fortio.org/progressbar

progressbar

Zero dependency cross platform (just needs basic ANSI codes and Unicode font support, and ANSI codes can be disabled too if needed) golang concurrent safe progress bar for terminal/CLIs, with 8x the resolution of others (8 steps per character).

Shows a spinner and/or a progress bar with optional prefix and extra info.

Also provides reader/writer wrappers to automatically show progress of downloads/uploads or other io operations, as well as a Writer that can be used concurrently with the progress bar to show other output on screen.

Examples

See examples/

Manually updating a progress bar and additional output

Manually handling a 2-line output update (1 misc line and the 1 line for the progress bar):

	pb := progressbar.NewBar()
	fmt.Print("Progress bar example\n\n") // 1 empty line before the progress bar, for the demo
	n := 1000
	for i := 0; i <= n; i++ {
		pb.ProgressBar(100. * float64(i) / float64(n))
		if i%63 == 0 {
			progressbar.MoveCursorUp(1)
			fmt.Printf("Just an extra demo print for %d\n", i)
		}
		time.Sleep(20 * time.Millisecond)
	}

Source: examples/simple/simple.go (-moveup mode)

Concurrent safe screen writer example

	pb := progressbar.NewBar()
	w := pb.Writer()
	fmt.Fprintln(w, "Progress bar example")
	// demonstrate concurrency safety:
	go PrintStuff(w, *everyFlag)
	// exact number of 'pixels', just to demo every smooth step:
	n := pb.Width * 8
	for i := 0; i <= n; i++ {
		pb.ProgressBar(100. * float64(i) / float64(n))
		time.Sleep(*delayFlag)
	}

go run fortio.org/progressbar/examples/simple@latest -color

Produces

Or without color:

◅███████████████████████████▊            ▻ 69.4%

Source: examples/simple/example.go (default mode)

Automatic Reader or Writer progress bar

	reader := progressbar.NewAutoReader(progressbar.NewBar(), resp.Body, resp.ContentLength)
	_, err = io.Copy(os.Stdout, reader)
	reader.Close()

See it in action with a progress bar while downloading a URL:

go run fortio.org/progressbar/examples/auto@latest https://go.dev/ > go_dev.html

Will show a progress bar for instance

$  go run ./examples/auto https://go.dev/dl/go1.24.1.src.tar.gz > /dev/null
Fetching https://go.dev/dl/go1.24.1.src.tar.gz
⣾ █████████████████████▌                   53.7% 15.766 Mb out of 29.352 Mb, 293ms elapsed, 53.790 Mb/s, 253ms remaining

Source (now includes a multi bar separating R/W): auto_examples/auto/auto_example.go

Multiple Bars updating concurrently

	cfg := progressbar.DefaultConfig()
	cfg.ExtraLines = 1
	cfg.ScreenWriter = os.Stdout
	mbar := cfg.NewMultiBarPrefixes(
		"b1",
		"longest prefix",
		"short",
		"b4",
	)
	wg := sync.WaitGroup{}
	for i, bar := range mbar {
		wg.Add(1)
		// Update at random speed so bars move differently for a demo:
		delay := time.Duration(5+rand.IntN(40)) * time.Millisecond
		bar.WriteAbove(fmt.Sprintf("\t\t\tBar %d delay is %v", i+1, delay))
		go func(b *progressbar.State) {
			UpdateBar(b, delay)
			wg.Done()
		}(bar)
	}
	wg.Wait()
	progressbar.MultiBarEnd(mbar)

Complete source: multi_example/multi_example.go

Which includes adding extra bars dynamically.

Multicurl

You can see it in use in fortio/multicurl cli too.

See also

If you have more advanced needs for TUI including raw mode input or readline, you can also see/use/have a look at

github.com/fortio/terminal

And still use this for a progress bar part.

It is used for instance in github.com/fortio/fps's web mode progress update

And grol's multi file processing progress info (make grol-tests)