matched
Regex FindRegex = new Regex(#RegexPattern, RegexOptions.Multiline | RegexOptions.Singleline);
You don't need RegexOptions.Multiline.
The problem in your case is that the dot matches any character except line break characters (\r\ and \n).
So, you'll need to define your regex pattern like so: (?<=starttexthere)[\w\r\n]+(?=endtexthere) in order to specifically match text across line breaks.
Here's an online running sample: http://ideone.com/ZXgKar
I have the following Regex in C#:
Regex h1Separator = new Regex(#"<h1>(?'name'[\w\d\s]+?)(<br\s?/?>)?</h1>", RegexOptions.Singleline);
Trying to match a string that looks like this:
<h1>test content<br>
</h1>
right now it matches strings that look like the following:
<h1>test content<br></h1>
<h1>test content</h1>
What am I doing wrong? Should I be matching for a newline character? If so, what is it in C#? I can't find one.
You don't check for whitespace between the end of the br tag and the start of the next tag, so it expects to see the hr tag immediately after. Add a \s* in between to allow that.
You have it defined as a single line regex, see the RegexOptions.Singleline flag :) use RegexOptions.Multiline
The newline character in C# is: \n. However, I am not skilled in regex and couldn't tell you what would happen if there was a newline in a regex expression.
you can either add a dot . to your string before the ending </h1> and keep the RegexOptions.Singleline option, or change it to RegexOptions.Multiline and add a $ to the regex before the </h1>. details here
Use the Multiline flag. (Edit to address my mispeaking about the .Net platform).
Singleline mode treats the entire string you are passing in as one entry. Therefore ^ and $ represent the entire string and not the beginning and ending of a line within the string. Example <h1>(?'name'[\w\d\s]+?)(<br\s?/?>)?</h1> will match this:
<h1>test content<br></h1>
Multiline mode changes the meaning of ^ and $ to the beginning and ending of each line within the string (i.e. they will look at every line break).
Regex h1Separator = new Regex(#"<h1>(?'name'[\w\d\s]+?)$(<br\s?/?>)?</h1>", RegexOptions.Multiline);
will match the desired pattern:
<h1>test content<br>
</h1>
In short, you need to tell the regex parser you expect to work with multiple lines. It helps to have a regex designer that speaks your dialect of regex. There are many.
OK, this one is driving me nuts....
I have a string that is formed thus:
var newContent = string.Format("({0})\n{1}", stripped_content, reply)
newContent will display like:
(old text)
new text
I need a regular expression that strips away the text between parentheses with the parenthesis included AND the newline character.
The best I can come up with is:
const string regex = #"^(\(.*\)\s)?(?<capture>.*)";
var match= Regex.Match(original_content, regex);
var stripped_content = match.Groups["capture"].Value;
This works, but I want specifically to match the newline (\n), not any whitespace (\s)
Replacing \s with \n \\n or \\\n does NOT work.
Please help me hold on to my sanity!
EDIT: an example:
public string Reply(string old,string neww)
{
const string regex = #"^(\(.*\)\s)?(?<capture>.*)";
var match= Regex.Match(old, regex);
var stripped_content = match.Groups["capture"].Value;
var result= string.Format("({0})\n{1}", stripped_content, neww);
return result;
}
Reply("(messageOne)\nmessageTwo","messageThree") returns :
(messageTwo)
messageThree
If you specify RegexOptions.Multiline then you can use ^ and $ to match the start and end of a line, respectively.
If you don't wish to use this option, remember that a new line may be any one of the following: \n, \r, \r\n, so instead of looking only for \n, you should perhaps use something like: [\n\r]+, or more exactly: (\n|\r|\r\n).
Actually it works but with opposite option i.e.
RegexOptions.Singleline
You are probably going to have a \r before your \n. Try replacing the \s with (\r\n).
Think I may be a bit late to the party, but still hope this helps.
I needed to get multiple tokens between two hash signs.
Example i/p:
## token1 ##
## token2 ##
## token3_a
token3_b
token3_c ##
This seemed to work in my case:
var matches = Regex.Matches (mytext, "##(.*?)##", RegexOptions.Singleline);
Of course, you may want to replace the double hash signs at both ends with your own chars.
HTH.
Counter-intuitive as it is, you can use both Multiline and Singleline option.
Regex.Match(input, #"(.+)^(.*)", RegexOptions.Multiline | RegexOptions.Singleline)
First capturing group will contain first line (including \r and \n) and second group will have second line.
Why:
First of all RegexOptions enum is flag so it can be combined with bitwise operators, then
Multiline:
^ and $ match the beginning and end of each line (instead of the beginning and end of the input string).
Singleline:
The period (.) matches every character (instead of every character except \n)
see docs