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I am trying to check patterns in a string using regex. My requirements are

  1. The string should always start with % or (
  2. Immediately After % there should be a number and vice versa any number should be preceded by % always
  3. the string can only contain following characters and word % ( ) and or numeric value

Valid string (%1 and %2 or %3)

Invalid %%1

I tried the following 

regex ^[%(]+[%0-9]+[(]

Please help

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  • 1
    Looks like whitespace characters are OK too, right? Commented Dec 5, 2013 at 14:52
  • Yes whitespace characters are ok Commented Dec 5, 2013 at 14:53
  • Try regex ^[%(]+[%0-9\s]+[)] Commented Dec 5, 2013 at 14:55

4 Answers 4

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This should do it:

^(?:\(|%[0-9]+)(?:\s+|%[0-9]+|and|or|\(|\))*$

Starts with an opening bracket or a percent then a series of numbers, then goes on to allow spaces or a percent followed by a series of numbers any number of times. If you give a more specific example of what you are trying to match I can be more specific

enter image description here

This does not force matching brackets. You need a recursive js function for that

EDIT

Alright, here is a more specific function to account for spacing and numbers around seperators

^(?:\(|%[0-9])(?:\sand\s|\sor\s|\(+)(?:(?:%[0-9]|\)+)(?:\s(?:and|or)\s(?:%[0-9]|(?:\(\s?)+))?)*\s?\)*$

This will match something like this: %3 and %4 or ( %2 or %3 ) but fails when you try it on: %3 and %4or ( %2 or %3 ) note the missing space between the %4 and the or

Again, brackets dont need to be closed so it matches: %3 and %4 or ( %2 or %3 and it also matches: %3 and %4 or ( %2 or %3 ))))

it can deal with immediately nested brackets like this: %3 and %4 or ((%2 or %3) and %9 )

Im sure I have missed cases, let me know what issues your run into

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7 Comments

Thanks, this works perfectly. Is it possible to explain the regex?
Of course. it has two parts each surrounded by (?: ). The ?: means the parens will not capture, it makes the regex a little bit faster and is useful if all you need to do is check if the regex matches not pull what it matches out of a string. inside the first brackets is (|%[-9]+. That matches either an opening bracket or a percent followed by one or more numbers. The second portion \s+|%[0-9]+|and|or|(|) matches one or more spaces or a percent followed by one or more digits or 'and' or 'or' or either bracket 0 or more times. Let me know if you want a specific explanation of something
Thanks a lot wolffer-east
Looking at Theox's answer below I forgot that you can combine the symbols into one or which would make the regex a bit smaller. Changing that out would give you (?:[\s()]+|%[0-9]+|and|or)* for the second portion of the regex
@Rakesh KR, how did you generate that image?
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I would remove the white space from the string first just to make the regex easier.

This doesn't match exactly what you described, but matches what I think you're trying to do based on your example:

\(?%\d+\)?((and|or)\(?%\d+\)?)*

Note that it does not guarantee that the parentheses are all matched.

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Here's a solution :

^(%\d|\()(%\d|and|or|[\s()])*$

This will match strings beginning with "%N", followed by any combination of "and", "or", whitespaces, ( ), and % followed by a number.

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3 Comments

Good call on combining the symbols. I forgot that for a second there. You are only missing the option to start the string with an opening paren
@wolffer-east : Indeed, i changed that. I also saw that my regex match strings like "%1 andandandandandorororor" which is probably unwanted. I'll edit my post when I find how to fix this.
yeah, we would have to split out the %\d (or in my case %[0-9]) from the rest. Not sure if whitespace is required or not
0

try this, perhaps can help :

^[%][0-9]+|^[(][%][0-9]+[)]

http://RegExr.com?37h10

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