initial commit

.gitignore

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+loadenv
+*.env

LICENSE.md

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+Copyright (c) 2022 Mila Ringwald
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# loadenv
+
+Loads environment files before running a command without polluting your environment
+
+## Source code
+
+You can find the source code here: [git.milar.in](https://git.milar.in/milarin/loadenv)
+
+## Installation
+
+If you have Go installed, you can simply go install the program: `go install git.milar.in/milarin/loadenv@latest`
+
+There are pre-compiled executables for various platforms on the [repository](https://git.milar.in/milarin/loadenv/releases).
+
+## License
+
+Distributed under the MIT License. See [LICENSE.md](https://git.milar.in/milarin/loadenv/src/branch/main/LICENSE.md)
+
+## Usage
+
+`loadenv` loads the environment file provided via `-f` into the environment and runs the command provided after the arguments.
+If no file is provided, `.env` is used by default.
+If no command is provided, `loadenv` prints all environment variables to stdout.
+
+---
+
+The variables will only be available to the given command. They will be deleted after the command exits.
+`loadenv` can be useful when working with programs which heavily use environment variables.
+
+```sh
+$ cat .env
+# production server configuration
+DATABASE_HOST=prod-server.com
+DATABASE_USER=milarin
+DATABASE_PASS=my-super-secure-password
+
+$ # show the 3 last added env variables
+$ loadenv | tail -n 3
+DATABASE_HOST=prod-server.com
+DATABASE_USER=milarin
+DATABASE_PASS=my-super-secure-password
+
+$ cat dev.env
+# development server configuration
+DATABASE_HOST=dev-server.com
+DATABASE_USER=milarin
+DATABASE_PASS=my-super-secure-password
+
+$ # load dev.env into environment and run the command env. show last 3 lines
+$ loadenv -f dev.env env | tail -n 3
+DATABASE_HOST=dev-server.com
+DATABASE_USER=milarin
+DATABASE_PASS=my-super-secure-password
+```
+
+environment variables in that file will be expanded:
+
+```sh
+$ env | grep USER # current value of $USER
+USER=milarin
+
+$ cat .env
+# expand $USER reference
+USERNAME=$USER
+
+$ loadenv | tail -n 1
+USERNAME=milarin
+```
+

expand_files.go

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+package main
+
+import (
+	"bytes"
+	"io"
+	"os"
+)
+
+func expandEnvFiles() error {
+	for _, path := range FlagExpandEnvFiles {
+		tmpFile, err := os.CreateTemp("", "*")
+		if err != nil {
+			return err
+		}
+		defer tmpFile.Close()
+
+		ExpandEnvFiles[path] = tmpFile.Name()
+
+		file, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		defer file.Close()
+
+		data, err := io.ReadAll(file)
+		if err != nil {
+			return err
+		}
+		file.Close()
+
+		if _, err := io.Copy(tmpFile, bytes.NewReader(data)); err != nil {
+			return err
+		}
+
+		newFile, err := os.Create(path)
+		if err != nil {
+			return err
+		}
+		defer newFile.Close()
+
+		if _, err := newFile.WriteString(os.ExpandEnv(string(data))); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func restoreEnvFiles() error {
+	for originalFilePath, tmpFilePath := range ExpandEnvFiles {
+		originalFile, err := os.Create(originalFilePath)
+		if err != nil {
+			return err
+		}
+		defer originalFile.Close()
+
+		tmpFile, err := os.Open(tmpFilePath)
+		if err != nil {
+			return err
+		}
+		defer tmpFile.Close()
+
+		if _, err := io.Copy(originalFile, tmpFile); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

go.mod

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+module git.tordarus.net/tordarus/loadenv
+
+go 1.18

go.sum

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+git.milar.in/milarin/buildinfo v1.0.0 h1:tw98GupUYl/0a/3aPGuezhE4wseycOSsbcLp70hy60U=
+git.milar.in/milarin/buildinfo v1.0.0/go.mod h1:arI9ZoENOgcZcanv25k9y4dKDUhPp0buJrlVerGruas=

main.go

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+package main
+
+import (
+	"bufio"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"os/signal"
+	"regexp"
+	"syscall"
+)
+
+var (
+	EnvVarRegex     = regexp.MustCompile(`^(.*?)=(.*?)$`)
+	EnvCommentRegex = regexp.MustCompile(`^[ \t]*#.*?$`)
+	ExpandEnvFiles  = map[string]string{}
+)
+
+var ( // flags
+	FlagEnvFilePath = flag.String("f", ".env", "environment file")
+
+	FlagExpandEnvFiles = SliceFlag{}
+)
+
+func main() {
+	flag.Var(&FlagExpandEnvFiles, "e", "files in which to expand environment variables")
+	flag.Parse()
+
+	envFile, err := os.Open(*FlagEnvFilePath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "could not open file '%s': %s\n", *FlagEnvFilePath, err.(*os.PathError).Err)
+		return
+	}
+	defer envFile.Close()
+
+	parseEnvFile(envFile)
+	args := flag.Args()
+
+	if len(args) == 0 {
+		for _, envVar := range os.Environ() {
+			fmt.Println(envVar)
+		}
+		return
+	}
+
+	if err := expandEnvFiles(); err != nil {
+		fmt.Fprintf(os.Stderr, "could not expand files: %s\n", err.Error())
+		return
+	}
+	defer restoreFiles()
+
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
+	go func() { <-sigs; exit(1) }()
+
+	cmd := exec.Command(args[0], args[1:]...)
+	cmd.Env = os.Environ()
+
+	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 {
+			exit(exitErr.ExitCode())
+			return
+		} else {
+			panic(err)
+		}
+	}
+}
+
+func parseEnvFile(r io.Reader) {
+	s := bufio.NewScanner(r)
+	l := 0
+
+	for s.Scan() {
+		l++
+
+		matches := EnvVarRegex.FindStringSubmatch(s.Text())
+		if len(matches) != 0 {
+			os.Setenv(matches[1], matches[2])
+		} else if s.Text() != "" && !EnvCommentRegex.MatchString(s.Text()) {
+			panic(fmt.Sprintf("invalid env syntax on line %d", l))
+		}
+	}
+}
+
+func exit(errorCode int) {
+	restoreFiles()
+	os.Exit(errorCode)
+}
+
+func restoreFiles() {
+	if err := restoreEnvFiles(); err != nil {
+		fmt.Fprintf(os.Stderr, "could not restore expanded files: %s\n", err.Error())
+	}
+}

sliceflag.go

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+package main
+
+import "strings"
+
+type SliceFlag []string
+
+func (f *SliceFlag) String() string {
+	return strings.Join(*f, ",")
+}
+
+func (f *SliceFlag) Set(value string) error {
+	*f = append(*f, value)
+	return nil
+}