Multibar

Note: This entire codebase was vibe-coded.

Lightweight terminal progress bars with multi-bar support and thread-safe updates.

Features

• Multiple progress bars rendered together (multi-bar)
• Smooth partial block characters (▏▎▍▌▋▊▉█)
• Spinner while bars are running
• Percentage, elapsed time, and ETA
• ETA is hidden when a bar is finished
• Safe to update bars from multiple goroutines

Install

go get github.com/metalim/multibar

Quick start

mb := multibar.New()
bar := mb.NewBar(100, "Downloading")
mb.Start()
for i := 0; i < 100; i++ {
    bar.Add(1)
    time.Sleep(10 * time.Millisecond)
}
// If max is undefined (multibar.Undefined), finish explicitly:
// bar.Finish()

Multi-bar example

See examples/multibar/main.go.

mb := multibar.New()
workBar := mb.NewBar(multibar.Undefined, "Working")
workersBar := mb.NewBar(len(files), fmt.Sprintf("Workers (0/%d)", len(files)))
bytesBar := mb.NewBar64(totalSize, "Total bytes")
mb.Start()
var wg sync.WaitGroup
for _, f := range files {
    fileBar := mb.NewBar64(f.Size, f.Name)
    wg.Add(1)
    go func(b *multibar.Bar, f File) {
        for j := int64(0); j < f.Size; j++ {
            workBar.Add(1)
            bytesBar.Add(1)
            b.Add(1)
            time.Sleep(10 * time.Millisecond)
        }
        workersBar.Add(1)
        workersBar.SetDescription(fmt.Sprintf("Workers (%d/%d)", workersBar.Value(), workersBar.Max()))
        wg.Done()
    }(fileBar, f)
}
wg.Wait()
workBar.Finish() // for the undefined bar

API (essentials)

• multibar.New(opts ...Option) *MultiBar
  • WithWriter(w io.Writer) — redirect output (default os.Stdout)
• (*MultiBar).NewBar(max int, desc string) *Bar
• (*MultiBar).NewBar64(max int64, desc string) *Bar
• (*MultiBar).Start() — start rendering
• (*Bar).Add(n int64) — add progress
• (*Bar).SetValue(v int64) — set current value
• (*Bar).SetMax(max int64) — set max
• (*Bar).SetDescription(desc string) — change description
• (*Bar).Finish() — finish the bar (required for Undefined)
• (*Bar).Value(), (*Bar).Max() — getters
• Constant: multibar.Undefined — bar with unknown max

Time behavior

• Elapsed freezes when the bar is finished
• ETA is hidden for finished bars
• Layout: percentage, elapsed (yellow), ETA (cyan)

Thread-safety

• Bar mutations guarded by an internal sync.Mutex
• MultiBar.render() is serialized by a dedicated renderMu to avoid interleaved lines
• Access to MultiBar internals guarded by mu; render snapshots state under lock and prints without it

Output format

⠴ Downloading █████████████▉        69% 0:01:09 0:01:40

• For finished bars the spinner becomes a space, the bar turns green, and ETA is hidden

License

MIT