Regular Expressions 101

Save & Share

Flavor

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

Function

  • Match
  • Substitution
  • List
  • Unit Tests
"
(?!CT)\d{2}
"
gm
Negative Lookahead
(?!CT)
Assert that the Regex below does not match
CT
matches the characters CT literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{2} matches the previous token exactly 2 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)
Your regular expression does not match the subject string.

Regular Expression
No Match

r"
"
gm

Test String