182 lines
4.6 KiB
Markdown
182 lines
4.6 KiB
Markdown
# env
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[](https://github.com/caarlos0/env/actions?workflow=build)
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[](https://codecov.io/gh/caarlos0/env)
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[](http://godoc.org/github.com/caarlos0/env)
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Simple lib to parse envs to structs in Go.
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## Example
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A very basic example:
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```go
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package main
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import (
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"fmt"
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"time"
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// if using go modules
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"github.com/caarlos0/env/v6"
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// if using dep/others
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"github.com/caarlos0/env"
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)
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type config struct {
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Home string `env:"HOME"`
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Port int `env:"PORT" envDefault:"3000"`
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IsProduction bool `env:"PRODUCTION"`
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Hosts []string `env:"HOSTS" envSeparator:":"`
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Duration time.Duration `env:"DURATION"`
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TempFolder string `env:"TEMP_FOLDER" envDefault:"${HOME}/tmp" envExpand:"true"`
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}
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func main() {
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cfg := config{}
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if err := env.Parse(&cfg); err != nil {
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fmt.Printf("%+v\n", err)
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}
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fmt.Printf("%+v\n", cfg)
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}
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```
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You can run it like this:
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```sh
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$ PRODUCTION=true HOSTS="host1:host2:host3" DURATION=1s go run main.go
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{Home:/your/home Port:3000 IsProduction:true Hosts:[host1 host2 host3] Duration:1s}
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```
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## Supported types and defaults
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Out of the box all built-in types are supported, plus a few others that
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are commonly used.
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Complete list:
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- `string`
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- `bool`
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- `int`
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- `int8`
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- `int16`
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- `int32`
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- `int64`
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- `uint`
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- `uint8`
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- `uint16`
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- `uint32`
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- `uint64`
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- `float32`
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- `float64`
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- `string`
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- `time.Duration`
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- `encoding.TextUnmarshaler`
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- `url.URL`
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Pointers, slices and slices of pointers of those types are also supported.
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You can also use/define a [custom parser func](#custom-parser-funcs) for any
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other type you want.
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If you set the `envDefault` tag for something, this value will be used in the
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case of absence of it in the environment.
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By default, slice types will split the environment value on `,`; you can change
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this behavior by setting the `envSeparator` tag.
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If you set the `envExpand` tag, environment variables (either in `${var}` or
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`$var` format) in the string will be replaced according with the actual value
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of the variable.
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Unexported fields are ignored.
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## Custom Parser Funcs
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If you have a type that is not supported out of the box by the lib, you are able
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to use (or define) and pass custom parsers (and their associated `reflect.Type`)
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to the `env.ParseWithFuncs()` function.
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In addition to accepting a struct pointer (same as `Parse()`), this function
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also accepts a `map[reflect.Type]env.ParserFunc`.
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`env` also ships with some pre-built custom parser funcs for common types. You
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can check them out [here](parsers/).
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If you add a custom parser for, say `Foo`, it will also be used to parse
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`*Foo` and `[]Foo` types.
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This directory contains pre-built, custom parsers that can be used with `env.ParseWithFuncs`
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to facilitate the parsing of envs that are not basic types.
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Check the example in the [go doc](http://godoc.org/github.com/caarlos0/env)
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for more info.
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## Required fields
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The `env` tag option `required` (e.g., `env:"tagKey,required"`) can be added
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to ensure that some environment variable is set. In the example above,
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an error is returned if the `config` struct is changed to:
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```go
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type config struct {
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Home string `env:"HOME"`
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Port int `env:"PORT" envDefault:"3000"`
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IsProduction bool `env:"PRODUCTION"`
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Hosts []string `env:"HOSTS" envSeparator:":"`
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SecretKey string `env:"SECRET_KEY,required"`
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}
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```
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## From file
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The `env` tag option `file` (e.g., `env:"tagKey,file"`) can be added
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to in order to indicate that the value of the variable shall be loaded from a file. The path of that file is given
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by the environment variable associated with it
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Example below
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```go
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package main
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import (
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"fmt"
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"time"
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"github.com/caarlos0/env"
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)
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type config struct {
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Secret string `env:"SECRET,file"`
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Password string `env:"PASSWORD,file" envDefault:"/tmp/password"`
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Certificate string `env:"CERTIFICATE,file" envDefault:"${CERTIFICATE_FILE}" envExpand:"true"`
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}
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func main() {
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cfg := config{}
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if err := env.Parse(&cfg); err != nil {
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fmt.Printf("%+v\n", err)
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}
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fmt.Printf("%+v\n", cfg)
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}
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```
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```sh
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$ echo qwerty > /tmp/secret
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$ echo dvorak > /tmp/password
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$ echo coleman > /tmp/certificate
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$ SECRET=/tmp/secret \
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CERTIFICATE_FILE=/tmp/certificate \
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go run main.go
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{Secret:qwerty Password:dvorak Certificate:coleman}
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```
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## Stargazers over time
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[](https://starchart.cc/caarlos0/env)
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