name	description
frate	Monitor file growth rate with EMA smoothing. Use when you need to watch how fast a file is growing.

frate

Monitor how fast a file is growing. Prints file size and EMA-smoothed growth rates over 10s, 1m, and 5m windows.

Install

go install github.com/hayeah/frate@latest

Usage

frate <file>

Polls every 5 seconds, one line per update to stderr.

Output format:

<size>   10s <rate>   1m <rate>   5m <rate>

Examples

# Watch a log file grow
frate /var/log/app.log

# Monitor a database dump in progress
pg_dump mydb > dump.sql & frate dump.sql

# Track a large download
frate ~/Downloads/bigfile.zip

# Pipe-friendly: frate writes to stderr, so stdout is free
frate data.csv 2>rate.log

Output

12.3 MB   10s 1.5 MB/s    1m 1.2 MB/s     5m 1.1 MB/s
14.1 MB   10s 1.4 MB/s    1m 1.3 MB/s     5m 1.1 MB/s

• 10s — reacts quickly to rate changes
• 1m — smoothed over ~1 minute
• 5m — long-term trend

All rates use time-based EMA: alpha = 1 - exp(-dt/window). This adapts correctly regardless of actual polling jitter.

Quirks

• Output goes to stderr, not stdout.
• When the file isn't growing, all rates decay toward 0 B/s (they don't snap to zero instantly — that's the EMA smoothing).
• If the file shrinks (e.g. truncation), the rate goes negative.
• No external dependencies — just Go stdlib.