system-monitor (Zig port)

A from-scratch Zig reimplementation of the Rust system-monitor TUI. Zig has no equivalent of sysinfo, ratatui/crossterm, tokio, or serde+toml, so this isn't a syntax transliteration — the OS-facing pieces are rewritten against Linux's /proc filesystem and raw terminal control directly.

Requirements

• Zig 0.14.x (built and tested against 0.14.1 specifically).
• Linux. All system-data collection goes through /proc; there's no macOS or Windows backend. Porting further would mean adding sysctl-based collectors for macOS and WMI/PDH-based ones for Windows — a genuinely separate effort, not a small tweak.

Why pin to 0.14.x instead of the latest Zig?

The current stable release, 0.16.0 (April 2026), shipped a sweeping rewrite ("I/O as an Interface") that threads an Io instance through essentially every file, process, and even random-number operation, on top of 0.15's earlier std.io.Writer/Reader overhaul ("Writergate"). Both are recent enough, and large enough, that I couldn't write against them reliably without a compiler to check my work against — even Zig's own release notes describe parts of the new interface as experimental. 0.14.1 is the last release before that rewrite: stable, thoroughly documented, and what most existing Zig code and tutorials still target. If you want this on 0.16+, the diff is substantial (Io params on most calls in term.zig, config.zig, and the collectors) — happy to help with that migration as a separate pass if you'd like it.

Build & run

zig build run

or build then run separately:

zig build
./zig-out/bin/system-monitor

Press q or Esc to quit, ↑/↓ to move the process selection, PgUp/PgDn to jump by 10.

What I actually verified

I don't have a way to hand you code I merely believe compiles — I got a real Zig 0.14.1 toolchain running in my sandbox (the ziglang PyPI package, which bundles official release binaries) and used it:

• zig build succeeds with no errors or warnings.
• Every collector ran against this sandbox's real /proc and returned sane values — including watching CPU% correctly jump to ~100% and a yes process correctly rise to the top of the process table when I ran one as a synthetic load, which confirms the delta-based CPU sampling (see below) is actually computing the right thing, not just compiling.
• The full interactive binary ran end-to-end attached to a real pseudo-terminal (Python's pty module): raw mode, alternate screen, colors, the Unicode gauge/box characters, the process table, three ticks at the correct ~1-second cadence, q correctly quitting, and the terminal being cleanly restored afterward (cursor shown, alternate screen exited) — all confirmed from the captured raw output.
• The config file load → edit → reload round-trip was tested directly, including comment lines.

term.zig (raw mode, polling, ioctl for terminal size) is the one file most dependent on exact OS/libc behavior rather than pure logic — it's kept isolated so if anything ever needs adjusting on a different machine, the change stays contained to that one file.

Layout

build.zig
src/
  main.zig              entry point, tick/input loop
  models.zig             data structs (→ models.rs)
  utils.zig               byte/percent formatting (→ utils.rs)
  controller.zig          process-list scroll state (→ controller.rs)
  config.zig               settings load/save (→ config/mod.rs)
  term.zig                  raw mode, alt screen, key polling (→ crossterm)
  ui.zig                    frame rendering (→ ui/mod.rs, ratatui)
  collector/
    collector.zig            aggregates the sub-collectors (→ collector/mod.rs)
    cpu.zig, memory.zig, disk.zig, network.zig, process.zig

Rust → Zig mapping

Rust crate / file	Zig approach
sysinfo	Direct /proc parsing: /proc/stat, /proc/meminfo, /proc/net/dev, /proc/[pid]/{stat,comm,status}. Disk space shells out to df -P -k (see disk.zig for why, not a syscall).
ratatui + crossterm	term.zig (raw std.posix termios/poll/ioctl) + ui.zig (hand-written ANSI rendering — text gauges instead of ratatui's bordered-box widgets).
tokio	None needed. The original's tokio::select! between a tick and a 10ms input-poll sleep becomes a plain loop in main.zig that checks elapsed time each iteration — same two branches, sequenced instead of raced.
serde + toml	A small hand-rolled parser/writer in config.zig for the two known fields. The file it writes is still valid basic TOML.
anyhow / thiserror	Zig's built-in error unions; no crate needed.

Deliberate deviations from the original

I kept this a faithful port by default, but flagged (rather than silently fixed) a couple of things:

• process_limit is actually used. In the Rust version, config.rs defines process_limit (default 15) but ui/mod.rs's render_processes hardcodes .take(15) instead of reading it — the setting was loaded but never wired up. ui.zig reads it from Settings. Since the default is also 15, behavior is identical unless you actually change the setting. If you want to match the original's hardcoded-15 exactly, pass 15 instead of settings.process_limit in main.zig.
• CPU sampling no longer blocks. The original's cpu.rs sleeps 200ms inside every collect() call to get two samples far enough apart (that's how sysinfo's refresh works). cpu.zig instead keeps the previous /proc/stat sample across ticks and diffs against it each time — the same technique top/htop use — so collection never blocks. Only visible effect: CPU% reads 0% on the very first frame instead of after a 200ms delay.
• Disk targets / explicitly. The original takes whatever disk sysinfo happens to enumerate first, which depends on OS-reported ordering. disk.zig targets the root filesystem by name instead — change DiskCollector.mount_point if you want a different one.

Everything else — including things I didn't fix, like network stats being collected but never shown in the UI, and Ctrl+C not quitting the app because raw mode disables ISIG and nothing handles it explicitly — matches the original on purpose.

Config file

$XDG_CONFIG_HOME/system-monitor/config.toml, falling back to $HOME/.config/system-monitor/config.toml — same location logic as the original's dirs::config_dir() on Linux. Created with defaults (update_ms = 1000, process_limit = 15) on first run if missing.