Regular Expressions 101

^start of line

M{0,4}the literal M (77₁₀ / 115₈ / 4D₁₆) (case sensitive), repeated between 0 and 4 times

Group 1(C[MD]|D?C{0,3})

1st AlternativeC[MD]

Cthe literal C (67₁₀ / 103₈ / 43₁₆) (case sensitive)

Character Class[MD]

Mthe literal M (77₁₀ / 115₈ / 4D₁₆) (case sensitive)

Dthe literal D (68₁₀ / 104₈ / 44₁₆) (case sensitive)

2nd AlternativeD?C{0,3}

D?optionally matches the literal D (68₁₀ / 104₈ / 44₁₆) (case sensitive)

C{0,3}the literal C (67₁₀ / 103₈ / 43₁₆) (case sensitive), repeated between 0 and 3 times

Group 2(X[CL]|L?X{0,3})

1st AlternativeX[CL]

Xthe literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive)

Character Class[CL]

Cthe literal C (67₁₀ / 103₈ / 43₁₆) (case sensitive)

Lthe literal L (76₁₀ / 114₈ / 4C₁₆) (case sensitive)

2nd AlternativeL?X{0,3}

L?optionally matches the literal L (76₁₀ / 114₈ / 4C₁₆) (case sensitive)

X{0,3}the literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive), repeated between 0 and 3 times

Group 3(I[XV]|V?I{0,3})

1st AlternativeI[XV]

Ithe literal I (73₁₀ / 111₈ / 49₁₆) (case sensitive)

Character Class[XV]

Xthe literal X (88₁₀ / 130₈ / 58₁₆) (case sensitive)

Vthe literal V (86₁₀ / 126₈ / 56₁₆) (case sensitive)

2nd AlternativeV?I{0,3}

V?optionally matches the literal V (86₁₀ / 126₈ / 56₁₆) (case sensitive)

I{0,3}the literal I (73₁₀ / 111₈ / 49₁₆) (case sensitive), repeated between 0 and 3 times

$end of line

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

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^M{0,4}(C[MD]|D?C{0,3})(X[CL]|L?X{0,3})(I[XV]|V?I{0,3})$

New

I
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
XIII
XIV
XV
XVI
XVII
XVIII
XIX
XX
XLIV
XLIX
LXXIX
XCIV
XCIX
C
CI
CII
CIII
CIV
CVI
CIX
CD
CM
CC
CCC
D
DC
DCC
DCCC
CX
CXX
CXIX
CMXCIX
MCMXLIV
MMMMCCCXII

Regular Expression

Extraction