在Windows中使用.env文件设置环境变量

Question

I am working on a set of projects that use .env files for configuration, where each .env file exports a number of environment variables. The files are setup like;

export VARIABLE1=foo

I use the Windows Linux subsystem a lot for this, but would like to also be able to run these projects on my windows machine. The projects in question are Golang.

IS there any easy way to programatically set Windows environment variables (preferably termporarily) from these .env files? These is mostly so I can debug within VSCode.

Answer 1

Package os

import "os"

func Clearenv()
func Environ() []string
func Expand(s string, mapping func(string) string) string
func ExpandEnv(s string) string
func Getenv(key string) string
func Setenv(key, value string) error
func Unsetenv(key string) error

Read the env file lines using bufio.Scanner. Parse the lines using the strings package. Use the os package environment variable functions.

For example,

package main

import (
    "bufio"
    "bytes"
    "fmt"
    "io"
    "os"
    "strings"
)

func parseLine(line string) (key, value string) {
    line = strings.TrimSpace(line)
    const export = `export `
    if !strings.HasPrefix(line, export) {
        return "", ""
    }
    line = strings.TrimPrefix(line, export)
    fields := strings.SplitN(line, "=", 2)
    if len(fields) > 0 {
        key = strings.TrimSpace(fields[0])
        if len(fields) > 1 {
            value = strings.TrimSpace(fields[1])
        }
    }
    return key, value
}

func setenv(r io.Reader) error {
    s := bufio.NewScanner(r)
    for s.Scan() {
        line := s.Text()
        key, value := parseLine(line)
        if len(key) < 1 {
            continue
        }
        err := os.Setenv(key, value)
        if err != nil {
            return err
        }
    }
    if err := s.Err(); err != nil {
        return err
    }
    return nil
}

func main() {
    envFile := bytes.NewBufferString(
        "export VARIABLE1=foo
export VARIABLE2=bar
",
    )
    err := setenv(envFile)
    if err != nil {
        fmt.Fprintln(os.Stderr, err)
        return
    }
    for _, key := range []string{`VARIABLE1`, `VARIABLE2`} {
        env, found := os.LookupEnv(key)
        fmt.Println(key, found, env)
    }
}

Playground: https://play.golang.org/p/pZKQ0GW5eCu

Output:

VARIABLE1 true foo
VARIABLE2 true bar