Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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
No Match

@"
"
gm

Test String

Substitution

Processing...

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)modelBuilder\.Entity<(?'type'\w+)>\(builder =>\n\s*\{(?'builder'[\w\W]+?)\}\);`) var str = `modelBuilder.Entity<Foobar>(builder => { builder.HasKey(e => e.Id).HasName("PRIMARY"); builder .ToTable("foobar") .UseCollation("utf8mb4_0900_ai_ci"); builder.HasIndex(e => e.A, "A").IsUnique(); builder.Property(e => e.D).HasColumnType("datetime"); builder.Property(e => e.E) .HasMaxLength(255) .UseCollation("utf8mb4_unicode_ci"); builder.Property(e => e.N) .HasMaxLength(255) .UseCollation("utf8mb4_unicode_ci"); builder.HasOne(d => d.ANav).WithOne(p => p.BNav) .HasForeignKey<Foobar>(d => d.Leerling) .HasConstraintName("Foobar_fk"); });` var substitution = "public class $1Mapping : IEntityTypeConfiguration<$1>\n{\n public void Configure(EntityTypeBuilder<$1> builder)\n {\n$2\n}}" fmt.Println(re.ReplaceAllString(str, substitution)) }

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 Golang, please visit: https://golang.org/pkg/regexp/