jeninh/scripting-with-go

Create executable Go scripts using a shell trick (not a true shebang). Scripts run directly like ./script.go with full argument support.

Basic pattern

First line of any Go script (choose based on your shell):

// For dash (Debian/Ubuntu default):
//usr/bin/env go run "$0" "$@"; exit

// For bash/zsh (avoids gopls formatting complaints):
/**/usr/bin/env go run "$0" "$@"; exit;

Then chmod +x script.go and run ./script.go args.

Shell compatibility:

• /**/ syntax works in bash/zsh but NOT in dash
• // syntax works in dash but gopls will complain about formatting
• Check your /bin/sh: ls -l /bin/sh
• Use //usr/bin/env go to find go in PATH
• Use //usr/local/go/bin/go for absolute path

How it works

1. OS tries to execute ./script.go as binary
2. Fails with ENOEXEC (not a binary)
3. OS falls back to /bin/sh
4. Shell runs first line: compiles and executes the script
5. $0 = script path, $@ = all arguments
6. exit (or exit;) prevents shell from interpreting remaining Go code
7. Shell normalizes //path to /path or /**/path to /path

Complete example

//usr/bin/env go run "$0" "$@"; exit
package main

import (
	"fmt"
	"os"
)

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Usage: ./script.go <name>")
		os.Exit(1)
	}
	fmt.Printf("Hello, %s!\n", os.Args[1])
}

When to use

Good for:

• Long-lived automation needing stability (Go 1.x compatibility guarantee)
• Cross-platform scripts
• Corporate environments
• Scripts that may grow into programs
• Avoiding dependency management hell

Avoid for:

• Simple one-liners
• Systems without Go
• Throwaway scripts

Common patterns

CLI flags

//usr/bin/env go run "$0" "$@"; exit
package main

import (
	"flag"
	"fmt"
)

func main() {
	verbose := flag.Bool("v", false, "verbose output")
	flag.Parse()
	fmt.Printf("Verbose: %v, Args: %v\n", *verbose, flag.Args())
}

stdin

//usr/bin/env go run "$0" "$@"; exit
package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		fmt.Println("Got:", scanner.Text())
	}
}

File operations

//usr/bin/env go run "$0" "$@"; exit
package main

import (
	"fmt"
	"os"
	"path/filepath"
)

func main() {
	filepath.Walk(".", func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if !info.IsDir() {
			fmt.Println(path)
		}
		return nil
	})
}

Notes

• Using env finds go in PATH, making scripts more portable
• Semicolon required in exit; with /**/ syntax (but not with //)
• Avoid dependencies for maximum compatibility
• Slower startup than interpreted languages (compilation time)