How to rewrite the [a-zA-Z0-9!$* \t\r\n] pattern to match hyphen along with the existing characters ?
The hyphen is usually a normal character in regular expressions. Only if it’s in a character class and between two other characters does it take a special meaning.
Thus:
[-] matches a hyphen.
[abc-] matches a, b, c or a hyphen.
[-abc] matches a, b, c or a hyphen.
[ab-d] matches a, b, c or d (only here the hyphen denotes a character range).
Escape the hyphen.
[a-zA-Z0-9!$* \t\r\n\-]
UPDATE:
Never mind this answer - you can add the hyphen to the group but you don't have to escape it. See Konrad Rudolph's answer instead which does a much better job of answering and explains why.
It’s less confusing to always use an escaped hyphen, so that it doesn't have to be positionally dependent. That’s a \- inside the bracketed character class.
But there’s something else to consider. Some of those enumerated characters should possibly be written differently. In some circumstances, they definitely should.
This comparison of regex flavors says that C♯ can use some of the simpler Unicode properties. If you’re dealing with Unicode, you should probably use the general category \p{L} for all possible letters, and maybe \p{Nd} for decimal numbers. Also, if you want to accomodate all that dash punctuation, not just HYPHEN-MINUS, you should use the \p{Pd} property. You might also want to write that sequence of whitespace characters simply as \s, assuming that’s not too general for you.
All together, that works out to apattern of [\p{L}\p{Nd}\p{Pd}!$*] to match any one character from that set.
I’d likely use that anyway, even if I didn’t plan on dealing with the full Unicode set, because it’s a good habit to get into, and because these things often grow beyond their original parameters. Now when you lift it to use in other code, it will still work correctly. If you hard‐code all the characters, it won’t.
[-a-z0-9]+,[a-z0-9-]+,[a-z-0-9]+ and also [a-z-0-9]+ all are same.The hyphen between two ranges considered as a symbol.And also [a-z0-9-+()]+ this regex allow hyphen.
use "\p{Pd}" without quotes to match any type of hyphen. The '-' character is just one type of hyphen which also happens to be a special character in Regex.
Is this what you are after?
MatchCollection matches = Regex.Matches(mystring, "-");
Related
I am trying to develop a regular expression to match the following equations:
(Price+10%+100+200)
(Price+20%+200)
(Price+30%)
(Price+100)
(Price-10%-100-200)
(Price-20%-200)
(Price-30%)
(Price-100)
My regex so far is...
/([(])+([P])+([r])+([i])+([c])+([e])+([+]|[-]){1}([\d])+([+]|[-])?([\d])+([%])?([)])/g
..., but it only matches the following equations:
(Price+100+10%)
(Price+100+100)
(Price+200)
(Price-100-10%)
(Price-100-100)
(Price-200)
Can someone help me understand how to make my pattern match the full set of equations provided?
Note: Parentheses and 'Price' are musts in the equations that the pattern must match.
Try this, which matches all the input strings provided in the question:
/\(Price([+-]\d+%?){1,3}\)/g
You can test it in a regex fiddle.
Things to note:
Only use parentheses where you want to group. Parentheses around single-possibility, fixed-quantity matches (e.g. ([P]) provide no value.
Use character classes (opened with [ and closed with ]) for multiple characters that can match at a position in the pattern (e.g. [+-]). Single-possibility character classes (e.g. [P]) similarly provide no value.
Yes, character classes (generally) implicitly escape regex special characters within them (e.g. ( in [(] vs. equivalent \( outside a character class), but to just escape regex special characters (i.e. to match them literally), you are better off not using a character class and just escaping them (e.g. \() – unless multiple characters should match at a position in the pattern (per the previous point to note).
The quantifier {1} is (almost) always useless: drop it.
The quantifier + means "one or more" as you probably know. However, in a series of cases where you used it (i.e. ([(])+([P])+([r])+([i])+([c])+([e])+), it would match many values that I doubt you expect (e.g. ((((((PPPrriiiicccceeeeee): basically, don't overuse it. Stop to consider whether you really want to match one or more of the character (class) or group to which + applies in the pattern.
To match a literal string without any regex special characters like Price, just use the literal string at the appropriate position in the pattern – e.g. Price in \(Price.
/\(Price[+-](\d)+(%)?([+-]\d+%?)?([+-]\d+%?)?\)/g
works on http://www.regexr.com/
/^[(Price]+\d+\d+([%]|[)])&/i
try at your own risk!
I need a JS regular expression which should allow only the word having alphanumeric, dot and hyphen.
Let me know this is correct.
var regex = /^[a-zA-Z_0-9/.-]+$/;
Almost. That will also allow underscores and slashes. Remove those from your range:
var regex = /^[a-zA-Z0-9.-]+$/;
This will also not match the empty string. That may be what you want, but it also may not be what you want. If it's not what you want, change + to *.
The first simplifications I'd make are to use the "word character" shorthand '\w', which is about the same as 'a-zA-Z', but shorter, and automagically stays correct when you move to other languages that include some accented alphabetic characters, and the "digit character" shorthand '\d'.
Also, although dot is special in most places in regular expressions, it's not special inside square brackets, and shouldn't be quoted there. (Besides, the single character quote character is back-slash, not forward-slash. That forward-slash of yours inside the brackets is the same character that begins and ends the RE, and so is likely to prematurely terminate the RE and so cause a parse error!) Since we're completely throwing it away, it no longer matters whether it should be forward-slash or back-slash, quoted or bare.
And as you've noticed, hyphen has a special meaning of "range" inside brackets (ex: a-z), so if you want a literal hyphen you have to do something a little different. By convention that something is to put the literal hyphen first inside the brackets.
So my result would be var regex = /^[-.\w\d]+$/;
(As you've probably noticed, there's almost always more than one way to express a regular expression so it works, and RE weenies spend as much time on a) economy of expression and b) run-time performance as they do on getting it "correct". In other words, you can ignore much of what I've just said, as it doesn't really matter to you. I think all that really matters is a) getting rid of that extraneous forward-slash and b) moving the literal hyphen to be the very first character inside the square brackets.)
(Another thought: very frequently when accepting alphabetic characters and hyphens, underscore is acceptable too ...so did you really mean to have that underscore after all?)
(Yet another thought: sometimes the very first character of an identifier must be an alpha, in which case what you probably want is var regex = /^\w[-.\w\d]*$/; You may want a different rule for the very first character in any case, as the naive recipe above would allow "-" and "." as legitimate words of length one.)
I would like to construct a regular expression that matches any letter (including accented and Greek), number, hyphens and spaces with a total allowed characters length between 3 and 50.
This is what I made:
[- a-zA-Z0-9çæœáééíóúžàèìòùäëïöüÿâêîôûãñõåøαβγδεζηθικλμνξοπρστυφχψωÇÆŒÁÉÍÓÚŽÀÈÌÒÙÄËÏÖÜŸÂÊÎÔÛÃÑÕÅØΑΒΓΔΕΖΗΘΙΚΛΜΝΞΟΠΡΣΤΥΦΧΨΩ]{3,50}
Now I wan't to adjust the expression so that it can't start with a hyphen or space. It will be used to validate a username.
I thought about using a negative lookbehind but these are the limitations:
JavaScript doesn't support a lookbehind.
The alternatives for a lookbehind aren't really applicable since they all depend on other JavaScript functions and I am bound to using the match function.
I hope there are any regular expression heroes here since it doesn't look simple.
I replaced your long character class with a-z for readability:
[a-z][- a-z]{2,49}
You could also match with your current regex and then make sure that the string does not match ^[ -] in another match.
For text validation for chars I am using like [a-zA-z] and for numbers like [0-9] ..if I need to add special symbols I am adding slash like [a-zA-z/-/].
While including lot of symbols its getting difficult and my javascript is getting extremely big. Is there an easy way to do it ?
Regards
A.Collins
You can take a look at this cheat sheet. for instance, [0-9] can be reduced to \d.
For the general case of "a lot of characters" — no.
\w for alphanumerics and underscores
\d for digits
\s for whitespace
You can mix them, resulting in stuff like, for example, [\d.] (for matching numbers & dots).
In a character class, x-y means "all characters between x and y". If you just have one additional character, in your case / then you don't need to use the x-y format, you can just drop the character in:
[a-zA-z/]
That's not the correct way to escape characters. \ is the correct escape character to be used:
[a-zA-Z\/]
You can use character classes, [a-zA-Z0-9] can be replaced by [\w]. The only characters that needs to be escaped are \ and -. ^ should be escaped too when it's the first character in the character class.
Two quick questions:
What would be a RegEx string for three letters and two numbers with space before and after them (i.e. " LET 12 ")?
Would you happen to know any good RegEx resources/tools?
For a good resource, try this website and the program RegexBuddy. You may even be able to figure out the answer to your question yourself using these sites.
To start you off you want something like this:
/^[a-zA-Z]{3}\s+[0-9]{2}$/
But the exact details depend on your requirements. It's probably a better idea that you learn how to use regular expressions yourself and then write the regular expression instead of just copying the answers here. The small details make a big difference. Examples:
What is a "letter"? Just A-Z or also foreign letters? What about lower case?
What is a "number"? Just 0-9 or also foreign numerals? Only integers? Only positive integers? Can there be leading zeros?
Should there be a single space between the letters and numbers? Or any amount of any whitespace? Even none?
Do you want to search for this string in a larger text? Or match a line exactly?
etc..
The answers to these questions will change the regular expression. It would be much faster for you in the long run to learn how to create the regular expression than to completely specify your requirements and wait for other people to reply.
I forgot to mention that there will be a space before and after. How do I include that?
Again you need to consider the questions:
Do you mean just one space or any amount of spaces? Possibly not always a space but only sometimes?
Do you mean literally a space character or any whitespace characters?
My guess is:
/^\s+[a-zA-Z]{3}\s+[0-9]{2}\s+$/
/[a-z]{3} [0-9]{2}/i will match 3 letters followed by a whitespace character, and then 2 numbers. [a-z] is a character class containing the letters a through z, and the {3} means that you want exactly 3 members of that class. The space character matches a literal space (alternately, you could use \s, which is a "shorthand" character class that matches any whitespace character). The i at the end is a pattern modifier specifying that your pattern is case-insenstive.
If you want the entire string to only be that, you need to anchor it with ^ and $:
/^[a-z]{3} [0-9]{2}$/i
Regular expression resources:
http://www.regular-expressions.info - great tutorial with a lot of information
http://rexv.org/ - online regular expression tester that supports a variety of engines.
^([A-Za-z]{3}) ([0-9]{2})$ assuming one space between the letters/numbers, as in your example. This will capture the letters and numbers separately.
I use http://gskinner.com/RegExr/ - it allows you to build a regex and test it with your own text.
As you can probably tell from the wide variety of answers, RegEx is a complex subject with a wide variety of opinions and preferences, and often more than one way of doing things. Here's my preferred solution.
^[a-zA-Z]{3}\s*\d{2}$
I used [a-zA-Z] instead of \w because \w sometimes includes underscores.
The \s* is to allow zero or more spaces.
I try to use character classes wherever possible, which is why I went with \d.
\w{3}\s{1}\d{2}
And I like this site.
EDIT:[a-zA-Z]{3}\s{1}\d{2} - The \w supports numeric characters too.
try this regularexpression
[^"\r\n]{3,}