initial commit

.env

@@ -0,0 +1 @@
+MY_VAR="hello world"

asd

@@ -0,0 +1 @@
+MY_VAR="bye world"

go.mod

@@ -0,0 +1,3 @@
+module git.tordarus.net/Tordarus/loadenv
+
+go 1.18

main.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"regexp"
+)
+
+var (
+	EnvFilePath = flag.String("f", ".env", "environment file")
+
+	EnvVarRegex     = regexp.MustCompile(`^(.*?)=(.*?)$`)
+	EnvCommentRegex = regexp.MustCompile(`^[ \t]*#.*?$`)
+)
+
+func main() {
+	flag.Parse()
+
+	envFile, err := os.Open(*EnvFilePath)
+	if err != nil {
+		panic(err)
+	}
+	defer envFile.Close()
+
+	envVars := parseEnvFile(envFile)
+	args := flag.Args()
+
+	newEnv := append(os.Environ(), envVars...)
+
+	if len(args) == 0 {
+		for _, envVar := range newEnv {
+			fmt.Println(envVar)
+		}
+		return
+	}
+
+	cmd := exec.Command(args[0], args[1:]...)
+	cmd.Env = newEnv
+
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+
+	if err := cmd.Run(); err != nil {
+		if exitErr, ok := err.(*exec.ExitError); ok {
+			os.Exit(exitErr.ExitCode())
+			return
+		} else {
+			panic(err)
+		}
+	}
+}
+
+func parseEnvFile(r io.Reader) []string {
+	env := make([]string, 0)
+	s := bufio.NewScanner(r)
+	l := 0
+	for s.Scan() {
+		l++
+
+		matches := EnvVarRegex.FindStringSubmatch(s.Text())
+		if len(matches) != 0 {
+			key, value := matches[1], os.ExpandEnv(matches[2])
+			env = append(env, fmt.Sprintf("%s=%s", key, value))
+		} else if !EnvCommentRegex.MatchString(s.Text()) {
+			panic(fmt.Sprintf("invalid env syntax on line %d", l))
+		}
+	}
+
+	return env
+}