Golang progress bar

main.go

package main

import (
	"fmt"
	"os"
	"strings"
	"time"

	"golang.org/x/term"
)

var (
	prefix         = "Progress: "
	isTerm         = term.IsTerminal(int(os.Stdout.Fd()))
	progressFormat = ternary(isTerm, "[\x1b[31m%s%s\x1b[0m]", "[%s%s]") //
)

func main() {
	if isTerm {
		_, rows, _ := term.GetSize(int(os.Stdout.Fd()))
		fmt.Printf("\x1b[%dS\x1b[r", rows) // scroll one page and reset scrolling area
	}

	for i := 0.0; i <= 100; i++ {
		fmt.Println(i)
		progress(i, 100)
		time.Sleep(25 * time.Millisecond)
	}
}

func progress(current, total float64) {
	columns, rows, err := term.GetSize(int(os.Stdout.Fd()))
	if err != nil || columns < 40 {
		columns = 80
		isTerm = false
	}

	if isTerm {
		fmt.Print("\x1b[s")              // save cursor position
		fmt.Printf("\x1b[1;%dr", rows-1) // set scrolling area
		fmt.Printf("\x1b[%d;0H", rows)   // go to last line
	}

	barSize := columns - len(prefix) - 22
	done := strings.Repeat("#", int(current)*barSize/int(total))
	rest := strings.Repeat(" ", barSize-len(done))
	percent := float64(current) / float64(total) * 100
	bar := fmt.Sprintf(progressFormat, done, rest)
	fmt.Printf("%s%s %.2f%% (%.f/%.f)\n", prefix, bar, percent, current, total)
	fmt.Printf("\x1b]2;%s%.2f%%\a", prefix, percent) // OSC escape code to set window

	if isTerm {
		if percent >= 100 {
			fmt.Print("\x1b[s")   // save cursor position
			fmt.Print("\x1b[r")   // reset scrolling area
			fmt.Println("\x1b[u") // restore cursor position and add a new line

			return
		}
		fmt.Printf("\x1b[u") // restore cursor position
	}
}

func ternary(cond bool, a, b string) string {
	if cond {
		return a
	}
	return b
}