💀 I built a full system monitor in Bash — and fought awk along the way

November 4, 2025

This content originally appeared on DEV Community and was authored by DanLin

I wanted to see how far I could push pure Bash before it collapses under its own syntax.
So, naturally, I decided to write a system monitoring tool — in Bash.
And thus, system-monitor was born:
GitHub repo

Yes, it’s fully functional. Yes, it uses colors. Yes, awk is involved.

No, I don’t recommend doing this sober.

The idea

I wanted a single script that could show:

CPU load and number of cores
RAM usage and percentage
Disk space for /
Network I/O
Process count Basically, the “lazy Linux admin toolkit” in one file. Something like this:

./system-monitor.sh

and boom — everything you’d usually get from top, free, df, and ip combined.

The features

What started as a 10-line script turned into a 250+ line CLI tool with:

Command-line arguments (–help, –brief, –no-color, –version, -i N)
Colorized output for warnings/critical thresholds
Continuous monitoring mode
Safe shutdown with signal trapping (Ctrl+C)
Brief (machine-readable) mode for piping into other scripts
Dependency checks and graceful error handling

Example:

./system-monitor.sh -i 5 --no-color

Updates every 5 seconds without colors.
Press Ctrl+C to stop — yes, it even says goodbye politely.

Some code highlights

Color management:

RED='\033[0;31m'
YELLOW='\033[1;33m'
GREEN='\033[0;32m'
NC='\033[0m'

Because monitoring your system is serious business — but who doesn’t love a bit of RGB?

Load detection magic:

CPU_LOAD_1MIN=$(cat /proc/loadavg | awk '{print $1}')
CPU_CORES=$(nproc)
load_percent=$(echo "scale=0; ($CPU_LOAD_1MIN * 100) / $CPU_CORES" | bc)

That moment when you realize you’re using awk, bc, and /proc in one line and it actually works.

Network metrics:

interface=$(ip route get 8.8.8.8 | awk '{print $5}' | head -1)
rx=$(cat /sys/class/net/$interface/statistics/rx_bytes)
tx=$(cat /sys/class/net/$interface/statistics/tx_bytes)

I like to imagine Bash crying softly every time it runs this.

What I learned

Bash can do a lot — if you’re patient (and slightly masochistic).
Quoting is a survival skill. Forget one and you’re debugging for hours.
awk is an ancient curse. It always works, but never for the reason you expect.
Color helps debugging. Visual feedback saves your sanity.
Document your code. Because 3 a.m. you will have no clue what that $7 in awk '{print $7}' was.

The brief mode

I added a --brief flag that outputs all metrics in a machine-readable format — perfect for logging or Prometheus-style integration.

./system-monitor.sh --brief

Output:

timestamp=1730765432
cpu_load_percent=12
mem_usage_percent=43.5
disk_usage_percent=56
network_rx_mb=12.4
process_count=187

Basically, JSON for people who hate themselves.

Safety first: signal handling

If you hit Ctrl+C, it doesn’t just die — it politely says goodbye:

trap cleanup INT TERM

cleanup() {
    echo -e "\nMonitoring stopped. Goodbye!"
    exit 0
}

Because professionalism.

AUR packaging

After testing it on Arch, I thought — why not go all in?
So I wrote a PKGBUILD, threw it into the AUR, and now you can literally install it with:

yay -S system-monitor

And that’s the moment I realized:

“Oh no. I’ve become that guy who writes Bash utilities for other people.”

Final thoughts

Was this efficient? Probably not.
Did I learn a lot? Absolutely.

Here’s what I got from it:

Deep understanding of Bash syntax and traps
Practical use of /proc and awk
Appreciation for proper CLI design
And a newfound respect for people who don’t do this in Bash

If you’re thinking of writing your first utility — do it.
Even if it’s messy. Even if awk haunts your dreams.

Because once you see your tool working, it’s worth every headache.

Links

GitHub: https://github.com/DanLinX2004X/system-monitor

AUR: https://aur.archlinux.org/packages/system-monitor

This content originally appeared on DEV Community and was authored by DanLin