Regular Expressions 101

Save & Share

  • Save Regex
    ctrl+s
  • Update Regex
    ctrl+⇧+s

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8

Function

  • Match
  • Substitution
  • List
  • Unit Tests
/
(?=\b(?:Что|в)\b)(.{5})
/
gmui
Positive Lookahead
(?=\b(?:Что|в)\b)
Assert that the Regex below matches
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
Non-capturing group
(?:Что|в)
1st Alternative
Что
Что
matches the characters Что literally (case insensitive)
2nd Alternative
в
в matches the character в with index 107410 (43216 or 20628) literally (case insensitive)
\b assert position at a word boundary: (^\w|\w$|\W\w|\w\W)
1st Capturing Group
(.{5})
.
matches any character, including unicode (except for line terminators)
{5} matches the previous token exactly 5 times
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
u modifier: unicode. Pattern strings are treated as UTF-16. Also causes escape sequences to match unicode characters
i modifier: insensitive. Case insensitive match (ignores case of [a-zA-Z])
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gmui

Test String

Code Generator

Generated Code

Loading code sample...
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/