Develop Reference

c# regex clarification [duplicate]

What is the regular expression (in JavaScript if it matters) to only match if the text is an exact match? That is, there should be no extra characters at other end of the string.
For example, if I'm trying to match for abc, then 1abc1, 1abc, and abc1 would not match.

Use the start and end delimiters: ^abc$

It depends. You could
string.match(/^abc$/)
But that would not match the following string: 'the first 3 letters of the alphabet are abc. not abc123'
I think you would want to use \b (word boundaries):
var str = 'the first 3 letters of the alphabet are abc. not abc123';
var pat = /\b(abc)\b/g;
console.log(str.match(pat));
Live example: http://jsfiddle.net/uu5VJ/
If the former solution works for you, I would advise against using it.
That means you may have something like the following:
var strs = ['abc', 'abc1', 'abc2']
for (var i = 0; i < strs.length; i++) {
if (strs[i] == 'abc') {
//do something
}
else {
//do something else
}
}
While you could use
if (str[i].match(/^abc$/g)) {
//do something
}
It would be considerably more resource-intensive. For me, a general rule of thumb is for a simple string comparison use a conditional expression, for a more dynamic pattern use a regular expression.
More on JavaScript regexes: https://developer.mozilla.org/en/JavaScript/Guide/Regular_Expressions

"^" For the begining of the line "$" for the end of it. Eg.:
var re = /^abc$/;
Would match "abc" but not "1abc" or "abc1". You can learn more at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions

Regex to return different parts if starts with specific string

I'm trying to use a regular expression to return a value from a string if it starts like "P0000000S" but if it doesn't then return another.
For example:
I have this string
P0000000S521500500015 1TZ003B 3090942 04260
Result: 3090942
As this starts with P0000000S it should return this result: 3090942
But this one
P3417677S521500500015 1TZ003B 3090942 04260
Result: 3419677
Should return the numbers that are between the first P until the S: 3417677
After reading and investigating I came up with this Regex:
(?(?=^P0000000S)^.{29}\s(\w+)\s.{5}$|^P(\d+).{35})
Which according to this site where I tested it's working
https://regex101.com/r/aH1vG7/1
Well, I'm trying to use this on a C# APS.NET site that I'm creating but it's not working, I need to clarify that I need to do the IF-THEN-ELSE logic on the Regex because this is a validator for one of a lot of other validators and all the other ones are working.
If it's of any help I use this with Regex.Match function and then cycle the resulting groups.
Thanks.

Use two different conditions with lookarounds:
var regex = new Regex(#"(?<=P0000000S\w+\s\w+\s)\w+|(?<=P)\d+(?=S)");
You just need to filter that the result is not 0000000.

Just use two different regexen and fall through if there's no match for the first one.
static string PartImInterestedIn(string input)
{
Match match;
match = Regex.Match(input, #"(?=^P0000000S)\S+ \S+ (\S+)");
if (!match.Success)
{
match = Regex.Match(input, #"^P(\d+)S");
}
return match.Groups[1].Value;
}

How to do this Regex in C#?

I've been trying to do this for quite some time but for some reason never got it right.
There will be texts like these:
12325 NHGKF
34523 KGJ
29302 MMKSEIE
49504EFDF
The rule is there will be EXACTLY 5 digit number (no more or less) after that a 1 SPACE (or no space at all) and some text after as shown above. I would like to have a MATCH using a regex pattern and extract THE NUMBER and SPACE and THE TEXT.
Is this possible? Thank you very much!

Since from your wording you seem to need to be able to get each component part of the input text on a successful match, then here's one that'll give you named groups number, space and text so you can get them easily if the regex matches:
(?<number>\d{5})(?<space>\s?)(?<text>\w+)
On the returned Match, if Success==true then you can do:
string number = match.Groups["number"].Value;
string text = match.Groups["text"].Value;
bool hadSpace = match.Groups["space"] != null;

The expression is relatively simple:
^([0-9]{5}) ?([A-Z]+)$
That is, 5 digits, an optional space, and one or more upper-case letter. The anchors at both ends ensure that the entire input is matched.
The parentheses around the digits pattern and the letters pattern designate capturing groups one and two. Access them to get the number and the word.

string test = "12345 SOMETEXT";
string[] result = Regex.Split(test, #"(\d{5})\s*(\w+)");

You could use the Split method:
public class Program
{
static void Main()
{
var values = new[]
{
"12325 NHGKF",
"34523 KGJ",
"29302 MMKSEIE",
"49504EFDF"
};
foreach (var value in values)
{
var tokens = Regex.Split(value, #"(\d{5})\s*(\w+)");
Console.WriteLine("key: {0}, value: {1}", tokens[1], tokens[2]);
}
}
}

A probably simple regex expression

I am a complete newb when it comes to regex, and would like help to make an expression to match in the following:
{ValidFunctionName}({parameter}:"{value}")
{ValidFunctionName}({parameter}:"{value}",
{parameter}:"{value}")
{ValidFunctionName}()
Where {x} is what I want to match, {parameter} can be anything $%"$ for example and {value} must be enclosed in quotation marks.
ThisIsValid_01(a:"40")
would be "ThisIsValid_01", "a", "40"
ThisIsValid_01(a:"40", b:"ZOO")
would be "ThisIsValid_01", "a", "40", "b", "ZOO"
01_ThisIsntValid(a:"40")
wouldn't return anything
ThisIsntValid_02(a:40)
wouldn't return anything, as 40 is not enclosed in quotation marks.
ThisIsValid_02()
would return "ThisIsValid_02"
For a valid function name I came across: "[A-Za-z_][A-Za-z_0-9]*"
But I can't for the life of me figure out how to match the rest.
I've been playing around on http://regexpal.com/ to try to get valid matches to all conditions, but to no avail :(
It would be nice if you kindly explained the regex too, so I can learn :)

EDIT: This will work, uses 2 regexs. The first get the function name and everything inside it, the second extracts each pair of params and values from what's inside the function's brackets. You cannot do this with a single regex. Add some [ \t\n\r]* for whitespace.
Regex r = new Regex(#"(?<function>\w[\w\d]*?)\((?<inner>.*?)\)");
Regex inner = new Regex(#",?(?<param>.+?):""(?<value>[^""]*?)""");
string input = "_test0(a:\"lolololol\",b:\"2\") _test1(ghgasghe:\"asjkdgh\")";
List<List<string>> matches = new List<List<string>>();
MatchCollection mc = r.Matches(input);
foreach (Match match in mc)
{
var l = new List<string>();
l.Add(match.Groups["function"].Value);
foreach (Match m in inner.Matches(match.Groups["inner"].Value))
{
l.Add(m.Groups["param"].Value);
l.Add(m.Groups["value"].Value);
}
matches.Add(l);
}
(Old) Solution
(?<function>\w[\w\d]*?)\((?<param>.+?):"(?<value>[^"]*?)"\)
(Old) Explanation
Let's remove the group captures so it is easier to understand: \w[\w\d]*?\(.+?:"[^"]?"\)
\w is the word class, it is short for [a-zA-Z_]
\d is the digit class, it is short for [0-9]
\w[\w\d]*? Makes sure there is valid word character for the start of the function, and then matches zero or more further word or digit characters.
\(.+? Matches a left bracket then one or more of any characters (for the parameter)
:"[^"]*?"\) Matches a colon, then the opening quote, then zero or more of any character except quotes (for the value) then the close quote and right bracket.
Brackets (or parens, as some people call them) as escaped with the backslashes because otherwise they are capturing groups.
The (?<name> ) captures some text.
The ? after each the * and + operators makes them non-greedy, meaning that they will match the least, rather than the most, amount of text.
(Old) Use
Regex r = new Regex(#"(?<function>\w[\w\d]*?)\((?<param>.+?):""(?<value>[^""]*?)""");
string input = "_test0(aa%£$!:\"lolololol\") _test1(ghgasghe:\"asjkdgh\")";
List<string[]> matches = new List<string[]>();
if(r.IsMatch(input))
{
MatchCollection mc = r.Matches(input);
foreach (Match match in mc)
matches.Add(new[] { match.Groups["function"].Value, match.Groups["param"].Value, match.Groups["value"].Value });
}
EDIT: Now you've added an undefined number of multiple parameters, I would recommend making your own parser rather than using regexs. The above example only works with one parameter and strictly no whitespace. This will match multiple parameters with strict whitespace but will not return the parameters and values:
\w[\w\d]*?\(.+?:"[^"]*?"(,.+?:"[^"]*?")*\)
Just for fun, like above but with whitepace:
\w[\w\d]*?[ \t\r\n]*\([ \t\r\n]*.+?[ \t\r\n]*:[ \t\r\n]*"[^"]*?"([ \t\r\n]*,[ \t\r\n]*.+?[ \t\r\n]*:[ \t\r\n]*"[^"]*?")*[ \t\r\n]*\)
Capturing the text you want will be hard, because you don't know how many captures you are going to have and as such regexs are unsuited.

Someone else has already given an answer that gives you a flat list of strings, but in the interest of strong typing and proper class structure, I’m going to provide a solution that encapsulates the data properly.
First, declare two classes:
public class ParamValue // For a parameter and its value
{
public string Parameter;
public string Value;
}
public class FunctionInfo // For a whole function with all its parameters
{
public string FunctionName;
public List<ParamValue> Values;
}
Then do the matching and populate a list of FunctionInfos:
(By the way, I’ve made some slight fixes to the regexes... it will now match identifiers correctly, and it will not include the double-quotes as part of the “value” of each parameter.)
Regex r = new Regex(#"(?<function>[\p{L}_]\w*?)\((?<inner>.*?)\)");
Regex inner = new Regex(#",?(?<param>.+?):""(?<value>[^""]*?)""");
string input = "_test0(a:\"lolololol\",b:\"2\") _test1(ghgasghe:\"asjkdgh\")";
var matches = new List<FunctionInfo>();
if (r.IsMatch(input))
{
MatchCollection mc = r.Matches(input);
foreach (Match match in mc)
{
var l = new List<ParamValue>();
foreach (Match m in inner.Matches(match.Groups["inner"].Value))
l.Add(new ParamValue
{
Parameter = m.Groups["param"].Value,
Value = m.Groups["value"].Value
});
matches.Add(new FunctionInfo
{
FunctionName = match.Groups["function"].Value,
Values = l
});
}
}
Then you can access the collection nicely with identifiers like FunctionName:
foreach (var match in matches)
{
Console.WriteLine("{0}({1})", match.FunctionName,
string.Join(", ", match.Values.Select(val =>
string.Format("{0}: \"{1}\"", val.Parameter, val.Value))));
}

Try this:
^\s*(?<FunctionName>[A-Za-z][A-Za-z_0-9]*)\(((?<parameter>[^:]*):"(?<value>[^"]+)",?\s*)*\)
^\s*(?<FunctionName>[A-Za-z][A-Za-z_0-9]*) matches the function name, ^ means start of the line, so that the first character in string must match. You can keep you remove the whitespace capture if you don't need it, I just added it to make the match a little more flexible.
The next set \(((?<parameter>[^:]*):"(?<value>[^"]+)",?)*\) means capture each parameter-value pair inside the parenthesis. You have to escape the parenthesis for the function since they are symbols within the regex syntax.
The ?<> inside parenthesis are named capture groups, which when supported by a library, as they are in .NET, make grabbing the groups in the matches a little easier.

Here:
\w[\w\d]*\s*\(\s*(?:(\w[\w\d]*):("[^"]*"|\d+))*\s*\)
Visualization of that regex here.

For Problems like that I always suggest people not to "find" a single regex but to write multiple regex sharing the work.
But here is my quick shot:
(?<funcName>[A-Za-z_][A-Za-z_0-9]*)
\(
(?<ParamGroup>
(?<paramName>[^(]+?)
:
"(?<paramValue>[^"]*)"
((,\s*)|(?=\)))
)*
\)
The whitespaces are there for better readability. Remove them or set the option to ignore pattern whitespaces.

This regex passes all your test cases:
^(?<function>[A-Za-z][\w]*?)\(((?<param>[^:]*?):"(?<value>[^"]*?)",{0,1}\s*)*\)$
This works on multiple parameters and no parameters. It also handles special characters in the param name and whitespace after the comma. There may need to be some adjustments as your test cases do not cover everything you indicate in your text.
Please note that \w usually includes digits and is not appropriate as the leading character of the function name. Reference: http://www.regular-expressions.info/charclass.html#shorthand

How can I find a string after a specific string/character using regex

I am hopeless with regex (c#) so I would appreciate some help:
Basicaly I need to parse a text and I need to find the following information inside the text:
Sample text:
KeywordB:***TextToFind* the rest is not relevant but **KeywordB: Text ToFindB and then some more text.
I need to find the word(s) after a certain keyword which may end with a “:”.
[UPDATE]
Thanks Andrew and Alan: Sorry for reopening the question but there is quite an important thing missing in that regex. As I wrote in my last comment, Is it possible to have a variable (how many words to look for, depending on the keyword) as part of the regex?
Or: I could have a different regex for each keyword (will only be a hand full). But still don't know how to have the "words to look for" constant inside the regex

The basic regex is this:
var pattern = #"KeywordB:\s*(\w*)";
\s* = any number of spaces
\w* = 0 or more word characters (non-space, basically)
() = make a group, so you can extract the part that matched
var pattern = #"KeywordB:\s*(\w*)";
var test = #"KeywordB: TextToFind";
var match = Regex.Match(test, pattern);
if (match.Success) {
Console.Write("Value found = {0}", match.Groups[1]);
}
If you have more than one of these on a line, you can use this:
var test = #"KeywordB: TextToFind KeyWordF: MoreText";
var matches = Regex.Matches(test, #"(?:\s*(?<key>\w*):\s?(?<value>\w*))");
foreach (Match f in matches ) {
Console.WriteLine("Keyword '{0}' = '{1}'", f.Groups["key"], f.Groups["value"]);
}
Also, check out the regex designer here: http://www.radsoftware.com.au/. It is free, and I use it constantly. It works great to prototype expressions. You need to rearrange the UI for basic work, but after that it's easy.
(fyi) The "#" before strings means that \ no longer means something special, so you can type #"c:\fun.txt" instead of "c:\fun.txt"

Let me know if I should delete the old post, but perhaps someone wants to read it.
The way to do a "words to look for" inside the regex is like this:
regex = #"(Key1|Key2|Key3|LastName|FirstName|Etc):"
What you are doing probably isn't worth the effort in a regex, though it can probably be done the way you want (still not 100% clear on requirements, though). It involves looking ahead to the next match, and stopping at that point.
Here is a re-write as a regex + regular functional code that should do the trick. It doesn't care about spaces, so if you ask for "Key2" like below, it will separate it from the value.
string[] keys = {"Key1", "Key2", "Key3"};
string source = "Key1:Value1Key2: ValueAnd A: To Test Key3: Something";
FindKeys(keys, source);
private void FindKeys(IEnumerable<string> keywords, string source) {
var found = new Dictionary<string, string>(10);
var keys = string.Join("|", keywords.ToArray());
var matches = Regex.Matches(source, #"(?<key>" + keys + "):",
RegexOptions.IgnoreCase);
foreach (Match m in matches) {
var key = m.Groups["key"].ToString();
var start = m.Index + m.Length;
var nx = m.NextMatch();
var end = (nx.Success ? nx.Index : source.Length);
found.Add(key, source.Substring(start, end - start));
}
foreach (var n in found) {
Console.WriteLine("Key={0}, Value={1}", n.Key, n.Value);
}
}
And the output from this is:
Key=Key1, Value=Value1
Key=Key2, Value= ValueAnd A: To Test
Key=Key3, Value= Something

/KeywordB\: (\w)/
This matches any word that comes after your keyword. As you didn´t mentioned any terminator, I assumed that you wanted only the word next to the keyword.