Mega Code Archive
0652 Word Boundaries
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The word boundary assertion \b matches where word characters (\w) adjoin either:
Nonword characters (\W)
The beginning/end of the string (^ and $)
\b is often used to match whole words.
For example:
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main(string[] args)
{
foreach (Match m in Regex.Matches ("This is a test", @"\b\w+\b")) {
Console.WriteLine (m);
}
}
}
The output:
This
is
a
test
The following statements highlight the effect of a word boundary:
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main(string[] args)
{
int one = Regex.Matches ("This is a test", @"\bis\b").Count;
Console.WriteLine(one);
int two = Regex.Matches ("This isn't a test", @"is").Count;
Console.WriteLine(two);
}
}
The output:
1
2
The next query uses positive lookahead to return words followed by "(is)":
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main(string[] args)
{
string text = "This (is) a test";
Console.Write (Regex.Match (text, @"\b\w+\b\s(?=\(is\))"));
}
}
The output:
This
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