[lxc-devel] [lxd/master] lxc/progress: Add terminal detection

[stgraber on Github]

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From 35366b7413d37a6118a0fc3d23f90ed94866db78 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber at ubuntu.com>
Date: Tue, 9 Oct 2018 13:21:24 -0400
Subject: [PATCH] lxc/progress: Add terminal detection
MIME-Version: 1.0
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Closes: https://github.com/lxc/lxc/issues/2683

Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
---
 lxc/utils/progress.go | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/lxc/utils/progress.go b/lxc/utils/progress.go
index 3b5ebcf48d..13f1eef689 100644
--- a/lxc/utils/progress.go
+++ b/lxc/utils/progress.go
@@ -2,12 +2,14 @@ package utils
 
 import (
 	"fmt"
+	"os"
 	"strings"
 	"sync"
 	"time"
 
 	"github.com/lxc/lxd/shared/api"
 	"github.com/lxc/lxd/shared/ioprogress"
+	"github.com/lxc/lxd/shared/termios"
 )
 
 // ProgressRenderer tracks the progress information
@@ -19,6 +21,22 @@ type ProgressRenderer struct {
 	wait      time.Time
 	done      bool
 	lock      sync.Mutex
+	terminal  int
+}
+
+func (p *ProgressRenderer) truncate(msg string) string {
+	width, _, err := termios.GetSize(int(os.Stdout.Fd()))
+	if err != nil {
+		return msg
+	}
+
+	newSize := len(msg)
+	if width < newSize {
+		newSize = width
+	}
+
+	msg = msg[0:newSize]
+	return msg
 }
 
 // Done prints the final status and prevents any update
@@ -45,6 +63,9 @@ func (p *ProgressRenderer) Done(msg string) {
 		return
 	}
 
+	// Truncate msg to terminal length
+	msg = p.truncate(msg)
+
 	// Print the new message
 	if msg != "" {
 		msg += "\n"
@@ -82,6 +103,19 @@ func (p *ProgressRenderer) Update(status string) {
 		return
 	}
 
+	// Skip status updates when not dealing with a terminal
+	if p.terminal == 0 {
+		if !termios.IsTerminal(int(os.Stdout.Fd())) {
+			p.terminal = -1
+		}
+
+		p.terminal = 1
+	}
+
+	if p.terminal != 1 {
+		return
+	}
+
 	// Print the new message
 	msg := "%s"
 	if p.Format != "" {
@@ -90,6 +124,9 @@ func (p *ProgressRenderer) Update(status string) {
 
 	msg = fmt.Sprintf("\r"+msg, status)
 
+	// Truncate msg to terminal length
+	msg = p.truncate(msg)
+
 	if len(msg) > p.maxLength {
 		p.maxLength = len(msg)
 	} else {
@@ -114,6 +151,9 @@ func (p *ProgressRenderer) Warn(status string, timeout time.Duration) {
 	p.wait = time.Now().Add(timeout)
 	msg := fmt.Sprintf("\r%s", status)
 
+	// Truncate msg to terminal length
+	msg = p.truncate(msg)
+
 	if len(msg) > p.maxLength {
 		p.maxLength = len(msg)
 	} else {