regex101: Parse Docker image reference components (URI / tag / name / registry / host)

^start of line

Group Name(?<Name>(?<=^)(?:(?<Domain>(?:(?:localhost|[\w-]+(?:\.[\w-]+)+)(?::\d+)?)|[\w]+:\d+)\/)?\/?(?<Namespace>(?:(?:[a-z0-9]+(?:(?:[._]|__|[-]*)[a-z0-9]+)*)\/)*)(?<Repo>[a-z0-9-]+))

Positive Lookbehind(?<=^)

^start of line

Non-Capturing Group(?:(?<Domain>(?:(?:localhost|[\w-]+(?:\.[\w-]+)+)(?::\d+)?)|[\w]+:\d+)\/)?

?repeats the group contents below at most once:

Group Domain(?<Domain>(?:(?:localhost|[\w-]+(?:\.[\w-]+)+)(?::\d+)?)|[\w]+:\d+)

1st Alternative(?:(?:localhost|[\w-]+(?:\.[\w-]+)+)(?::\d+)?)

Non-Capturing Group(?:(?:localhost|[\w-]+(?:\.[\w-]+)+)(?::\d+)?)

Non-Capturing Group(?:localhost|[\w-]+(?:\.[\w-]+)+)

1st Alternativelocalhost

localhostthe literal text localhost (case sensitive)

2nd Alternative[\w-]+(?:\.[\w-]+)+

Character Class[\w-]+

+matches at least one character from the set below:

\wany word character

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Non-Capturing Group(?:\.[\w-]+)+

+repeats the group contents below at least once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

Character Class[\w-]+

+matches at least one character from the set below:

\wany word character

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Non-Capturing Group(?::\d+)?

?repeats the group contents below at most once:

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\d+a digit, repeated at least once

2nd Alternative[\w]+:\d+

Character Class[\w]+

+matches at least one character from the set below:

\wany word character

:the literal : (58₁₀ / 72₈ / 3A₁₆)

\d+a digit, repeated at least once

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

\/?optionally matches the literal / (47₁₀ / 57₈ / 2F₁₆)

Group Namespace(?<Namespace>(?:(?:[a-z0-9]+(?:(?:[._]|__|[-]*)[a-z0-9]+)*)\/)*)

Non-Capturing Group(?:(?:[a-z0-9]+(?:(?:[._]|__|[-]*)[a-z0-9]+)*)\/)*

*repeats the group contents below any number of times:

Non-Capturing Group(?:[a-z0-9]+(?:(?:[._]|__|[-]*)[a-z0-9]+)*)

Character Class[a-z0-9]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Non-Capturing Group(?:(?:[._]|__|[-]*)[a-z0-9]+)*

*repeats the group contents below any number of times:

Non-Capturing Group(?:[._]|__|[-]*)

1st Alternative[._]

Character Class[._]

.the literal . (46₁₀ / 56₈ / 2E₁₆)

_the literal _ (95₁₀ / 137₈ / 5F₁₆)

2nd Alternative__

__the literal text __

3rd Alternative[-]*

Character Class[-]*

Character Class[a-z0-9]+

\/the literal / (47₁₀ / 57₈ / 2F₁₆)

Group Repo(?<Repo>[a-z0-9-]+)

Character Class[:@]?

Group Reference(?<Reference>(?<=:)(?<Tag>[\w][\w.-]{0,127})|(?<=@)(?<Digest>[A-Za-z][A-Za-z0-9]*(?:[-_+.][A-Za-z][A-Za-z0-9]*)*[:][0-9A-Fa-f]{32,}))?

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

Search reference

Regular Expression

^(?<Name>(?<=^)(?:(?<Domain>(?:(?:localhost|[\w-]+(?:\.[\w-]+)+)(?::\d+)?)|[\w]+:\d+)\/)?\/?(?<Namespace>(?:(?:[a-z0-9]+(?:(?:[._]|__|[-]*)[a-z0-9]+)*)\/)*)(?<Repo>[a-z0-9-]+))[:@]?(?<Reference>(?<=:)(?<Tag>[\w][\w.-]{0,127})|(?<=@)(?<Digest>[A-Za-z][A-Za-z0-9]*(?:[-_+.][A-Za-z][A-Za-z0-9]*)*[:][0-9A-Fa-f]{32,}))?

Unit Tests

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