opcilloscope

A lightweight, cross-platform OPC UA client for the terminal.

Browse, monitor, and subscribe to industrial automation data right from your terminal. Keyboard-driven with mouse support. No bloated GUI, no complex setup, no license fees.

Why opcilloscope?

Use cases: commissioning (verify PLC tags), troubleshooting (live values during fault diagnosis), integration testing (validate OPC UA server configs), recording (export to CSV for reports).

Features

• Browse — Lazily explore the OPC UA address space. Expand only what you need.
• Monitor — Subscribe to variables with Enter. Receive OPC UA monitored-item notifications instead of polling values.
• Inspect — Full node attributes: Description, DataType, AccessLevel, ValueRank.
• Scope — Real-time multi-signal oscilloscope (up to 5 signals, 30 s sliding window).
• Record — Export selected monitored variables to CSV. Notifications are queued with full-precision, locale-independent values (ISO 8601 UTC timestamps, . decimal separator, arrays as semicolon-joined elements). A bounded queue protects the UI if storage falls behind, and any dropped records are reported when recording stops.
• Configure — Save/load connection and subscription configs (.cfg JSON files).
• Themes — Dark (default), light, and terminal (inherits your terminal's ANSI colour scheme).

Scope view — a soothing sine wave

OPC UA Server
  │  samples monitored items (250 ms requested by default)
  │  delivers subscription notifications (250 ms publishing interval by default)
  ▼
opcilloscope receives data-change notifications
  ├─→ Scope View     — retains up to 2,000 numeric samples per signal while open
  └─→ CSV Recording  — queues selected-variable notifications for background writes

Keyboard Shortcuts

Install

Linux / macOS:

curl -fsSL https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/install.sh | bash

Windows (PowerShell):

irm https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/install.ps1 | iex

Or grab a binary from GitHub Releases.

Release archives include the self-contained executable, the project license, and notices for bundled third-party components. The installers preserve those notices in an app-owned license directory.

The installers require the matching release checksum and refuse an unverified download. On Windows, the default install directory is added to your user PATH; a custom OPCILLOSCOPE_INSTALL_DIR is treated as shared and leaves PATH unchanged.

macOS note: the binaries are unsigned, so archives downloaded with a browser are quarantined by Gatekeeper. Either use the curl installer above, or clear the quarantine attribute after extracting: xattr -d com.apple.quarantine <binary>.

Then run:

opcilloscope

An automatic/omitted or partial security profile requires a SignAndEncrypt endpoint and selects the strongest matching candidate offered by the server. Explicit securityMode: "Sign" opts into signed-but-unencrypted traffic. Explicit anonymous securityMode: "None" opts into unsecured plaintext; username authentication never permits None.

Server certificates that fail validation are rejected by default. For a development server, opcilloscope --insecure disables server certificate validation for that run; it does not enable plaintext transport. Do not use this option in production. The connection log reports the trusted-certificate store path when validation fails.

curl -fsSL https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/uninstall.sh | bash

rm ~/.local/bin/opcilloscope
rm -rf "${XDG_DATA_HOME:-$HOME/.local/share}/opcilloscope/licenses"
rm -rf "${XDG_CONFIG_HOME:-$HOME/.config}/opcilloscope"  # optional: configs and recent files
rm -rf "${XDG_DATA_HOME:-$HOME/.local/share}/opcilloscope/pki"  # optional: certificates

rm ~/.local/bin/opcilloscope
rm -rf "$HOME/Library/Application Support/opcilloscope/licenses"
rm -rf "$HOME/Library/Application Support/opcilloscope/configs"  # optional
rm -f "$HOME/Library/Application Support/opcilloscope/recent-files.json"  # optional
rm -rf "$HOME/Library/Application Support/opcilloscope/pki"  # optional: certificates

irm https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/uninstall.ps1 | iex

$installDir = "$env:LOCALAPPDATA\Programs\opcilloscope"
Remove-Item "$installDir\opcilloscope.exe" -Force
Remove-Item "$installDir\opcilloscope-licenses" -Recurse -Force
$userPath = [Environment]::GetEnvironmentVariable("Path", "User")
$pathEntries = @($userPath -split ";" | Where-Object { $_.Trim().TrimEnd('\') -ine $installDir.TrimEnd('\') })
[Environment]::SetEnvironmentVariable("Path", ($pathEntries -join ";"), "User")
Remove-Item "$env:APPDATA\opcilloscope" -Recurse -Force             # optional: configs and recent files
Remove-Item "$env:LOCALAPPDATA\opcilloscope\pki" -Recurse -Force    # optional: certificates

Quickstart (Developer)

Requires .NET 10 SDK.

git clone https://github.com/SquareWaveSystems/opcilloscope.git
cd opcilloscope
dotnet build Opcilloscope.sln
dotnet run --project Opcilloscope.csproj

Run the cross-platform unit, integration, and component suite:

dotnet test Opcilloscope.sln

On Linux, also exercise a freshly published binary through the real PTY E2E harness:

dotnet test Tests/Opcilloscope.E2ETests/Opcilloscope.E2ETests.csproj

See docs/TESTING.md for test layers and exact-artifact usage.

OPC UA Test Servers

Built-in test server (Counter, SineWave, RandomValue, writable nodes):

dotnet run --project Tests/Opcilloscope.TestServer
# Starts at opc.tcp://localhost:4840/UA/OpcilloscopeTest

Public servers (no setup required):

Docker (Microsoft OPC PLC):

docker run -p 50000:50000 mcr.microsoft.com/iotedge/opc-plc:latest \
  --autoaccept --unsecuretransport
# Connect to opc.tcp://localhost:50000

Contributing

Contributions welcome! Please submit an issue or a pull request, and see CONTRIBUTING.md for development and review guidance.

License

The opcilloscope source code is MIT-licensed — see LICENSE.

Official binary releases are self-contained builds that bundle the OPC Foundation UA .NET Standard stack and other third-party components. The bundled stack version (1.5.378.156) is distributed by the OPC Foundation under its MIT license; earlier versions of that stack were dual-licensed GPL-2.0/RCL. See THIRD-PARTY-NOTICES.md for the full list of bundled components and their licenses.

Built by Square Wave Systems
Inspired by lazygit