# Regular Expressions 101

## Flavor

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

• Match
• Substitution
• List
• Unit Tests

## Tools

"
(^[A-Z]{2}[:] ?)?\d+\|(([A-Z]{2}, ?)*)[A-Z]{2} \"\w+\"?
"
gm
1st Capturing Group
(^[A-Z]{2}[:] ?)?
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
^ asserts position at start of a line
Match a single character present in the list below
[A-Z]
{2} matches the previous token exactly 2 times
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
Match a single character present in the list below
[:]
: matches the character : with index 5810 (3A16 or 728) literally (case sensitive)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
\d
matches a digit (equivalent to [0-9])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\| matches the character | with index 12410 (7C16 or 1748) literally (case sensitive)
2nd Capturing Group
(([A-Z]{2}, ?)*)
3rd Capturing Group
([A-Z]{2}, ?)*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
A repeated capturing group will only capture the last iteration. Put a capturing group around the repeated group to capture all iterations or use a non-capturing group instead if you're not interested in the data
Match a single character present in the list below
[A-Z]
{2} matches the previous token exactly 2 times
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
, matches the character , with index 4410 (2C16 or 548) literally (case sensitive)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
Match a single character present in the list below
[A-Z]
{2} matches the previous token exactly 2 times
A-Z matches a single character in the range between A (index 65) and Z (index 90) (case sensitive)
matches the character with index 3210 (2016 or 408) literally (case sensitive)
\" matches the character " with index 3410 (2216 or 428) literally (case sensitive)
\w
matches any word character (equivalent to [a-zA-Z0-9_])
+ matches the previous token between one and unlimited times, as many times as possible, giving back as needed (greedy)
\"
matches the character " with index 3410 (2216 or 428) literally (case sensitive)
? matches the previous token between zero and one times, as many times as possible, giving back as needed (greedy)
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.

r"
"
gm