Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression

/
/
gm

Test String

Code Generator

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"l4.1"; string input = @"// Lab 4.1 #include <iostream> #include <stdlib.h> using namespace std; int n, m; int a[21], b[21], c[42]; // Cau 1 void createArray() { int i; do { cout << "" - Nhap gia tri cua n: ""; cin >> n; } while (10 > n || n > 20); // Khoi tao 2 mang A & B co n phan tu for (i = 0; i < n; i++) { a[i] = rand() % 490 + 10; b[i] = rand() % 490 + 10; } } void printArray(int *array, int len) { int i; for (i = 0; i < len; i++) { cout << ""\t"" << array[i]; } cout << endl; } void chanA_LeB() { int i, j; j = 0; for (i = 0; i < n; i++) { if (a[i] % 2 == 0) { c[j] = a[i]; j++; } if (b[i] % 2 != 0) { c[j] = b[i]; j++; } } m = j; } int mul_is_safe(int a, int b) { if (b > INT_MAX / a) return 0; return 1; } void mulArray() { int i, j; long long KQ; KQ = 1; for (i = 0; i < m; i++) { if (mul_is_safe(c[i], KQ)) { cout << c[i]; KQ *= c[i]; for (j = i-1; j >= 0; j--) { if (i != 0) cout << "" * "" << c[j]; } cout << "" = "" << KQ << endl; } else { cout << ""Integer Overflow"" << endl << endl; return; } } } int main() { // Cau 1 cout << ""Cau 1: "" << endl; createArray(); // Cau 2 cout << endl << ""Cau 2: "" << endl; cout << "" - Mang A: "" << endl; printArray(a, n); cout << "" - Mang B: "" << endl; printArray(b, n); // Cau 3 cout << endl << ""Cau 3: "" << endl; chanA_LeB(); cout << "" - Mang C: "" << endl; printArray(c, m); // Cau 4 cout << endl << ""Cau 4: "" << endl; mulArray(); //system(""pause""); return 0; } "; RegexOptions options = RegexOptions.Multiline; foreach (Match m in Regex.Matches(input, pattern, options)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx