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,}))?

Test String
New

alpine
alpine:latest
localhost/latest
library/alpine
localhost:1234/test
test:1234/blaboon
alpine:3.7
docker.example.edu/gmr/alpine:3.7
docker.example.com:5000/gmr/alpine@sha256:5a156ff125e5a12ac7ff43ee5120fa249cf62248337b6d04abc574c8
docker.example.co.uk/gmr/alpine/test2:latest
registry.dobby.org/dobby/dobby-servers/arthound:2019-08-08
owasp/zap:3.8.0
registry.dobby.co/dobby/dobby-servers/github-run:2021-10-04
docker.elastic.co/kibana/kibana:7.6.2
registry.dobby.org/dobby/dobby-servers/lerphound:latest
registry.dobby.org/dobby/dobby-servers/marbletown-poc:2021-03-29
marbles/marbles:v0.38.1
registry.dobby.org/dobby/dobby-servers/loophole@sha256:5a156ff125e5a12ac7ff43ee5120fa249cf62248337b6d04abc574c8
sonatype/nexon:3.30.0
prom/node-exporter:v1.1.1
sosedoff/pgweb@sha256:5a156ff125e5a12ac7ff43ee5120fa249cf62248337b6d04abc574c8
sosedoff/pgweb:latest
registry.dobby.org/dobby/dobby-servers/arpeggio:2021-06-01
registry.dobby.org/dobby/antique-penguin:release-production
dalprodictus/halcon:6.7.5
antigua/antigua:v31
weblate/weblate:4.7.2-1
redis:4.0.01-alpine
registry.dobby.com/dobby/dobby-servers/github-run:latest

Regular Expression

Test StringNew

Test String
New