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
/
\[\d{1,2}:\d{2} [AP]M\] \n?([^:]*\n?):.*(\d{4}.?\d{4}.?\d{4})
/
gm
\[ matches the character [ with index 9110 (5B16 or 1338) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{1,2} matches the previous token between 1 and 2 times, as many times as possible, giving back as needed (greedy)
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
{2} matches the previous token exactly 2 times
matches the character with index 3210 (2016 or 408) literally (case sensitive)
Match a single character present in the list below
[AP]
AP
matches a single character in the list AP (case sensitive)
M matches the character M with index 7710 (4D16 or 1158) literally (case sensitive)
\] matches the character ] with index 9310 (5D16 or 1358) literally (case sensitive)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
\n
matches a line-feed (newline) character (ASCII 10)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
1st Capturing Group
([^:]*\n?)
Match a single character not present in the list below
[^:]
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
\n
matches a line-feed (newline) character (ASCII 10)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
.
matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
2nd Capturing Group
(\d{4}.?\d{4}.?\d{4})
\d
matches a digit (equivalent to [0-9])
{4} matches the previous token exactly 4 times
.
matches any character (except for line terminators)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\d
matches a digit (equivalent to [0-9])
{4} matches the previous token exactly 4 times
.
matches any character (except for line terminators)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
\d
matches a digit (equivalent to [0-9])
{4} matches the previous token exactly 4 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.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String