Regular Expression for Getting the String Values between "$$"

Question

Following is the string i get after processing the Doc File....

$$JHFIRMPHONE-91$$
$$SYSDATE-4$$
Dear  $$RCSALUTATION-5$$,
$$PAPTRANSMITTHANKS-34$$$$IPOWERPACKAGE-56$$$$CASHCARDLOADED-57$$$$CASHCARDTYPE-58$$$$ACTIVATE-59$$$$REFUNDBALANCEDUE-63$$$$FLEXPAY-68$$$$FLEXPAYCONT-67$$
$$REFBALDU$$$$EEXT-73$$
$$RALCASHCARD-64$$
$$ACRCASHCARD-65$$
$$CHECKMONEYCREDITCARD-61$$
$$NOPAYFULL-62$$
$$RAFMEMO-38$$$$RAFMEMOPT2-44$$
$$AMENDED-24$$
$$FORMSSCHEDULES-11$$
$$FORMS_LIST$$
$$FDHANDWRITTENATTACHMENTS-35$$
$$FDATTACHMENTS-26$$
$$FURNISHEDCOPIESKEEP-69$$
$$ESORDEATH-36$$
$$GOLDGUARANTEE-20$$
$$BASICGUARANTEE1-76$$$$BASICGUARANTEE2-77$$$$BASICGUARANTEE3-78$$
$$STONLYOPC-37$$
$$STATE-14$$
$$ST_DATA$$
$$STHANDWRITTENATTACHMENTS-29$$
$$STATTACHMENTS-27$$
$$TAXCOURSE-72$$
$$REWARDTYPE-82$$$$REWARDTYPE2-83$$$$REWARDTYPE3-84$$$$HEALTHBENEFITS-92$$$$HEALTHBENEFITS2-93$$$$HEALTHBENEFITS3-94$$$$HEALTHBENEFITS4-95$$$$HEALTHBENEFITS5-96$$
$$SINCERELY-40$$
$$CLOSING-16$$
$$JHTAXSERVICE-17$$
$$RAFSTARMEMO-45$$
$$RAFSTARMEMO2-97$$

What i want is,i need to get all the text values between $$ and $$.I don't know how to do this in an efficient way...i want some Regular Expression solution to solve this problem.I have very little knowledge about Regular Expression,so please guys help me in this...any efficient solution besides Regex will also do...thanks in advance...

Martin Ender · Accepted Answer · 2012-11-02 14:35:41Z

4

Here are some regex basics, worth reading up on.

As far as your specific problem is concerned:

foreach(Match match in Regex.Matches(input, @"\$\$(.*?)\$\$"))
{
    string textValue = match.Groups[1].Value;
    // process the text value
}

The regex matches, two literal $, then arbitrarily many non-linebreak characters (only as much as necessary) to get to two more $. Since matches cannot overlap, there is no danger of getting extra matches from an ending $$ to a beginning $$.

A slightly more efficient and usually recommended regex would be:

@"\$\$((?!\$\$).)*\$\$"

It basically does the same thing, just the regex internals are a bit different (have a look into "lookaheads").

In fact, if you can guarantee that the text values will always just contain letters, digits, underscores and hyphens, you can use:

@"\$\$([\w-]+)\$\$"

Not also that for all three cases, some people prefer to replace \$\$ with \${2}, but I personally find that a bit unnecessary for two repetitions.

edited Nov 2, 2012 at 14:35

answered Nov 2, 2012 at 14:28

Martin Ender

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2 Comments

Ari McBrown Over a year ago

Ah, you got me there ;)... I forgot to add lazy... Wait, it's not needed with my version.

Martin Ender Over a year ago

You don't need to add laziness, because your character classes cannot consume the $s.

L.B · Accepted Answer · 2012-11-02 14:37:26Z

1

Actually no need for regex. Your text is easy to split by String.Split.

var parts = str.Split(new string[] {"$$"}, StringSplitOptions.RemoveEmptyEntries);

answered Nov 2, 2012 at 14:37

L.B

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5 Comments

Martin Ender Over a year ago

Will catch Dear and , as well. If you want to use split, keep the empty entries and then filter out every even index.

L.B Over a year ago

@m.buettner I don't see any comment stating OP doesn't want those values.

Martin Ender Over a year ago

I assumed from the "between $$ and $$" that each text value is delimited by its own pair of $$. Well, I guess the OP would have to clarify that.

Ari McBrown Over a year ago

I think this is an rather unsafe approach, for every result you will also have an empty string result. In other words, you don't catch what you're looking for, you catch everything... needed or not

Amol Kolekar Over a year ago

thanks for help..but i was getting "Dear" also which i didn't wanted...but regex solution did its trick...:)

Ari McBrown · Accepted Answer · 2012-11-02 14:45:01Z

1

I think \$\$([A-Z0-9\_\-]+?)\$\$ should cover the load.

You might want to check extra parameters that it allows multiline parsing.

Look at this link for more detailed information about regular-expressions

edited Nov 2, 2012 at 14:45

answered Nov 2, 2012 at 14:28

Ari McBrown

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2 Comments

Martin Ender Over a year ago

This doesn't catch the line $$ST_DATA$$ (I also just discovered that one now)

Ari McBrown Over a year ago

Ah, in that case it should be a bit looser.. I'll change it immediately.

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