Demonstrates the Cmd.exec command for running shell commands.

This example shows how to execute shell commands and handle both success and failure cases using pattern matching in update. The split layout shows command output in the main area with controls at the bottom.

Examples

Run the demo from the terminal:

ruby examples/widget_cmd_exec/app.rb

Source Code

# frozen_string_literal: true

#--
# SPDX-FileCopyrightText: 2026 Kerrick Long <me@kerricklong.com>
# SPDX-License-Identifier: MIT-0
#++

$LOAD_PATH.unshift File.expand_path("../../lib", __dir__)

require "ratatui_ruby"
require "ratatui_ruby/tea"

# Demonstrates the Cmd.exec command for running shell commands.
#
# This example shows how to execute shell commands and handle both success
# and failure cases using pattern matching in update. The split layout shows
# command output in the main area with controls at the bottom.
#
# === Examples
#
# Run the demo from the terminal:
#
#   ruby examples/widget_cmd_exec/app.rb
#
# rdoc-image:/doc/images/widget_cmd_exec.png
class WidgetCmdExec
  Model = Data.define(:result, :loading, :last_command)
  INITIAL = Model.new(
    result: "Press a key to run a command...",
    loading: false,
    last_command: nil
  )

  VIEW = -> (model, tui) do
    hotkey_style = tui.style(modifiers: [:bold, :underlined])
    dim_style = tui.style(fg: :dark_gray)

    # Styles
    border_color = if model.loading
      "yellow"
    elsif model.result.start_with?("Error")
      "red"
    else
      "cyan"
    end

    title = model.last_command ? "Output: #{model.last_command}" : "Cmd.exec Demo"
    content_text = model.loading ? "Running command..." : model.result

    # 1. Main Output Widget
    output_widget = tui.paragraph(
      text: content_text,
      block: tui.block(
        title:,
        borders: [:all],
        border_style: { fg: border_color },
        padding: 1
      )
    )

    # 2. Control Panel Widget
    control_widget = tui.paragraph(
      text: [
        tui.text_line(spans: [
          tui.text_span(content: "d", style: hotkey_style),
          tui.text_span(content: ": Directory listing (ls -la)  "),
          tui.text_span(content: "u", style: hotkey_style),
          tui.text_span(content: ": System info (uname -a)"),
        ]),
        tui.text_line(spans: [
          tui.text_span(content: "f", style: hotkey_style),
          tui.text_span(content: ": Force failure  "),
          tui.text_span(content: "s", style: hotkey_style),
          tui.text_span(content: ": Sleep (3s)  "),
          tui.text_span(content: "q", style: hotkey_style),
          tui.text_span(content: ": Quit"),
        ]),
      ],
      block: tui.block(
        title: "Controls",
        borders: [:all],
        border_style: dim_style
      )
    )

    # Return the Root Layout Widget (Blueprint)
    tui.layout(
      direction: :vertical,
      constraints: [
        tui.constraint_fill(1),
        tui.constraint_length(6),
      ],
      children: [
        output_widget,
        control_widget,
      ]
    )
  end

  UPDATE = -> (msg, model) do
    case msg
    # Handle command results
    in [:got_output, { stdout:, status: 0 }]
      [model.with(result: stdout.strip.freeze, loading: false), nil]
    in [:got_output, { stderr:, status: }]
      [model.with(result: "Error (exit #{status}): #{stderr.strip}".freeze, loading: false), nil]

    # Handle key presses
    in _ if msg.q? || msg.ctrl_c?
      RatatuiRuby::Tea::Cmd.quit
    in _ if msg.d?
      [model.with(loading: true, last_command: "ls -la"), RatatuiRuby::Tea::Cmd.exec("ls -la", :got_output)]
    in _ if msg.u?
      [model.with(loading: true, last_command: "uname -a"), RatatuiRuby::Tea::Cmd.exec("uname -a", :got_output)]
    in _ if msg.s?
      cmd = "sleep 3 && echo 'Slept for 3s'"
      [model.with(loading: true, last_command: cmd.freeze), RatatuiRuby::Tea::Cmd.exec(cmd, :got_output)]
    in _ if msg.f?
      # Intentional failure to demonstrate error handling
      cmd = "ls /nonexistent_path_12345"
      [model.with(loading: true, last_command: cmd.freeze), RatatuiRuby::Tea::Cmd.exec(cmd, :got_output)]
    else
      model
    end
  end

  def run
    RatatuiRuby::Tea.run(model: INITIAL, view: VIEW, update: UPDATE)
  end
end

WidgetCmdExec.new.run if __FILE__ == $PROGRAM_NAME