What I am trying to do is fairly simple, although I am running into difficulty. I have a string that is a url, it will have the format http://www.somedomain.com?id=someid what I want to retrive is the someid part. I figure I can use a regular expression but I'm not very good with them, this is what I tried:
Match match = Regex.Match(theString, #"*.?id=(/d.)");
I get a regex exception saying there was an error parsing the regex. The way I am reading this is "any number of characters" then the literal "?id=" followed "by any number of digits". I put the digits in a group so I could pull them out. I'm not sure what is wrong with this. If anyone could tell me what I'm doing wrong I would appreciated it, thanks!
No need for Regex. Just use built-in utilities.
string query = new Uri("http://www.somedomain.com?id=someid").Query;
var dict = HttpUtility.ParseQueryString(query);
var value = dict["id"]
You've got a couple of errors in your regex. Try this:
Match match = Regex.Match(theString, #".*\?id=(\d+)");
Specifically, I:
changed *. to .* (dot matches all non-newline chars and * means zero or more of the preceding)
added a an escape sequence before the ? because the question mark is a special charcter in regular expressions. It means zero or one of the preceding.
changed /d. to \d* (you had the slash going the wrong way and you used dot, which was explained above, instead of * which was also explained above)
Try
var match = RegEx.Match(theString, #".*\?id=(\d+)");
The error is probably due to preceding *. The * character in regex matches zero or more occurrences of previous character; so it cannot be the first character.
Probably a typo, but shortcut for digit is \d, not /d
. matches any character, you need to match one or more digits - so use a +
? is a special character, so it needs to be escaped.
So it becomes:
Match match = Regex.Match(theString, #".*\?id=(\d+)");
That being said, regex is not the best tool for this; use a proper query string parser or things will eventually become difficult to manage.
Related
I've been trying to figure this out, but I don't think I understand Regex well enough to get to where I need to.
I have string that resemble these:
filename.txt(1)attribute, 2)attribute(s), more!)
otherfile.txt(abc, def)
Basically, a string that always starts with a filename, then has some text between parentheses. And I'm trying to extract that part which is between the main parentheses, but the text that's there can contain absolutely anything, even some more parentheses (it often does.)
Originally, there was a 'hacky' expression made like this:
/\(([^#]+)\)\g
And it worked, until we ran into a case where the input string contained a # and we were stuck. Obviously...
I can't change the way the strings are generated, it's always a filename, then some parentheses and something of unknown length and content inside.
I'm hoping for a simple Regex expression, since I need this to work in both C# and in Perl -- is such a thing possible? Or does this require something more complex, like its own parsing method?
You can change exception for # symbol in your regex to regex matches any characters and add quantifier that matches from 0 to infinity symbols. And also simplify your regex by deleting group construction:
\(.*\)
Here is the explanation for the regular expression:
Symbol \( matches the character ( literally.
.* matches any character (except for line terminators)
* quantifier matches between zero and unlimited times, as many times
as possible, giving back as needed (greedy)
\) matches the character ) literally.
You can use regex101 to compose and debug your regular expressions.
Regex seems overkill to me in this case. Can be more reliably achieved using string manipulation methods.
int first = str.IndexOf("(");
int last = str.LastIndexOf(")");
if (first != -1 && last != -1)
{
string subString = str.Substring(first + 1, last - first - 1);
}
I've never used Perl, but I'll venture a guess that it has equivalent methods.
I'm trying to learn regex, but still have no clue. I have this line of code, which successfully seperates the placeholder 'FirstWord' by the '{' delimiter from all following text:
var regexp = new Regex(#"(?<FirstWord>.*?)\{(?<TextBetweenCurlyBrackets>.*?)\}");
Which reads this string with no problem:
Greetings{Hello World}
What I want to do is to replace the '{' with a character chain like for instance '/>>'
so I tried this:
var regexp = new Regex(#"(?<FirstWord>.*?)\/>>(?<OtherText>.*?)\");
I removed the last bracket and replaced the first one with '/>>' But it throws an ArgumentException. How would the correct character combination look like?
/ does not need to be escaped, unless you use it as the pattern-delimiter.:
#"(?<FirstWord>.*?)/>>(?<OtherText>.*?)\"
Also your last \ will basically escape the " which should end the String (c#-wise: remove it):
#"(?<FirstWord>.*?)/>>(?<OtherText>.*?)"
And since you want most likely fetch until the END of the String (.*? will fetch as less characters as required to satisfy the expression), you should use the $ at the end or use any other sort of delimiter (whitspace, linebreak, etc...).
#"(?<FirstWord>.*?)/>>(?<OtherText>.*?)$"
Example:
(.*?)/>>(.*?)$
Debuggex Demo
Removing the trailing $ will fetch the empty string for the second match group, because "" is the shortest string possible satisfying the expression .*?
(.*?)/>>(.*?)$ on This/>>Test One will match This and Test One
(.*?)/>>(.*?)\s on This/>>Test One will match This and Test
(.*?)/>>(.*?) on This/>>Test One will match This and ""
Note: I'm saying "" is the shortest string possible satisfying the expression .?* on purpose! A frequent Misstake is to interpret .*?a as "everything until a":
Regex is greedy by default!
Searching for the expressiong (.*?)a$ on "caba" will NOT fail to match - it will return cab!, because cab followed by a is satisfying the expression AND cab is the shortest string possible for any match.
One might also expect b to be matched - but regex is working from left to right, hence aborting once it found cab - even if b would be shorter.
I have the following string:
"121 fd412 4151 3213, 421, 423 41241 fdsfsd"
And I need to get 3213 and 421 - because they both have space in front of them, and a coma behind.
The result will be set inside the string array...How can I do that?
"\\d+" catches every integer.
"\s\\d+(,)" throws some memory errors.
EDIT.
space to the left (<-) of the number, coma to the right (->)
EDIT 2.
string mainString = "Tests run: 5816, 8346, 28364 iansufbiausbfbabsbo3 4";
MatchCollection c = Regex.Matches(a, #"\d+(?=\,)");
var myList = new List<String>();
foreach(Match match in c)
{
myList.Add(match.Value);
}
Console.Write(myList[1]);
Console.ReadKey();
Your regex syntax is incorrect for wanting to match both digits, if you want them as separate results, you could do:
#"\s(\d+),\s(\d+)\s"
Live Demo
Edit
#"\s(\d+),"
Live Demo
\s\\d+(,):
\s is not properly escaped, should be \\s, same as for \\d
\\d matches single digit, you need \\d+ - one or more consecutive digits
(,) captures comma, do you really need this? seems like you need to capture a number, so \\s(\\d+),
you said "because they both have space behind them, and a coma in front", so probably ,\\s(\\d+)
How about this expression :
" \d+," // expression without the quotes
it should find what you need.
How to work with regular expression can you check on the MSDN
Hope it helps
Another solution
\s(\d+), // or maybe you'll need a double slash \\
Output:
3213
421
Demo
I think you mean you're looking for something like ,<space><digit> not ,<digit><space>
If so, try this:
, (\d+) //you might need to add another backslash as the others have noted
Well, based on your new edit
\s(\d+),
Test it here
It's all you need, only the numbers
\d+(?=\,)
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
In C#, how would I capture the integer value in the URL like:
/someBlah/a/3434/b/232/999.aspx
I need to get the 999 value from the above url.
The url HAS to have the /someBlah/ in it.
All other values like a/3434/b/232/ can be any character/number.
Do I have escape for the '/' ?
Try the following
var match = Regex.Match(url,"^http://.*someblah.*\/(\w+).aspx$");
if ( match.Success ) {
string name = match.Groups[1].Value;
}
You didn't specify what names could appear in front of the ASPX file. I took the simple approach of using the \w regex character which matches letters and digits. You can modify it as necessary to include other items.
You are effectively getting the file name without an extension.
Although you specifically asked for a regular expression, unless you are in a scenario where you really need to use one, I'd recommend that you use System.IO.Path.GetFileNameWithoutExtension:
Path.GetFileNameWithoutExtension(Context.Request.FilePath)
^(?:.+/)*(?:.+)?/someBlah/(?:.+/)*(.+)\.aspx$
This is a bit exhaustive, but it can handle scenarios where /someBlah/ does not have to be at the beginning of the string.
The ?: operator implies a non-capturing group, which may or may not be supported by your RegEx flavor.
Regex regex = new Regex("^http://.*someBlah.*/(\\d+).aspx$");
Match match = regex.Match(url);
int result;
if (match.Success)
{
int.TryParse(match.Groups[1].Value, out result);
}
Using \d rather than \w ensures that you only match digits, and unless the ignore case flag is set the capitalisation of someBlah must be correct.