[ALL] Regular Expressions: Parsing Strings of Text

Regular Expressions Parsing Strings of Text
For all supported programming languages.

Note that all C# examples requires that you place "using System.Text.RegularExpressions;" on top of your code file.

Not much going on here yet, so I give to you: Regular Expressions!

There are times when you may need to process a long or short text string. This string may contain only a single piece of information that you need in order to get your application up running. You could of course use the classic approach, trim the string from left and right until you get what you want. This is however not a very clean solution to the problem.

Regular Expressions might seem overly complex and difficult for beginners, and yes, it may take some time to learn. The usefulness however, makes it all worth it.

Example Take the following text string as an example:

As you can see, there's a whole lot of info we do not need. For the Windows 7 OEM SLP Key Collection we would probably want to get the manufacturer, the PID and the key itself - but for now, lets get only the key to keep it simple.

Consider the following regex:

Code:

(?i)(?<ProductKey>\w{5}-\w{5}-\w{5}-\w{5}-\w{5})

• (?i) means that the text will be matches case insensitive, as opposed to case sensitive.
• (?<ProductKey>[...]) disregard the [...]. This is the capturing group, or more precisely, the named capturing group. This is where our product key will be stored after it has been matched.
• \w{5} means that a word character (letter or number) will be matched 5 times exactly.

So how would we go about getting the result of the regex into a separate string?

[C#]:

Code:

string productKey = Regex.Match(theExampleStringHere, @"(?i)(?<ProductKey>\w{5}-\w{5}-\w{5}-\w{5}-\w{5})").Groups["ProductKey"].Value;

[AutoIt v3]:

Code:

$productKey = StringRegExp($theExampleStringHere, "(?i)(?<ProductKey>\w{5}-\w{5}-\w{5}-\w{5}-\w{5})", 3, 1)
$productKey = $productKey[0] ; This is an array where 0 represents the first element, which is out match.

Note: If you need a regex to validate Microsoft product keys, I suggest you use the one posted by MasterDisaster as his version also takes illegal product key characters into account.

All right, let's get the Windows edition as well:

Code:

(?i)(?<Edition>Starter|Home\s?(Basic|Premium)|Professional|Ultimate)

\s? means that there might be a space here, so both HomeBasic and Home Basic will be matched.

The result?

[C#]:

Code:

string edition = Regex.Match(theExampleStringHere, @"(?i)(?<Edition>Starter|Home\s?(Basic|Premium)|Professional|Ultimate)").Groups["Edition"].Value;

[AutoIt v3]:

Code:

$edition = StringRegExp($theExampleStringHere, "(?i)(?<Edition>Starter|Home\s?(Basic|Premium)|Professional|Ultimate)", 3, 1)
$edition = $edition[0] ; This is an array where 0 represents the first element, which is out match.

You can probably figure out how to obtain the manufacturer as well, even though that's a little harder since the list of manufacturers is so long.

Questions about regular expressions or maybe contributions of examples are most welcome here. Note that I am not a regex ninja, so I might not always be able to answer.

 

You could write it this way:

Code:

(?i)(?:[BCDFGHJKMPQRTV-Y2-9]{5}-){4}[BCDFGHJKMPQRTV-Y2-9]{5}

You can remove that (?i) if you want it to only match upper case characters.

 

Yep that's correct.

Btw, that ?: in the beginning tells the regex engine that the contents inside the parenthesis should not be treated as a capturing group.

 

Unbelievable, a regular expressions validator that doesn't support case insensitive matching

Does it work if you set EnableClientScript=false like this guy?

Eventually, it's dirty, but it should do the job:

Code:

ValidationExpression="^(?:[bcdfghjkmpqrtvBCDFGHJKMPQRTV-Y2346-9]{5}-){4}[bcdfghjkmpqrtvBCDFGHJKMPQRTV-Y2346-9]{5}$"

 

Ops yeah I forgot those, whether you write v-y or vwxy doesn't matter - I would choose the first one since it is four characters shorter

But if someone with a cleaner solution to the RegularExpressionValidator problem happens to walk by, please stop here and explain.

 

I think Mastering Regular Expressions (MRE) (the unofficial regex bible ) is probably one of the best books on the subject. As a quick reference book, I use Regular Expression: Pocked Reference (heavily based on MRE) a lot myself.

This article is pretty good, but it targets .NET developers. What programming/scripting language will you be using?

 

I think the easiest way to get a good feeling with regex is to have a problem then apply a regex-based solution to that problem. I'll try to show some of the logic behind regex matching:

Code:

\d{5}

\d = digit; alone this will match a number (0-9)
{5} = match the previous expression exactly 5 times, in other words: 5 numbers, will be matched.

\d is the same as \d{1}

Apply this to a string:

Code:

01546531658454

Our expression will return the first 5 digits; 01546

The following string is slightly modified:

Code:

01A546531658454

Notice that 'A'. Our expression will not return anything because A is not a digit. To match the first five characters (digits and letters) we modify our expression:

Code:

(\w\d){5}

\w = normal characters

Now everything inside the parenthesis will be matched exactly 5 times. This expression will return 01A54.


Note that I'm more a Windows applications type of developer, but you might be able to find some useful resources here. To help visualize how regular expressions matches, you might find this application interesting. It's well worth the money.

Please ask if you want to know how to match something, and I will try to explain