Regular Expressions 101

Explanation

Pro

^start of line

Non-Capturing Group(?:(\d{2}-\d{2}-\d{4}) *[-:]? *([A-Z\d].*)|([A-Z\d].*)(?<![ :-]) *[-:]? *(\d{2}-\d{2}-\d{4}))

1st Alternative(\d{2}-\d{2}-\d{4}) *[-:]? *([A-Z\d].*)

Group 1(\d{2}-\d{2}-\d{4})

\d{2}a digit, repeated exactly 2 times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d{2}a digit, repeated exactly 2 times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d{4}a digit, repeated exactly 4 times

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Character Class[-:]?

?matches at most one character from the set below:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

:the literal : (58₁₀ / 72₈ / 3A₁₆)

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Group 2([A-Z\d].*)

Character Class[A-Z\d]

A-Zone character from A (65₁₀) to Z (90₁₀) (case insensitive)

\da digit

.*any character (except for line terminators), repeated any number of times

2nd Alternative([A-Z\d].*)(?<![ :-]) *[-:]? *(\d{2}-\d{2}-\d{4})

Group 3([A-Z\d].*)

Character Class[A-Z\d]

A-Zone character from A (65₁₀) to Z (90₁₀) (case insensitive)

\da digit

.*any character (except for line terminators), repeated any number of times

Negative Lookbehind(?<![ :-])

Character Class[ :-]

the literal (32₁₀ / 40₈ / 20₁₆)

:the literal : (58₁₀ / 72₈ / 3A₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Character Class[-:]?

?matches at most one character from the set below:

-the literal - (45₁₀ / 55₈ / 2D₁₆)

:the literal : (58₁₀ / 72₈ / 3A₁₆)

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Group 4(\d{2}-\d{2}-\d{4})

\d{2}a digit, repeated exactly 2 times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d{2}a digit, repeated exactly 2 times

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d{4}a digit, repeated exactly 4 times

$end of line

the literal ↵ (10₁₀ / 12₈ / A₁₆)

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

i modifier: insensitive. Matches without distinguishing uppercase and lowercase letters

Match Information

Detailed match information will be displayed here automatically.

Quick Reference

26 tokens

Regular Expression

^(?:(\d{2}-\d{2}-\d{4}) *[-:]? *([A-Z\d].*)|([A-Z\d].*)(?<![ :-]) *[-:]? *(\d{2}-\d{2}-\d{4}))$

New

23-05-1990  Some heading
27-05-1990  Liar Liar Pants on Fire
29-05-1990  Another Heading
30-05-1990  50/50
31-05-1990  My day
Liar Liar Pants on Fire         27-05-1990
Another Heading    29-05-1990
50/50              30-05-1990
My day             31-05-1990
23-05-1990 : Some heading
27-05-1990 : Yes Man
29-05-1990: Another Heading
30-05-1990 - 50/50
31-05-1990 - My day

Substitution

$1$4 $2$3\n

23-05-1990  Some heading
27-05-1990  Liar Liar Pants on Fire
29-05-1990  Another Heading
30-05-1990  50/50
31-05-1990  My day
Liar Liar Pants on Fire         27-05-1990
Another Heading    29-05-1990
50/50              30-05-1990
My day             31-05-1990
23-05-1990 : Some heading
27-05-1990 : Yes Man
29-05-1990: Another Heading
30-05-1990 - 50/50
31-05-1990 - My day