CODEWITHSUNDEEP
c#regexsplit
shadonar
shadonar

Reputation: 1194

regex use with newlines and spaces

I have a text file I'm reading with a C# program and am needing to split it's contents. I decided to use Regex.Split().

The pattern I am trying to look for is \n( )+Copyright

here's an example of the text:

\r\n\r\nLANGUAGE: ENGLISH\r\n\r\nDISTRIBUTION: Every Zone\r\n\r\nPUBLICATION-TYPE: Newspaper\r\n\r\n\r\n Copyright 2014 Washingtonpost.Newsweek Interactive Company, LLC d/b/a\r\n Washington Post Digital\r\n All Rights Reserved\r\n"

the reason for the newline being included is because I also have instances where the word copyright shows up in a paragraph:

\r\n\r\nFrom Blood Aces by Doug Swanson, to be published by Viking, a member of Penguin\r\nGroup (USA) LLC on Aug. 14, 2014. Copyright © 2014 by Doug J. Swanson.\r\n

however the problem i have is when I perform this call:

var splitContent= Regex.Split(filecontent, @"\n( )+Copyright");

i get over 2x as many items in splitContent as there should be. I've tried modifying the regex pattern to @"(\n){1}?( )+Copyright" and a few other similar type patterns I get 4-5x the number of items in splitContent I should be getting.

Is this the correct way to be performing this kind of regex?

Any help would be greatly appreciated.

Upvotes: 0

Views: 152

Answers (2)

Nicholas Carey
Nicholas Carey

Reputation: 74197

Why try to reinvent the wheel? Just change your regular expression to use the correct options:

RegexOptions options     = RegexOptions.Multiline
                         | RegexOptions.Ignorecase
                         ;
Regex        rxCopyright = new Regex( "^\s*Copyright", options );

string[]     lines       = rxCopyright.Split( yourStringHere ) ;

RegexOptions.Multiline tells the regular expression engine to

Use multiline mode, where ^ and $ match the beginning and end of each line (instead of the beginning and end of the input string). For more information, see Multiline Mode.

So your corpus of text will be split into blocks using the word copyright if at the beginning of any line (with or without leading whitespace).

And if you want to use parentheses for clarity, add RegexOptions.ExplicitCapture to the mix. It

Specifies that the only valid captures are explicitly named or numbered groups of the form (?<name>…). This allows unnamed parentheses to act as noncapturing groups without the syntactic clumsiness of the expression (?:…).

Upvotes: 0

user4003407
user4003407

Reputation: 22102

If capturing parentheses are used in a Regex.Split expression, any captured text is included in the resulting string array. For example, if you split the string "plum-pear" on a hyphen placed within capturing parentheses, the returned array includes a string element that contains the hyphen.

using System;
using System.Text.RegularExpressions;

public class Example
{
   public static void Main()
   {
      string input = "plum-pear";
      string pattern = "(-)";

      string[] substrings = Regex.Split(input, pattern);    // Split on hyphens 
      foreach (string match in substrings)
      {
         Console.WriteLine("'{0}'", match);
      }
   }
}
// The example displays the following output:
//    'plum'
//    '-'
//    'pear'

Regex.Split

Upvotes: 1

Related Questions