Exploring the datacheck Bash Script: Network Data Monitoring

Exploring the datacheck Bash Script: Network Data Monitoring

In this article, we'll explore the purpose, structure, and functionality of a Bash script called datacheck. This script is designed to monitor network statistics using vnstat, a popular network traffic monitoring tool, and provides flexibility in how the data is presented.

Purpose of the Script

The primary purpose of the datacheck script is to retrieve and display network data usage for specified network interfaces. It provides an easy way to monitor traffic over various time periods (daily, monthly, yearly, or for a custom number of days) across different network interfaces on the system.

Functions and Features

Let's break down the core functionality of the script and see how each section works.

1. Setting the Default Interface

The script begins by defining a default network interface:

default_interface="enp0s25"

This default interface is enp0s25, which can be replaced or extended to include additional network interfaces, depending on user input.

2. Help Message Display

One of the essential parts of a command-line tool is to provide help or usage information to the user. This script includes a display_help function that outputs the usage details:

display_help() {
  echo "Usage: $0 [OPTION] [DAYS]"
  echo "Options:"
  echo "  -m: Display monthly statistics"
  echo "  -d: Display daily statistics"
  echo "  -y: Display yearly statistics"
  echo "  -t <DAYS>: Display statistics for the last <DAYS> days"
  echo "  -a: Show data for all interfaces"
  echo "  -h: Display this help message"
}

The user can access this help message by running the script with the -h option, which makes it clear what options are available and how to use the script.

3. Parsing User Input

The script uses the getopts command to parse command-line options:

while getopts ":mdyht:a" opt; do
  case ${opt} in
    m ) option="-m" ;;
    d ) option="-d" ;;
    y ) option="-y" ;;
    t ) days=$OPTARG ;;
    a ) all_interfaces=true ;;
    h ) display_help; exit 0 ;;
    \? ) echo "Invalid option: $OPTARG"; display_help; exit 1 ;;
  esac
done

This allows the script to handle different arguments, such as:

4. Handling All Interfaces

If the user specifies the -a option, the script adjusts to retrieve data for all available network interfaces:

ifaces=$(ls /sys/class/net | grep -v lo)
interfaces="${ifaces[@]}"

This command lists all network interfaces in the system, excluding the lo (loopback) interface, and assigns them to the interfaces variable. The script will then loop through each interface, retrieving its statistics.

5. Handling Custom Time Periods

If the user specifies a custom number of days using the -t option, the script modifies the vnstat command accordingly:

if [ -n "$days" ]; then
  option+="-t $days"
fi

This allows the script to execute a vnstat query for the last <DAYS> days, giving more granular control over the time period for which data is displayed.

6. Running vnstat and Handling Output

The script loops through each specified network interface and runs the vnstat command:

for interface in $interfaces; do
  vnstat_output=$(vnstat -i "$interface" $option 2>&1)

Here, it captures the output of the vnstat command, which retrieves traffic data for the specified interface and time period.

The script checks if the vnstat command returns any errors:

if [[ "$vnstat_output" == *"Error"* ]]; then
  no_data_interfaces+=("$interface")
else
  echo "Interface: $interface"
  echo "$vnstat_output"
fi

If vnstat fails (e.g., no data available for a particular interface), the interface is added to the no_data_interfaces array. Otherwise, it prints the output for that interface.

7. Displaying Interfaces with No Data

Finally, if there are any interfaces for which no data is available, the script informs the user:

if [ ${#no_data_interfaces[@]} -gt 0 ]; then
  echo "No data available for the following interfaces: ${no_data_interfaces[@]}"
fi

This ensures the user is aware of any issues with specific interfaces.

8. Example Output for usage:*

Interface: enp0s25
Database updated: 2024-09-20 14:00:00

   enp0s25 since 2024-04-15

          rx:  20.52 TiB      tx:  8.25 TiB      total:  28.78 TiB

   monthly
                     rx      |     tx      |    total    |   avg. rate
     ------------------------+-------------+-------------+---------------
       2024-08      2.62 TiB |    1.58 TiB |    4.20 TiB |   13.80 Mbit/s
       2024-09      2.09 TiB |  902.77 GiB |    2.98 TiB |   15.47 Mbit/s
     ------------------------+-------------+-------------+---------------
     estimated      3.21 TiB |    1.35 TiB |    4.56 TiB |

   daily
                     rx      |     tx      |    total    |   avg. rate
     ------------------------+-------------+-------------+---------------
     yesterday     72.81 GiB |   35.78 GiB |  108.59 GiB |   10.80 Mbit/s
         today     22.34 GiB |   14.42 GiB |   36.76 GiB |    6.27 Mbit/s
     ------------------------+-------------+-------------+---------------
     estimated     38.30 GiB |   24.72 GiB |   63.02 GiB |

Summary

The datacheck script is a powerful tool for monitoring network usage across different time periods and interfaces. It provides flexibility with options for displaying daily, monthly, yearly, or custom time-frame data, and can be extended to monitor all interfaces on the system. Here's a quick recap of the script's key features:

This script serves as an efficient solution for system administrators or users needing to monitor network traffic usage quickly and easily across various interfaces.