regex.md

regex

• reference
• negative match
• replace
• replace all characters that not match allowed
• group matches
• group matches sequence
• group replace
• optional character
• auto-escaping
• optional group

---

reference

• Character classes in regular expressions
• regex

negative match

var str = "tcpmux          1/tcp                           # TCP port service multiplexer";
var regex = new Regex(@"([^\s]*)\s*([^/]*)/([^\s]*)");
var match = regex.Match(str.Replace('\t', ' '));
var name = match.Groups[1].Value; // "tcpmux"
var port = int.Parse(match.Groups[2].Value); // "1"
var protocol = match.Groups[3].Value; // "tcp"

replace

var fullstr = "23: sample [Overtest 1]";

var rgx = new Regex(@"\d+:\s");
var str = rgx.Replace(fullstr, "");

rgx = new Regex(@"\s\[Over.*\]");
str = rgx.Replace(str, "");

• will result in "sample"

replace all characters that not match allowed

var rgx = new Regex(@"[^a-zA-Z0-9\-]");
var str = "Wrong_Host name";

• will results in "Wrong-Host-name"

group matches

var filename = "some_12.txt";

var match = new Regex(@".*_(\d+)\.txt").Match(filename);
if (match.Success) Console.WriteLine($"number is : {match.Groups[1].Value}");

group matches sequence

using System.Text.RegularExpressions;

var ODataRegexGet = new Regex(@"odata/([^/]+)$"); // note: ending $ requires no more text
var ODataRegexCount = new Regex(@"odata/([^/]+)/\$count$");

var test1 = "/odata/Some";
var test2 = "/odata/Some/$count";

Console.WriteLine($"{test1,-20} match get base  = [{ODataRegexGet.Match(test1).Success}]");
Console.WriteLine($"{test1,-20} match get count = [{ODataRegexCount.Match(test1).Success}]");

Console.WriteLine($"{test2,-20} match get base  = [{ODataRegexGet.Match(test2).Success}]");
Console.WriteLine($"{test2,-20} match get count = [{ODataRegexCount.Match(test2).Success}]");

results:

/odata/Some          match get base  = [True]
/odata/Some          match get count = [False]
/odata/Some/$count   match get base  = [False]
/odata/Some/$count   match get count = [True]

group replace

var myval = 22d;
var rgxStr = @"G1(.*)Z(.*)F(.*)";
var rgx = new Regex(rgxStr);
var line = "G1A0.000Z-4.064F300.0";
if (rgx.Match(line))
{
 var line2 = rgx.Replace(line, Invariant($"$"G1$1Z{myval}F$3"));
 // line2 = "G1A0.000Z22F300.0";
}

optional character

var regex = new Regex(@"X\s*=\s*([-]?[\d\.]*)\s*Y\s*=\s*([-]?[\d\.]*)\s*Z\s*=\s*([-]?[\d\.]*)");

var match = regex.Match("X = -187.42845697 Y = 128.44203407 Z = 25.92565607");
if (match.Success)
{
  var x = match.Groups[1].Value;
  var y = match.Groups[2].Value;
  var z = match.Groups[3].Value;
  Console.WriteLine($"coord x:{x} y:{y} z:{z}");
}

auto-escaping

var base = "(some).2";
var strangefilename = base + "_myfile.txt";

var match = new Regex(Regex.Escape(base) + @"_myfile\.txt");

optional group

var str1 = "some";
var str2 = "some_123";

var match = new Regex(@"some(?<my>(_\d*)?)");
// it will matches either str1 and str2