---
description: components and formatting examples used in Docker's docs
title: Code blocks
toc_max: 3
---

Rouge provides lots of different code block "hints". If you leave off the hint,
it tries to guess and sometimes gets it wrong. These are just a few hints that
we use often.

## Variables

If your example contains a placeholder value that's subject to change,
use the format `<[A-Z_]+>` for the placeholder value: `<MY_VARIABLE>`

```none
export name=<MY_NAME>
```

This syntax is reserved for variable names, and will cause the variable to
be rendered in a special color and font style.

## Highlight lines

```text {hl_lines=[7,8]}
incoming := map[string]interface{}{
    "asdf": 1,
    "qwer": []interface{}{},
    "zxcv": []interface{}{
        map[string]interface{}{},
        true,
        int(1e9),
        "tyui",
    },
}    
```

````markdown
```go {hl_lines=[7,8]}
incoming := map[string]interface{}{
    "asdf": 1,
    "qwer": []interface{}{},
    "zxcv": []interface{}{
        map[string]interface{}{},
        true,
        int(1e9),
        "tyui",
    },
}   
```
````

## Collapsible code blocks

```dockerfile {collapse=true}
# syntax=docker/dockerfile:1

ARG GO_VERSION="1.21"

FROM golang:${GO_VERSION}-alpine AS base
ENV CGO_ENABLED=0
ENV GOPRIVATE="github.com/foo/*"
RUN apk add --no-cache file git rsync openssh-client
RUN mkdir -p -m 0700 ~/.ssh && ssh-keyscan github.com >> ~/.ssh/known_hosts
WORKDIR /src

FROM base AS vendor
# this step configure git and checks the ssh key is loaded
RUN --mount=type=ssh <<EOT
  set -e
  echo "Setting Git SSH protocol"
  git config --global url."git@github.com:".insteadOf "https://github.com/"
  (
    set +e
    ssh -T git@github.com
    if [ ! "$?" = "1" ]; then
      echo "No GitHub SSH key loaded exiting..."
      exit 1
    fi
  )
EOT
# this one download go modules
RUN --mount=type=bind,target=. \
    --mount=type=cache,target=/go/pkg/mod \
    --mount=type=ssh \
    go mod download -x

FROM vendor AS build
RUN --mount=type=bind,target=. \
    --mount=type=cache,target=/go/pkg/mod \
    --mount=type=cache,target=/root/.cache \
    go build ...
```

## Bash

Use the `bash` language code block when you want to show a Bash script:

```bash
#!/usr/bin/bash
echo "deb https://download.docker.com/linux/ubuntu noble stable" | sudo tee /etc/apt/sources.list.d/docker.list
```

If you want to show an interactive shell, use `console` instead.
In cases where you use `console`, make sure to add a dollar character
for the user sign:

```console
$ echo "deb https://download.docker.com/linux/ubuntu noble stable" | sudo tee /etc/apt/sources.list.d/docker.list
```

## Go

```go
incoming := map[string]interface{}{