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
/
^[A-Za-z\d@!?\-_.]{5,}$
/
gm
^ asserts position at start of a line
Match a single character present in the list below
[A-Za-z\d@!?\-_.]
{5,} matches the previous token between 5 and unlimited times, as many times as possible, giving back as needed (greedy)
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
a-z matches a single character in the range between a (index 97) and z (index 122) (case sensitive)
\d matches a digit (equivalent to [0-9])
@!?
matches a single character in the list @!? (case sensitive)
\- matches the character - with index 4510 (2D16 or 558) literally (case sensitive)
_.
matches a single character in the list _. (case sensitive)
$ asserts position at the end of a line
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

/
/
gm

Test String