Environment Variables {.en}

环境变量 {.zh}

::: {.en} Environment variables are a universal mechanism for conveying configuration information to Unix programs. Let’s look at how to set, get, and list environment variables. :::

::: {.zh}

[环境变量]（http://en.wikipedia.org/wiki/Environment_variable）是[将配置信息传递给Unix程序]的通用机制（http://www.12factor.net/config）。让我们来看看如何设置，获取和列出环境变量。

:::

package main
import "os"
import "strings"
import "fmt"
func main() {

::: {.en} To set a key/value pair, use os.Setenv. To get a value for a key, use os.Getenv. This will return an empty string if the key isn’t present in the environment. :::

::: {.zh}

要设置键/值对，请使用os.Setenv。要获得密钥的价值，请使用os.Getenv。如果该环境中不存在该键，则将返回空字符串。

:::

    os.Setenv("FOO", "1")
    fmt.Println("FOO:", os.Getenv("FOO"))
    fmt.Println("BAR:", os.Getenv("BAR"))

::: {.en} Use os.Environ to list all key/value pairs in the environment. This returns a slice of strings in the form KEY=value. You can strings.Split them to get the key and value. Here we print all the keys. :::

::: {.zh}

使用os.Environ列出环境中的所有键/值对。这将返回形式为“KEY = value”的字符串片段。你可以strings.Split他们忘记关键和价值。在这里，我们打印所有的键。

:::

    fmt.Println()
    for _, e := range os.Environ() {
        pair := strings.Split(e, "=")
        fmt.Println(pair[0])
    }
}

::: {.en} Running the program shows that we pick up the value for FOO that we set in the program, but that BAR is empty. :::

::: {.zh}

运行该程序表明我们获取了我们在程序中设置的“FOO”的值，但是'#BAR为空。

:::

$ go run environment-variables.go
FOO: 1
BAR:

::: {.en} The list of keys in the environment will depend on your particular machine. :::

::: {.zh}

环境中的键列表将取决于您的特定机器。

:::

TERM_PROGRAM
PATH
SHELL
...

::: {.en} If we set BAR in the environment first, the running program picks that value up. :::

::: {.zh}

如果我们首先在环境中设置“BAR”，则运行程序会选择该值。

:::

$ BAR=2 go run environment-variables.go
FOO: 1
BAR: 2
...