I have a regex expression which searches for strings using a Prefix and a Suffix. In it's simplest form \$\$\w+\$\$ will find $$My_Name$$ (in this case the Prefix and Suffix are both equal to $$) Another example would be \[\#\w+\#\] to match [#My_Name#].
The Prefix and Suffix will always be a specific string of 0 to n characters which I can always safely escape for a direct character match.
I extract the Matches in my C# code so I can work with them but obviously my match contains $$My_Name$$ but what I want is to simply get the inner string between the Suffix and Prefix: My_Name.
How do I exclude the Prefix and Suffix from the result?
Change your REGEX to \$\$(\w+)\$\$ and use $1 to get the matching (inner) string.
For example
string pattern = #"\$\$(\w+)\$\$";
string input = "$$My_Name$$";
Regex rgx = new Regex(pattern);
Match result = rgx.Match(input);
Console.WriteLine(result.Groups[1]);
Outputs: "My Name"
P.S - There's no need to use explicitly typed local variables, but I just wanted the types to be clear.
You can group your w+ into a group like this (w+) then when you retrieve the matched string you might be able to ask for that subgroup.
I do not know if I am wrong (but you didn't provided any code whatsoever) but I think this is how it is done: .Groups[1].Value on the the result of Regex.Match.
How about the regex below. It works by capturing the first character into a named group then capturing any repeats into a named group called first group which it then uses to match the end of the string. It will work with any number of repeated character so long as they repeated at the end of the word.
'(?<first_group>(?<first_char>.)\k<first_char>+)(?<word>\w+)\k<first_group>+'
You just need to then extract the capture group named word like so:
String sample = "$$My_Name$$";
Regex regex = new Regex("(?<first_group>(?<first_char>.)\k<first_char>+)(?<word>\w+)\k<first_group>+");
Match match = regex.Match(sample);
if (match.Success)
{
Console.WriteLine(match.Groups["word"].Value);
}
You can use named group like this:
(\$\$)(?<group1>.+?)\1 -- pattern 1 (first case)
\[(#)(?<group2>.+?)\1\] -- pattern 2 (second case)
or combined representation would be:
(\$\$)(?<group1>.+?)\1|\[(#)(?<group2>.+?)\3\]
I would suggest you to use .+? it will help you to match any character other than your prefix/suffix.
Live Demo
Related
I am trying to use Regex to count the number of times a certain string appears in another comma-separated string.
I am using Regex.Matches(comma-separated string, certain string).Count to grab the number. The only issue I have is that I want it to simply count as a match if it lines up at the start of the string.
For instance, if I have the comma separated string
string comma_separated = "dog,cat,bird,blackdog,dog(1)";
and want to see how many times the search string matches with the contents of the comma-separated string
string search = "dog";
I use:
int count = Regex.Matches(comma_separated, search).Count;
I would expect it to be 2 since it matches up with
"dog,cat,bird,blackdog,dog(1)",
however it returns a 3 since it is also matching up with the dog part of blackdog.
Is there any way I can get it to only count as a match when it recognizes a match starting at the start of the string? Or am I just using Regex incorrectly?
As noted in the comments, a regex may not be the most logical way for you to achieve your desired result. However, if you would like to use a regex to find your matches, something like this would provide your desired result
(?<=,|^)dog
This will perform a "positive lookbehind" to ensure that the word "dog" is preceded by either a comma or is at the start of the string you are searching.
More info available on lookarounds in Regex here: https://www.regular-expressions.info/lookaround.html
string comma_separated = "dog,cat,bird,blackdog,dog(1)";
int count = Regex.Matches(comma_separated, string.Format(#"\b{0}\b", Regex.Escape("dog")), RegexOptions.IgnoreCase).Count;
By appending the \b to either side of the text you can find the "EXACT" match within the text.
Try using this pattern: search = #"\bdog";. \b matches word boundary.
I am really struggling with RegEx. I want my RegEx (if possible) to do 2 things:
1- Validate that the whole string respects the format NAME_STKBYGRP.CSV
2- Extract the NAME substring if match
Examples:
TEST_STKBYGRP.CSV -> TEST
other_stkbygrp.csv -> other
test_wrong.csv -> ""
Here is what I tried so far
string input = "NAME_STKBYGRP.CSV";
Regex regex = new Regex("([A-Z])*_STKBYGRP.CSV", RegexOptions.IgnoreCase);
string s = regex.Match(input).Value;
It does return "" if it doesn't match but return the whole input if it matches.
You need to read regex.Match(input).Groups[1].Value if you only want the value of the first group.
You should also add a ^ and $ at the start and end of your regex if you want to rule out strings like evilnumber12345_NAME_STKBYGRP.CSVevilsuffix.
Edit: adv12 also has a good point about the location of the * - it should be inside the parentheses.
First off, your * should be inside the parentheses. Otherwise, you'll capture several single-character groups. Then, use Match.Groups[1] to get just the characters matched by the portion of the regex in the parentheses.
I am trying to replace some content using regular expression and not able to do it, can you please have a look..
My Input: <Tag>E2iamjunkblabla</Tag>
Expected Output: <Tag>E2done</Tag>
I am trying this:
string input = "<Tag>E2iamjunkblabla</Tag>";
string output= System.Text.RegularExpressions.Regex.Replace(input, "<Tag>E2*</Tag>", "<Tag>E2done</Tag>");
What am I doing wrong? Also is there any way to retain first 3 characters(numbers or alphbets) after E2?
I mean the output should be
<Tag>E2iam</Tag>
Sounds like you want this:
string input = "<Tag>E2iamjunkblabla</Tag>";
string output = System.Text.RegularExpressions.Regex.Replace(input, "<Tag>E2(...).*</Tag>", #"<Tag>E2$1done</Tag>");
To break it down:
The match:
Match <Tag> then match E2 then match any character 3 times (...) (the parenthesis mean to store that capture in a group), then match any character zero or more times .* followed by the literal </Tag>
The replace:
Replace the value with <Tag>E2 then the value of capture group 1 $1 then the literal done</Tag>
Let me know if you have issues - and read up on regex! (oh and there are probably a load of ways to do this, this is just one of them)
I want to use regular expressions for analyzing a url, but I can't get the regex groups as I would expect them to be.
My regular expression is:
#"member/filter(.*)(/.+)*"
The strings to match:
"member/filter-one"
"member/filter-two/option"
"member/filter-three/option/option"
I expect to get the following groups:
member/filter-one, /filter-one
member/filter-two/option, /filter-two, /option
member/filter-three/option/option, /filter-three, /option(with 2 captures)
I get the result for the first string, but fore the 2 others I get:
member/filter-two/option, /filter-two/option, empty string
member/filter-three/option/option, /filter-three/option/option, empty string
What can be the issue?
Try
#"member/filter([^/]*)(/.+)*"
Another way could be to use the MatchCollection this way:
string url = "member/filter-three/option/option";
url = url.Replace("member/filter-", string.Empty); // cutting static content
MatchCollection matches = new Regex(#"([^/]+)/?").Matches(url);
foreach (Match match in matches)
{
Console.WriteLine(match.Groups[1].Value);
}
Console.ReadLine();
Here, you first remove the constant part from your string (it could be a parameter of a function). Then you simply check for everything inside two / characters. You do that by identifying [^/] as the character you want to match, which means match one character, that is not a /, then put an identifier after that (+ sign), which means, match more than one character.
The "member/filter([^/]*)(/.+)*" seems logical but is impractical as it accepts empty options (i.e. member/filter1/////////). A more accurate-practical pattern which also allows you to accept more than one filter with options is member(/filter[^/]+(/[^/]+)*)*
I've been playing around with retrieving data from a string using regular expression, mostly as an exercise for myself. The pattern that I'm trying to match looks like this:
"(SomeWord,OtherWord)"
After reading some documentation and looking at a cheat sheet I came to the conclusion that the following regex should give me 2 matches:
"\((\w),(\w)\)"
Because according to the documentation the parenthesis should do the following:
(pattern) Matches pattern and remembers the match. The matched
substring can be retrieved from the resulting Matches collection,
using Item [0]...[n]. To match parentheses characters ( ), use "\ (" or
"\ )".
However using the following code (removed error checking for conciseness) matches quite something different:
string line = "(A,B)";
string pattern = #"\((\w),(\w)\)";
MatchCollection matches = Regex.Matches(line, pattern);
string left = matches[0].Value;
string right = matches[1].Value;
Now I would expect left to become "A" and right to become "B". However left becomes "(A,B)" and there is no second match at all. What am I missing here?
(I know this example is trivial to solve without regexes but to learn how to properly use regexes I should be able to make something simple as this work)
You want the Groups member of the first match. In your example case there is only 1 match, which is the whole string. In the Groups collection you will have 3 items. Try this sample code, left should be A, and right should be B. If you look at the group[0] value it will be the whole string.
string line = "(A,B)";
string pattern = #"\((\w),(\w)\)";
MatchCollection matches = Regex.Matches(line, pattern);
GroupCollection groups = matches[0].Groups;
string left = groups[1].Value;
string right = groups[2].Value;
\w matches only one word character. If words have to contain at least one character, the expression should be:
string pattern = #"\((\w+),(\w+)\)";
if words may be empty:
string pattern = #"\((\w*),(\w*)\)";
+: means one or more repetitions.
*: means zero, one or more repetitions.
In any case, you will get one match with three groups, the first containing the whole string including the left and right parentheses, the two others the two words.
I think the problem is that you're confusing the concept of a match and a group.
A MatchCollection contains a list of strings that matched your entire regex, not just the parenthetical groups inside that Regex. For example, if the string you searched looked like this...
(A,B)(C,D)
...then you would have two matches: (A,B) and (C,D).
However, there's good news: you can get the groups from each match very easily, like so:
string line = "(A,B)";
string pattern = #"\((\w),(\w)\)";
MatchCollection matches = Regex.Matches(line, pattern);
string left = matches[0].Groups[1].Value;
string right = matches[0].Groups[2].Value;
That Groups variable is a collection of parenthetical groups from a single match.
Edit:
Olivier Jacot-Descombes made a very good point: we all got so hung up explaining match vs. group that we forgot to notice a second problem: \w will only match a SINGLE character. You need to add a quantifier (such as +) in order to grab more than one character at a time. Olivier's answer should explain that part clearly.
First off, it's one "match", with 2 "groups"...
I would recommend you name the groups anyway...
string pattern = #"\((?<FirstWord>\w+),(?<SecondWord>\w+)\)";
Then you could do...
Match m = Regex.Match(line, pattern);
string firstWord = m.Groups["FirstWord"].Value;
Since all you are looking for are the characters separated by a comma, you can simply use \w as your pattern. The matches will be A and B.
A handy site for testing your Regex is http://gskinner.com/RegExr/