Some go learning notes for calling external commands

shelly.go

package main
// Always declare main for the main init part of program

import (
	"fmt"      // For printing feedback
	"os"       // For getting args
	"os/exec"  // For calling external script
	"strings"  // Std string manipulation lib
)

func numberedlines(myargs []string) {
	// The function is called with N parameters, condensed to a list
	// The following prints, for each entry, the key `k` (the int index) and the value `v` (the output line)
	for k,v := range myargs {
		// The key is a special object, whose value appears through concatenation:
		// 	fmt.Println("Got", k, v)
		//  in formatting strings, use "%v"
		//  (the odd structures \033[*m are terminal colour codes)
		fmt.Printf("\033[32;1m%v\033[0m: %s\n", k, v)
	}
}

func firstargofall(myargs...string) {
	// Unpacking
	//   we desmonstrate a function with variable number of arguments
	fmt.Println("First unpacked argument was: "+myargs[0])
}

func main() {

	// The first token is the program name itself
	//   drop it
	args := os.Args[1:]

	// Pass arguments from current program through to command to execute
	// the [ARGNAME] + '...' notation unpacks the arguments in place
	//    so that even if `args` is an array, `Command(...)` itself receives N arguments
	cmd := exec.Command("ls", args...)

	// Unpack demo
	firstargofall(args...)
	firstargofall("a", "b", "c")

	// out is stdout, err is an actual error object
	out, err := cmd.Output()

	if ( err != nil ) {
		fmt.Println("=== ERROR ===")
		fmt.Println(err)
	} else {
		// string(out) -- the output `out` is a sequence of bytes
		outlines := strings.Split(string(out), "\n")

		// Another example of unpacking
		numberedlines(outlines)
	}
}

// Try building and running this item (save as `shelly.go`)
//	go build shelly.go && ./shelly -l --color=always