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

/
/
g

Test String

Code Generator

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"(\/)(\*)(.|\n)*?\2\1|(\/\/.*)"; string input = @"#include<stdio.h> #include<stdlib.h> typedef struct Node { int data; struct Node *next; struct Node *prev; }node; void insert(node *pointer, int data) { /* Iterate through the list till we encounter the last node.*/ while(pointer->next!=NULL) { pointer = pointer -> next; } /* Allocate memory for the new node and put data in it.*/ pointer->next = (node *)malloc(sizeof(node)); (pointer->next)->prev = pointer; pointer = pointer->next; pointer->data = data; pointer->next = NULL; } int find(node *pointer, int key) { pointer = pointer -> next; //First node is dummy node. /* Iterate through the entire linked list and search for the key. */ while(pointer!=NULL) { if(pointer->data == key) //key is found. { return 1; } pointer = pointer -> next;//Search in the next node. } /*Key is not found */ return 0; } void delete(node *pointer, int data) { /* Go to the node for which the node next to it has to be deleted */ while(pointer->next!=NULL && (pointer->next)->data != data) { pointer = pointer -> next; } if(pointer->next==NULL) { printf(""Element %d is not present in the list\n"",data); return; } /* Now pointer points to a node and the node next to it has to be removed */ node *temp; temp = pointer -> next; /*temp points to the node which has to be removed*/ pointer->next = temp->next; temp->prev = pointer; /*We removed the node which is next to the pointer (which is also temp) */ free(temp); /* Beacuse we deleted the node, we no longer require the memory used for it . free() will deallocate the memory. */ return; } void print(node *pointer) { if(pointer==NULL) { return; } printf(""%d "",pointer->data); print(pointer->next); } int main() { /* start always points to the first node of the linked list. temp is used to point to the last node of the linked list.*/ node *start,*temp; start = (node *)malloc(sizeof(node)); temp = start; temp -> next = NULL; temp -> prev = NULL; /* Here in this code, we take the first node as a dummy node. The first node does not contain data, but it used because to avoid handling special cases in insert and delete functions. */ printf(""1. Insert\n""); printf(""2. Delete\n""); printf(""3. Print\n""); printf(""4. Find\n""); while(1) { int query; scanf(""%d"",&query); if(query==1) { int data; scanf(""%d"",&data); insert(start,data); } else if(query==2) { int data; scanf(""%d"",&data); delete(start,data); } else if(query==3) { printf(""The list is ""); print(start->next); printf(""\n""); } else if(query==4) { int data; scanf(""%d"",&data); int status = find(start,data); if(status) { printf(""Element Found\n""); } else { printf(""Element Not Found\n""); } } } }"; foreach (Match m in Regex.Matches(input, pattern)) { 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