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

r"
"
gm

Test String

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(extralibs_)(|avutil|avcodec|avformat|avdevice|avfilter|avresample|postproc|swscale|swresample)(?==)"; final String string = "extralibs_avutil=\"-pthread -lva-drm -lva -lvdpau -lX11 -lm -L/usr/lib64/valgrind -ldrm -lm -lcoregrind-amd64-linux -lvex-amd64-linux -lgcc -lmfx -lstdc++ -ldl -lOpenCL -lva -ldl\"\n" + "extralibs_avcodec=\"-lvpx -lm -lpthread -lvpx -lm -lpthread -lvpx -lm -lpthread -lvpx -lm -lpthread -lwebpmux -lm -lwebp -lm -pthread -pthread -lm -llzma -ldav1d -pthread -ldl -lsnappy -lstdc++ -lz -laom -lm -lpthread -lfdk-aac -lm -lgsm -lmp3lame -lm -lopenjp2 -lm -lopus -lm -lspeex -lm -ltheoraenc -ltheoradec -logg -lvorbis -lm -logg -lvorbisenc -lvorbis -lm -logg -lwebp -lm -pthread -lx264 -lpthread -lm -ldl -L/usr//usr/lib64 -lx265 -lstdc++ -lm -lgcc_s -lgcc -lgcc_s -lgcc -lrt -ldl -lnuma -lxvidcore -lva -ldl -lmfx -lstdc++ -ldl\"\n" + "extralibs_avformat=\"-lm -lxml2 -lz -llzma -lm -lbz2 -lvapoursynth-script -lpython3.8 -lcrypt -lpthread -ldl -lutil -lm -lvapoursynth -lzimg -ldl -lzimg -lstdc++ -lbluray -ldl -lpthread -lxml2 -lz -llzma -lm -lfontconfig -luuid -lexpat -lfreetype -lbz2 -lpng16 -lm -lz -lm -lz -lharfbuzz -lm -lglib-2.0 -pthread -lpcre -pthread -lgraphite2 -lbrotlidec -lbrotlicommon -lz -lssl -lcrypto -lz -ldl -pthread -lrtmp -lz -lgmp -lgnutls -pthread -lgmp -lunistring -latomic -ltasn1 -lidn2 -lp11-kit -lhogweed -lgmp -lnettle -lsrt -lstdc++ -lm -lgcov -lgcc_s -lgcc -lpthread -lc -lgcc_s -lgcc -lssl -lcrypto -lz -ldl -pthread\"\n" + "extralibs_avdevice=\"-lm -L/usr/lib64/valgrind -ldrm -lm -lcoregrind-amd64-linux -lvex-amd64-linux -lgcc -lxcb -lXau -lXdmcp -lxcb-shm -lxcb -lXau -lXdmcp -lxcb-shape -lxcb -lXau -lXdmcp -lxcb-xfixes -lxcb-render -lxcb-shape -lxcb -lXau -lXdmcp -lGL\"\n" + "extralibs_avfilter=\"-pthread -lm -lfribidi -lass -lm -lfontconfig -luuid -lexpat -lfribidi -lfreetype -lbz2 -lpng16 -lm -lz -lm -lz -lharfbuzz -lm -lglib-2.0 -pthread -lpcre -pthread -lgraphite2 -lbrotlidec -lbrotlicommon -lnppig -lnppicc -lnppc -lnppidei -lva -lvidstab -lm -lgomp -lpthread -lzimg -lstdc++ -lOpenCL -lfontconfig -luuid -lexpat -lfreetype -lbz2 -lpng16 -lm -lz -lm -lz -lharfbuzz -lm -lglib-2.0 -pthread -lpcre -pthread -lgraphite2 -lbrotlidec -lbrotlicommon -lfreetype -lbz2 -lpng16 -lm -lz -lm -lz -lharfbuzz -lm -lglib-2.0 -pthread -lpcre -pthread -lgraphite2 -lbrotlidec -lbrotlicommon -ldl -lmfx -lstdc++ -ldl\"\n" + "extralibs_avresample=\"-lm\"\n" + "extralibs_postproc=\"-lm\"\n" + "extralibs_swscale=\"-lm\"\n" + "extralibs_swresample=\"-lm\"\n"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

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 Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html