hwatch
hwatch is a modern replacement for the Unix watch command, written in Rust, that records command output history and enables side-by-side diff viewing, JSON logging, and trigger-based actions on change. It provides a terminal UI with customizable keymaps and supports ANSI colors, dynamic diff plugins, and cross-platform installation.
Key facts
Objective fields from the source. Values we can't verify are shown as “Unknown” rather than guessed.
| Field | Value |
|---|---|
| Repository | blacknon/hwatch |
| Owner | blacknon |
| Primary language | Rust |
| License | MIT — OSI-approved |
| Stars | 1k |
| Forks | 29 |
| Open issues | 10 |
| Latest release | 0.4.2 (2026-04-29) |
| Last updated | 2026-06-24 |
| Source | https://github.com/blacknon/hwatch |
What hwatch is
A Rust-based CLI tool that monitors command output at regular intervals, maintaining an in-memory history (configurable up to 5000 records), rendering diffs via pluggable dynamic libraries, and supporting PTY execution for color preservation. Logs output as JSONL, executes hook commands on detected changes via environment-passed JSON metadata, and offers batch and interactive TUI modes.
Get the hwatch source
Clone the repository and explore it locally.
git clone https://github.com/blacknon/hwatch.gitcd hwatch# follow the project's README for install & configurationNeed it deployed, integrated, or customized instead? DEV.co ships production installs.
Best use cases
Implementation considerations
- Dynamic diff plugins load native libraries; only load from trusted sources. Validate plugin provenance in automated deployments.
- PTY mode (`--use-pty`) required for colored output; trade-off between fidelity and capture. Test with target applications before production rollout.
- History limit (default 5000 records) must be tuned for memory constraints; unbounded recording (limit 0) risks OOM on long-running monitors.
- Aftercommand execution receives change metadata via `${HWATCH_DATA}` JSON env var or temp file; ensure robust parsing and error handling in hooks.
- Interval precision depends on command execution time; use `--precise` to enforce timing constraints, but account for system load variability.
When to avoid it — and what to weigh
- Real-time high-frequency monitoring (sub-second intervals) — Minimum interval is 2 seconds by default; designed for moderate polling cadences, not sub-second reactive systems.
- Untrusted or dynamic command input in production — The tool executes commands directly via shell or PTY. If input is user-supplied or remote, injection risks require strict input validation outside hwatch.
- Large-scale distributed logging without aggregation layer — JSONL logging is local-only and suitable for single-node use. Production infrastructure should pipe logs to centralized systems (ELK, Splunk, etc.).
- Windows-primary or heterogeneous OS environments without testing — While Windows binaries are published, primary development is Linux-focused. Compatibility in heterogeneous environments requires validation.
License & commercial use
MIT License: permissive, allows commercial use, modification, and distribution with no warranty. Requires attribution and license copy in derivative works.
MIT is a permissive OSI license. Commercial use is explicitly permitted provided the license and copyright notice are retained. No royalties, restrictions on proprietary derivatives, or commercial restrictions apply. Verify compliance with internal policies if embedding or repackaging.
DEV.co evaluation signals
Editorial assessment — not user reviews. Directional, with an explicit confidence level.
| Signal | Assessment |
|---|---|
| Maintenance | Active |
| Documentation | Adequate |
| License clarity | Clear |
| Deployment complexity | Low |
| DEV.co fit | Good |
| Assessment confidence | High |
Dynamic library loading via `--diff-plugin` poses native code execution risk; only load from trusted/verified sources. Command execution (`--shell`, monitored command, `--aftercommand`) must treat inputs as trusted to prevent injection attacks. No security audit or penetration test data published. PTY mode may leak terminal control sequences; review in security-sensitive environments.
Alternatives to consider
GNU watch
Standard Unix utility; no history, diff, or hooks. Suitable if monitoring without analysis required; hwatch is a superset.
Tmux/screen capture + tail
Manual session logging; no built-in diffing or triggers. Flexible but labor-intensive; hwatch automates the workflow.
Custom shell scripts + logging
Full control; no tool overhead. Requires development effort; hwatch provides ready-made solution with TUI and JSON output.
Build on hwatch with DEV.co software developers
Evaluate hwatch for your infrastructure automation and observability needs. Our team can advise on integration, security hardening, and deployment strategies for your environment.
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hwatch FAQ
Can hwatch run privileged commands safely?
Is hwatch suitable for production alerting?
What happens if the monitored command fails or hangs?
Can hwatch be run headless or in CI/CD without a TTY?
Custom software development services
From first prototype to production, DEV.co delivers software development services around tools like hwatch. Our software development agency staffs experienced software developers and web developers for custom software development, web development, integrations, and ongoing support across open-source observability and beyond.
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