Let’s break down what this script does in detail. The script is named user_accounts_info.sh, authored by GJS (homelab-alpha), and its purpose is to retrieve and organize information about system user accounts. It categorizes the accounts into system and normal user categories and displays relevant details in a formatted manner.

Here’s a detailed explanation:

Script Metadata

  • Filename: user_accounts_info.sh
  • Author: GJS (homelab-alpha)
  • Date: May 18, 2024
  • Version: 1.0.1
  • Description: The script retrieves information about system user accounts and organizes them into system and normal user categories.
  • RAW Script: user_accounts_info.sh

Overview

The script is designed to extract user account information from the system’s passwd file and categorize them into system and normal users based on UID and GID values defined in the login.defs file. It uses awk for data processing and displays the information in a tabular format.


Functions

This function prints a formatted header for the output. It uses echo and printf to create a table-like header.

print_header() {
  echo "==========================================================================================================="
  printf "%-15s %-15s %-30s %-25s %-20s\n" "UID" "GID" "Shell" "Username" "Groups"
  echo "==========================================================================================================="
}

Main Program

File Paths

The script defines the paths to the login.defs and passwd files.

login_defs="/etc/login.defs"
passwd_file="/etc/passwd"

File Existence Check

It checks if the required files (login.defs and passwd) exist. If either file is missing, the script exits with an error message.

if [ ! -f "$login_defs" ] || [ ! -f "$passwd_file" ]; then
  echo "ERROR: Required files not found."
  exit 1
fi

Retrieve UID and GID Limits

The script extracts the minimum and maximum UID and GID values from the login.defs file using awk.

min_uid=$(awk '/^UID_MIN/{print $2}' "$login_defs")
max_uid=$(awk '/^UID_MAX/{print $2}' "$login_defs")
min_gid=$(awk '/^GID_MIN/{print $2}' "$login_defs")
max_gid=$(awk '/^GID_MAX/{print $2}' "$login_defs")

Check for awk Availability

It verifies if awk is available on the system. If not, the script exits with an error message.

if ! command -v awk &>/dev/null; then
  echo "ERROR: awk command not found."
  exit 1
fi

The script prints the header for system user accounts and then uses awk to process the passwd file. It filters out accounts that fall outside the range of normal user UIDs and GIDs, displaying only system accounts. It also retrieves and displays the groups for each user.

print_header "System User Accounts"
awk -F':' -v "min_uid=$min_uid" -v "max_uid=$max_uid" -v "min_gid=$min_gid" -v "max_gid=$max_gid" '
    function get_user_groups(username) {
        "id -Gn " username | getline groups
        close("id -Gn " username)
        return groups
    }
    !($3 >= min_uid && $3 <= max_uid && $4 >= min_gid && $4 <= max_gid) {
        printf "%-15s %-15s %-30s %-25s %-20s\n", "UID: "$3, "GID: "$4, "Shell: "$7, $1, get_user_groups($1)
    }' "$passwd_file" | sort -n -t ':' -k 2

Similarly, the script prints the header for normal user accounts and uses awk to process and display details for users within the specified UID and GID ranges.

echo "" # Add a blank line between sections

print_header "Normal User Accounts"
awk -F':' -v "min_uid=$min_uid" -v "max_uid=$max_uid" -v "min_gid=$min_gid" -v "max_gid=$max_gid" '
    function get_user_groups(username) {
        "id -Gn " username | getline groups
        close("id -Gn " username)
        return groups
    }
    $3 >= min_uid && $3 <= max_uid && $4 >= min_gid && $4 <= max_gid {
        printf "%-15s %-15s %-30s %-25s %-20s\n", "UID: "$3, "GID: "$4, "Shell: "$7, $1, get_user_groups($1)
    }' "$passwd_file" | sort -n -t ':' -k 2

Notes

  • The script requires read access to the /etc/login.defs and /etc/passwd files.
  • It relies on awk for data processing.
  • The output is sorted based on UID and GID for easier readability.

This script effectively categorizes and displays user account information on a Unix-like system, providing a clear separation between system and normal users.

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Last updated 22 Sep 2024, 12:15 CEST . history