How to show stdout of a command into a viewport

[nihal-innsof]

I need to automate some task using go and bubbletea. And i need to print the output of the executed command in realtime into a viewport. How can this be achieved. Thanks in advance

[meowgorithm]

Hi! Here’s a simple program to get you started:

package main

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"os/exec"

	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
)

const viewportHeight = 8

type pingMsg string

type pingErrMsg struct{ err error }

type pingDoneMsg struct{}

func ping(domain string, sub chan string) tea.Cmd {
	return func() tea.Msg {
		// Setup the command
		cmd := exec.Command("ping", "-c", "10", domain)
		out, err := cmd.StdoutPipe()
		if err != nil {
			return pingErrMsg{err}
		}

		// Run the command.
		if err := cmd.Start(); err != nil {
			return pingErrMsg{err}
		}

		// Read command output as it arrives.
		buf := bufio.NewReader(out)
		for {
			line, _, err := buf.ReadLine()
			if err == io.EOF {
				return pingDoneMsg{}
			}
			if err != nil {
				return pingErrMsg{err}
			}
			// Send output to our program.
			sub <- string(line)
		}
	}
}

func waitForPingResponses(sub chan string) tea.Cmd {
	return func() tea.Msg {
		// Send the ping to Update.
		return pingMsg(<-sub)
	}
}

type model struct {
	sub      chan string
	result   *string
	viewport viewport.Model
}

func newModel() model {
	m := model{
		result:   new(string),
		sub:      make(chan string),
		viewport: viewport.New(0, viewportHeight),
	}
	m.appendOutput("Pinging...")
	return m
}

func (m model) Init() tea.Cmd {
	return tea.Batch(ping("charm.sh", m.sub), waitForPingResponses(m.sub))
}

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	var cmds []tea.Cmd

	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		m.viewport.Width = msg.Width
		return m, nil
	case tea.KeyMsg:
		switch msg.String() {
		case "q", "ctrl+c", "esc":
			return m, tea.Quit
		}
	case pingMsg:
		m.appendOutput(string(msg))
		cmds = append(cmds, waitForPingResponses(m.sub))
	case pingErrMsg:
		m.appendOutput("Error: " + msg.err.Error())
	case pingDoneMsg:
		m.appendOutput("Done. Press ^C to exit.")
	}

	var cmd tea.Cmd
	m.viewport, cmd = m.viewport.Update(msg)

	cmds = append(cmds, cmd)
	return m, tea.Batch(cmds...)
}

func (m *model) appendOutput(s string) {
	*m.result += "\n" + s
	m.viewport.SetContent(*m.result)
	m.viewport.GotoBottom()
}

func (m model) View() string {
	return m.viewport.View()
}

func main() {
	p := tea.NewProgram(newModel())
	if _, err := p.Run(); err != nil {
		fmt.Println("Oh no", err)
		os.Exit(1)
	}
}

[nihal-innsof]

Thanks, this helped me figure it out.