Regex help with sample pattern. C#

Question

I decided to use Regex, now I have two problems :)

Given the input string "hello world [2] [200] [%8] [%1c] [%d]",

What would be an approprite pattern to match the instances of "[%8]" "[%1c]" + "[%d]" ? (So a percentage sign, followed by any length alphanumeric, all enclosed in square brackets).

for the "[2]" and [200], I already use

Regex.Matches(input, "(\\[)[0-9]*?\\]");

Which works fine.

Any help would be appreicated.

Answer 1

Try this:

Regex.Matches(input, "\\[%[0-9a-f]+\\]");

Or as a combined regular expression:

Regex.Matches(input, "\\[(\\d+|%[0-9a-f]+)\\]");

Answer 2

How about @"\[%[0-9a-f]*?\]"?

string input = "hello world [2] [200] [%8] [%1c] [%d]";
MatchCollection matches = Regex.Matches(input, @"\[%[0-9a-f]*?\]");
matches.Count // = 3

Answer 3

MatchCollection matches = null;
try {
    Regex regexObj = new Regex(@"\[[%\w]+\]");
    matches = regexObj.Matches(input);
    if (matches.Count > 0) {
     // Access individual matches using matches.Item[]
    } else {
     // Match attempt failed
    } 
} catch (ArgumentException ex) {
    // Syntax error in the regular expression
}

Answer 4

The Regex needed to match this pattern of "[%anyLengthAlphaNumeric]" in a string is this "[(%\w+)]"

The leading "[" is escaped with the "\" then you are creating a grouping of characters with the (...). This grouping is defined as %\w+. The \w is a shortcut for all word characters including letters and digits no spaces. The + matches one or more instances of the previous symbol, character or group. Then the trailing "]" is escaped with a "\" and catches the closing bracket.

Here is a basic code example:

string input = @"hello world [2] [200] [%8] [%1c] [%d]";
Regex example = new Regex(@"\[(%\w+)\]");
MatchCollection matches = example.Matches(input);