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src/docs/markdown/extending-caddy/placeholders.md
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@ -4,9 +4,9 @@ title: "Placeholder Support"
# Placeholders
In Caddy, placeholders are a feature of the individual plugins. They are not parsed at config time, but instead preserved, and replaced at runtime.
In Caddy, placeholders are processed by each individual plugin themselves. They are not parsed at config time, but instead preserved and processed at runtime.
This means that if you wish for your plugin to support placeholders, you must explicitly add support for it.
This means that if you wish for your plugin to support placeholders, you must explicitly add support for them.
If you are not yet familiar with placeholders, start by reading [here](/docs/conventions#placeholders)!
@ -75,18 +75,18 @@ When you adapt this Caddyfile with `HOST=example caddy adapt` you will get
Importantly, look at the `"body"` field in both `srv0` and `srv1`.
Since `srv0` used `{$ENV}`, the special environmental variable replacement with `$` became `example`, as it is parsed during Caddyfile parse time.
Since `srv0` used `{$HOST}`, the special environmental variable replacement with `$`, the value became `example`, as it was processed during Caddyfile parse time.
Since `srv1` used `{env.HOST}`, a normal placeholder, it was parsed as its own raw string value, `{env.HOST}`
This means that down the line, the handler the plugins within `srv0` and `srv1` will receive the raw values `example` and `{env.Host}` respectively in their configurations.
Some users may immediately notice that this means it is impossible to use the `{$ENV}` syntax in a JSON config. The solution to this is to process such placeholders at Provision time, which is covered below.
## How to Placeholders in your Plugin
## How to use Placeholders in your Plugin
#### Parse the raw Placeholder in your unmarshaler
#### Parse the raw Placeholder value in your unmarshaler
Placeholders should be parsed as their raw values when parsing the Cazddyfile, just like any other string value
Placeholders should be parsed as their raw values when parsing the Cazddyfile, just like any other string value.
```go
func (g *Gizmo) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
@ -115,7 +115,7 @@ func (g *Gizmo) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp
#### Alternatively, resolve the Placeholder during Provision
If you only use global placeholders, like `env`, then you may initialize a global replacer at provision time, and use it to replace such values.
If you only use global placeholders, like `env`, then you may initialize a global replacer at provision time, and use it to replace such values. This also allows users of config file formats other than Caddyfile to use environmental variables.
```go
func (g *Gizmo) Provision(ctx caddy.Context) error {