Question

My regex skills are not very good and recently a new data element has thrown my parser into a loop

Take the following string

“+USER=Bob Smith-GROUP=Admin+FUNCTION=Read/FUNCTION=Write”

Previously I had the following for my regex : [+\\-/]

Which would turn the result into

USER=Bob Smith
GROUP=Admin
FUNCTION=Read
FUNCTION=Write
FUNCTION=Read

But now I have values with dashes in them which is causing bad output

New string looks like “+USER=Bob Smith-GROUP=Admin+FUNCTION=Read/FUNCTION=Write/FUNCTION=Read-Write”

Which gives me the following result , and breaks the key = value structure.

USER=Bob Smith
GROUP=Admin
FUNCTION=Read
FUNCTION=Write
FUNCTION=Read
Write

Can someone help me formulate a valid regex for handling this or point me to some key / value examples. Basically I need to be able to handle + – / signs in order to get combinations.

Answer 1

You didn’t specify what regex engine you’re using, but this works if you’ve got lookahead/lookbehind.

It works on the premise that the keys are all uppercase only, whilst the values aren’t – not sure if that’s a valid assumption, but if it’s not then as noted things will get complicated and messy.

(?<=[+-\/])[A-Z]+=(?:(?![A-Z]+=)[^=])+(?=[+-\/]|$)

And here’s my attempt to explain that (not sure how much this makes sense):

(?x)         # enable regex comment mode
(?<=[+-\/])  # start with one of the delimiters, but excluded from match
[A-Z]+       # match one or more uppercase (for the key)
=            # match the equal sign

(?:          # start non-capturing group

  (?!          # start negative lookahead, to prevent keys matching
    [A-Z]+=      # a key and equals (since in negative lookahead, this is what we exclude)
  )            # end the negative lookahead
  [^=]         # match a character that's not =

)+           # end non-capturing group, match one or more times, until...

(?=[+-\/]|$) # next char must be delimiter or end of line for match to succeed

For Java string->regex, backslashes need escaping (as would quotes, if there were any):

Pattern p = Pattern.compile("(?<=[+-\\/])[A-Z]+=(?:(?![A-Z]+=)[^=])+(?=[+-\\/]|$)");

And if capturing groups are needed, just add parens round the appropriate parts:

Pattern p = Pattern.compile("(?<=[+-\\/])([A-Z]+)=((?:(?![A-Z]+=)[^=])+(?=[+-\\/]|$))");

The matching part of this, to turn it into newline delimited text, is something like…

Matcher m = p.Matcher( InputText );
StringBuffer Result = new StringBuffer("");

while ( m.find() )
{
   Result.append( m.Group() + "\n" );
}