Real-Time Linux Network Traffic Monitor Script

Monitoring real-time network traffic is a common requirement in Linux system administration and DevOps operations. This article presents a lightweight Bash script that tracks incoming (RX) and outgoing (TX) traffic on a specified network interface by reading kernel statistics from /proc/net/dev.

The script calculates per-second bandwidth usage and automatically converts raw byte counts into human-readable units for clarity.

📡 Real-Time Network Traffic Monitoring Script

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The script continuously samples network interface counters once per second and displays live throughput statistics.

#!/bin/bash
# Set interface name (e.g., eno1, eth0, wlan0)
eth="eno1"

# Convert bytes to human-readable units
bytes_to_human() {
    local bytes=$1
    if (( bytes < 1024 )); then
        echo "${bytes}B"
    elif (( bytes < 1048576 )); then
        printf "%.2fKB" "$(bc <<< "scale=2; $bytes / 1024")"
    elif (( bytes < 1073741824 )); then
        printf "%.2fMB" "$(bc <<< "scale=2; $bytes / 1048576")"
    else
        printf "%.2fGB" "$(bc <<< "scale=2; $bytes / 1073741824")"
    fi
}

# Real-time monitoring loop
while true; do
    RXpre=$(grep "$eth:" /proc/net/dev | awk '{print $2}')
    TXpre=$(grep "$eth:" /proc/net/dev | awk '{print $10}')

    sleep 1

    RXnext=$(grep "$eth:" /proc/net/dev | awk '{print $2}')
    TXnext=$(grep "$eth:" /proc/net/dev | awk '{print $10}')

    RX=$((RXnext - RXpre))
    TX=$((TXnext - TXpre))

    RX_human=$(bytes_to_human $RX)
    TX_human=$(bytes_to_human $TX)

    clear
    echo -e "\t RX `date +%H:%M:%S` TX"
    echo -e "$eth \t $RX_human/s   $TX_human/s"
done

⚙️ Script Functionality Overview

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This script provides a live, terminal-based dashboard for network throughput on a single interface, making it useful for diagnostics, performance analysis, and troubleshooting.

Key characteristics include:

• Per-second refresh rate for real-time visibility
• Automatic unit scaling from bytes to KB, MB, or GB
• Minimal dependencies, using standard Linux tools and /proc

🧠 How It Works Internally

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1. Interface Selection The eth variable defines the network interface to monitor (for example, eno1, eth0, or wlan0).

2. Kernel Statistics Access Linux exposes cumulative network counters through /proc/net/dev, which tracks RX and TX bytes since system boot.

3. Rate Calculation The script samples counters, waits exactly one second, then samples again. The difference between samples represents bytes per second.

4. Human-Readable Formatting Since Bash lacks floating-point arithmetic, the bc utility is used to format bandwidth values accurately.

🚀 How to Use the Script

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1. Create the script file

nano monitor_traffic.sh

2. Paste the script Ensure the eth variable matches your network interface. You can list interfaces with:

ip link

3. Make it executable

chmod +x monitor_traffic.sh

4. Run

./monitor_traffic.sh

5. Exit Press Ctrl+C to stop monitoring.

This approach offers a transparent and efficient alternative to heavier monitoring tools, making it ideal for quick diagnostics, embedded systems, or minimal server environments.