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
No Match

/
/
gmxXi

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 = "# ./configure parser\n\n" + "^(?:\n" + " (?:configuring[[:space:]]for[[:space:]](.+))\n" + " |\n" + " (?:\n" + " checking[[:space:]]\n" + " (?:\n" + " (?:build|host)\n" + " [[:space:]]system[[:space:]]type\n" + " |\n" + " how[[:space:]]to[[:space:]](.+?)\n" + " |\n" + " for[[:space:]](.+?)\n" + " |\n" + " whether[[:space:]](?:to[[:space:]])?(.+?)\n" + " )[\\.]{3}\n" + " )\n" + " (?:\n" + " [[:space:]]+\n" + " (?:\n" + " $\n" + " |\n" + " (?:\n" + " (yes)\n" + " |\n" + " (no)\n" + " |\n" + " (?<!^)(.*)(?=$|\\n)\n" + " )\n" + " )\n" + " )?.*\n" + ")$\n\n" + "# ^(?:(?:configuring[[:space:]]for[[:space:]](.+))|(?:checking[[:space:]](?:(?:build|host)[[:space:]]system[[:space:]]type|how[[:space:]]to[[:space:]](.+?)|for[[:space:]](.+?)|whether[[:space:]](?:to[[:space:]])?(.+?))[\\.]{3})(?:[[:space:]]+(?:$|(?:(yes)|(no)|(?<!^)(.*)(?=$|\\n))))?.*)$"; final String string = "configuring for zsh 5.7.1-test-2\n" + "checking build system type... x86_64-apple-darwin17.7.0\n" + "checking host system type... x86_64-apple-darwin17.7.0\n" + "checking for gcc... gcc\n" + "checking whether the C compiler works... yes\n" + "checking for C compiler default output file name... a.out\n" + "checking for suffix of executables... \n" + "checking whether we are cross compiling... no\n" + "checking for suffix of object files... o\n" + "checking whether we are using the GNU C compiler... yes\n" + "checking whether gcc accepts -g... yes\n" + "checking for gcc option to accept ISO C89... none needed\n" + "checking for special C compiler options needed for large files... no\n" + "checking for _FILE_OFFSET_BITS value needed for large files... no\n" + "checking how to run the C preprocessor... gcc -E\n" + "checking for an ANSI C-conforming const... yes\n" + "checking for gcc option to accept ANSI C... \n" + "checking whether to use prototypes... yes\n" + "checking for grep that handles long lines and -e... /usr/local/bin/ggrep\n" + "checking for egrep... /usr/local/bin/ggrep -E\n" + "checking for ANSI C header files... yes\n" + "checking for sys/types.h... yes\n" + "checking for sys/stat.h... yes\n" + "checking for stdlib.h... yes\n" + "checking for string.h... yes\n" + "checking for memory.h... yes\n" + "checking for strings.h... yes\n" + "checking for inttypes.h... yes\n" + "checking for stdint.h... yes\n" + "checking for unistd.h... yes\n" + "checking for size_t... yes\n" + "checking for working alloca.h... yes"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.COMMENTS | Pattern.CASE_INSENSITIVE); 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