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

/
/
g

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`\/\\*[^*]*\\*+(?:[^\/*][^*]*\\*+)*\/|\/\/.*`) var str = `import android.content.res.Resources; import android.os.Handler; import android.preference.PreferenceFragment; import android.view.ViewGroup; * Provides the regex to identify domain HTTP(S) protocol and/or 'www' sub-domain. * * Used to format user-facing {@link String}'s in certain preferences. */ public static final String ADDRESS_FORMAT_REGEX = "^(https?://(w{3})?|www\\.)"; /** // Used to ensure that settings are only fetched once throughout the lifecycle of the fragment private boolean mShouldFetch; public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // use a wrapper to apply the Calypso theme Context themer = new ContextThemeWrapper(getActivity(), R.style.Calypso_SiteSettingsTheme); LayoutInflater localInflater = inflater.cloneInContext(themer); View view = super.onCreateView(localInflater, container, savedInstanceState); if (view != null) { setupPreferenceList((ListView) view.findViewById(android.R.id.list), getResources()); } return view; } @Override public void onChildViewAdded(View parent, View child) { if (child.getId() == android.R.id.title && child instanceof TextView) { // style preference category title views TextView title = (TextView) child; WPPrefUtils.layoutAsBody2(title); } else { // style preference title views TextView title = (TextView) child.findViewById(android.R.id.title); if (title != null) WPPrefUtils.layoutAsSubhead(title); } } @Override public void onChildViewRemoved(View parent, View child) { // NOP } @Override` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", 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 Golang, please visit: https://golang.org/pkg/regexp/