It is common way to replace a pattern match with string, but I need to replace all sub-strings which match pattern from text to be matched as another pattern match, is it possible?
For example, is it possible to replace all matches to
[0-9]{2}'[0-9]{2} which represent all strings like 99'99 or 85'55
To this [0-9]{2}.[0-9]{2} which represent all strings like 99.99 or 85.55
Is it possible? How to do this kind of replacements?
or I have to handle it manually through matches in for each loop?
Use the Regex.Replace() instance function along with Regex capture groups like this:
var regex = new Regex("([0-9]{2})'([0-9]{2})");
string result = regex.Replace(input, "$1.$2");
More details about capture groups can be found here.
Also, check out this answer. It shows how to use 'named' groups which might help in future.
So as I understand you, you have something like 99'99 or 85'55 and want this to be replaced by 99.99 or 85.55?
What you might look for are capture groups, i.e. find for a matching, catch this matching and put this to the result.
the RegEx here would be s/([0-9]{2})'([0-9]{2})/$1.$2/g
Explanation:
([0-9]{2}) the brackets declare the caption group. It means, whatever is captured in it, will be stored to a variable.
These Variables are $1 and $2, because there were two capture groups.
When building the replacement string, just insert those variables and put the dot between them.
Related
I'm looking to write a regex (C#) that will match words that aren't surrounded by quotes. An example input string would be:
dbo.test line_length "quoted words" notquoted
And this needs to match
dbo.test
line_length
nonquoted
So 3 separate matches and "quoted words" is not matched. The quoted phrase could be anywhere in the input...beginning, middle, end, etc.
I haven't been able to come up with a regex that matches words not in quotes where there could be a space in the quotes...I've been able to match something like: hello "world" and only get hello.
Is there a way to write the regex I'm trying to?
There are two ways to tackle this, depending on what you want to do with the output.
First, match (but don't capture) any text within quotation marks. (This is specifically matching the stuff that you DON'T want.)
Using the | pipe, use capture groups to select everything that you DO want to keep.
Example:
".*?"|(\b\S+\b)
You can see an example of that here.
The other option, using look-arounds, is to specifically look backward from the beginning of the words to ensure that the " doesn't appear there:
(?<!")(\b\S+\b)(?!")
You can see that here.
This may have a problem when you start using multiple words, but this should get you on the right track, and you can indicate whether one of these methods works better for you than the other.
I'm looking to write a regex (C#) that will match words that aren't surrounded by quotes. An example input string would be:
dbo.test line_length "quoted words" notquoted
And this needs to match
dbo.test
line_length
nonquoted
So 3 separate matches and "quoted words" is not matched. The quoted phrase could be anywhere in the input...beginning, middle, end, etc.
I haven't been able to come up with a regex that matches words not in quotes where there could be a space in the quotes...I've been able to match something like: hello "world" and only get hello.
Is there a way to write the regex I'm trying to?
There are two ways to tackle this, depending on what you want to do with the output.
First, match (but don't capture) any text within quotation marks. (This is specifically matching the stuff that you DON'T want.)
Using the | pipe, use capture groups to select everything that you DO want to keep.
Example:
".*?"|(\b\S+\b)
You can see an example of that here.
The other option, using look-arounds, is to specifically look backward from the beginning of the words to ensure that the " doesn't appear there:
(?<!")(\b\S+\b)(?!")
You can see that here.
This may have a problem when you start using multiple words, but this should get you on the right track, and you can indicate whether one of these methods works better for you than the other.
I need some help on a problem.
In fact I search to check for an image type by the hexadecimal code.
string JpgHex = "FF-D8-FF-E0-xx-xx-4A-46-49-46-00";
Then I have a condition on
string.StartsWith(pngHex).
The problem is that the "x" characters presents in my "JpgHex" string can be whatever I want.
I think I need a regex to check that but I don't know how!!
Thanks a lot!
I'm not quite clear what exactly you want to do, but the dot '.' character represents any character in Regex.
So the regex "^FF-D8-FF-E0-..-..-4A-46-49-46-00" will probably do the trick. '^' = Start of input.
If you want to allow only hex chars you can use "^FF-D8-FF-E0-[0-9A-F]{2}-[0-9A-F]{2}-4A-46-49-46-00".
Like I said, I'd need a better idea of what pattern you need to match.
Here are some examples:
Regex rgx =
new Regex(#"^FF-D8-FF-E0-[a-zA-Z0-9]{2}-[a-zA-Z0-9]{2}-4A-46-49-46-00$");
rgx.IsMatch(pngHex); // is match will return a bool.
I use [a-zA-Z0-9]{2} to denote two instances of a character, caps or small or a number. So the above regex would match :
FF-D8-FF-E0-aa-zZ-4A-46-49-46-00
FF-D8-FF-E0-11-22-4A-46-49-46-00
.. etc
Based on your need change the regex accordingly so for capitals and numbers only you change to [A-Z0-9]. The {2} denotes two occurrences.
The ^ denotes the string should start with FF and $ means the string should end with 00.
Lets say you wanted to only match two numbers, so you would use \d{2}, the whole thing would look like this:
Regex rgx = new Regex(#"^FF-D8-FF-E0-\d{2}-\d{2}-4A-46-49-46-00$");
rgx.IsMatch(pngHex);
How do I know of these magical characters? Simple, there are docs everywhere. See this MSDN page for some basic regex patterns. This page shows some quantifiers, those are things like match one or more or match only one.
Cheat-sheets also come in handy.
A regex would help you; you can use the following tool to help you test and learn: -
http://derekslager.com/blog/posts/2007/09/a-better-dotnet-regular-expression-tester.ashx
I recommend you have a play because then you'll learn!
To simply match any character in place of the x, the following should work: -
"^FF-D8-FF-E0-..-..-4A-46-49-46-00$"
In C#, it would be something like this: -
var test = "FF-D8-FF-E0-AB-CD-4A-46-49-46-00";
var foo = new Regex("^FF-D8-FF-E0-..-..-4A-46-49-46-00$");
if (foo.IsMatch(test))
{
// Do magic
}
You will need to read up on regular expressions to understand some of the characters that may not look familiar, i.e. ^ and $. See http://www.regular-expressions.info/
I would like to be able to match and then extract all substrings in the following string using regex in c#:
"2012-05-15 00:49:02 192.168.100.10 POST /Microsoft-Server-ActiveSync/default.eas User=nikced&DeviceId=ApplDNWGRKZQDTC0&DeviceType=iPhone&Cmd=Ping&Log=V121_Sst8_LdapC0_LdapL0_RpcC31_RpcL50_Hb3540_Erq1_Pk1728465481_S2_ 443 redcloud\nikced 94.234.170.42 Apple-iPhone4C1/902.179 200 0 64 3140491"
Since it's a logfile it the regex should be able to handle any line that is of a similar type.
In this case, the preferred output to a collection should be:
2012-05-15
00:49:02
192.168.100.10
/Microsoft-Server-ActiveSync/default.eas
User=nikced&DeviceId=ApplDNWGRKZQDTC0&DeviceType=iPhone&Cmd=Ping&Log=V121_Sst8_LdapC0_LdapL0_RpcC31_RpcL50_Hb3540_Erq1_Pk1728465481_S2_
443
redcloud\nikced
94.234.170.42
Apple-iPhone4C1/902.179
200
0
64
3140491
Appreciate any answer using C#, .net and Regex to extract the above substrings into a collection (MatchCollection preferred). All log lines follows the same format and pattern.
Incredibly complex regex incoming:
logFile.Split(' ');
This will give you an array that you can iterate through to retrieve all of the "lines" which are separated by a space
string[] lines = log.Split(' ');
You don't need to use a Regex. You can simply use String.Split Method, and specify space as separator:
string [] substrings = line.Split(new Char [] {' '});
If you need to identify the kind of each part, then you should specify what you need to find, and a regex can be created for it.
Anyway, if you really want to use a Regex, do this:
Regex re = new Regex (#"(?:(?<s>[^ ]+)(?: |$))*");
This will give you all the captures in the "s" group, when you call the Match method.
As the OP pointed out in a comment that the separator can be anything appart from a single space, then the possible separators should be included in the (?: |$) and the [^ ] parts of the expression. I.e. if space as well as tab are possible separators, replace that part with (?: |\t|$) and [^ \t]. If you need to accept more than one of those characters as separators, add a + after the () group:
(?:(?<s>[^ \t]+)(?: |\t|$)+)*
The fastest and most obvious way is to use String.Split:
string[] substrings = result = line->Split( nullptr, StringSplitOptions::RemoveEmptyEntries );
But if you insist on a MatchCollection then this will do what you want
MatchCollection ^ substrings = Regex.Matches(line, "\\S+")
Really, you just need to break this down into the parts.
First, the date. Will it always be in YYYY-MM-DD format? Could it be possible that it will be different based on region/culture settings?
(?<LogDate>dddd-dd-dd)
Next, you have the time. Same thing:
(?<LogTime>dd:dd:dd)
Next, I'm assuming this is the web method that was actually called? Not entirely sure, since you haven't really explained how the data is laid out. However, I'm assuming it's either going to be either POST or GET, so that's what we're going to do next...
(?<LogMethod>POST|GET)
Just do this for every part of the log line you're interested in, and you'll be set. IE:
(?<LogDate>dddd-dd-dd) (?<LogTime>dd:dd:dd) (?<LogMethod>POST|GET)...
If you want to anchor to the start/end of the line, be sure to use ^ and $ respectively. When you get the Matches, you can get the values from each group by indexing the Groups property with the named group (such as match.Groups["LogMethod"].Value). Good luck!
i'm having a hard time finding a solution to this and am pretty sure that regex supports it. i just can't recall the name of the concept in the world of regex.
i need to search and replace a string for a specific pattern but the patterns can be different and the replacement needs to "remember" what it's replacing.
For example, say i have an arbitrary string: 134kshflskj9809hkj
and i want to surround the numbers with parentheses,
so the result would be: (134)kshflskj(9809)hkj
Finding numbers is simple enough, but how to surround them?
Can anyone provide a sample or point me in the right direction?
In some various langauges:
// C#:
string result = Regex.Replace(input, #"(\d+)", "($1)");
// JavaScript:
thestring.replace(/(\d+)/g, '($1)');
// Perl:
s/(\d+)/($1)/g;
// PHP:
$result = preg_replace("/(\d+)/", '($1)', $input);
The parentheses around (\d+) make it a "group" specifically the first (and only in this case) group which can be backreferenced in the replacement string. The g flag is required in some implementations to make it match multiple times in a single string). The replacement string is fairly similar although some languages will use \1 instead of $1 and some will allow both.
Most regex replacement functions allow you to reference capture groups specified in the regex (a.k.a. backreferences), when defining your replacement string. For instance, using preg_replace() from PHP:
$var = "134kshflskj9809hkj";
$result = preg_replace('/(\d+)/', '(\1)', $var);
// $result now equals "(134)kshflskj(9809)hkj"
where \1 means "the first capture group in the regex".
Another somewhat generic solution is this:
search : /([\d]+)([^\d]*)/g
replace: ($1)$2
([\d]+): match a set of one or more digits and retain them in a group
([^\d]*): match a set of non-digits, and retain them as well. \D could work here, too.
g: indicate this is a global expression, to work multiple times on the input.
($1): in the replace block, parens have no special meaning, so output the first group, surrounding it with parens.
$2: output the second group
I used a pretty good online regex tool to test out my expression. The next step would be to apply it to the language that you are using, as each has its own implemention nuance.
Backreferences (grouping) are not necessary if you're just looking to search for numbers and replace with the found regex surrounded by parens. It is simpler to use the whole regex match in the replacement string.
e.g for perl
$text =~ s/\d+/($&)/g;
This searches for 1 or more digits and replaces with parens surrounding the match (specified by $&), with trailing g to find and replace all occurrences.
see http://www.regular-expressions.info/refreplace.html for the correct syntax for your regex language.
Depending on your language, you're looking to match groups.
So typically you'll make a pattern in the form of
([0-9]{1,})|([a-zA-Z]{1,})
Then, you'll iterate over the resulting groups in (specific to your language).