Essential Bash Scripting Tips and Practical Monitoring Scripts

Precautions

1) Start scripts with the interpreter line: #!/bin/bash 2) Use four spaces for indentation and add plenty of comments.

3) Naming conventions: uppercase for constants, lowercase for local variables, lowercase for functions, names should reflect their purpose.

4) Variables are global by default; use local inside functions to limit scope.

5) Two useful debugging commands: set -e to exit on non‑zero status, set -x to print each command as it runs.

6) Always test scripts before deploying to production.

1. Generate Random String or Number

Generate a random 8‑character string:

Generate a random 8‑digit number:

Use cksum to print CRC checksum and byte count.

2. Define a Color Output String Function

Use the function keyword to define a function, with or without the keyword.

3. Bulk Create Users

4. Check If Package Is Installed

5. Check Service Status

6. Check Host Liveness

Method 1: Store erroneous IPs in an array and consider the host down after three ping failures.

Method 2: Use a FAIL_COUNT variable to track consecutive failures.

Method 3: Use a for loop to break on a successful ping; otherwise report failure.

7. Monitor CPU, Memory, and Disk Utilization

CPU: Use vmstat to analyze CPU statistics.

Memory:

Disk:

8. Bulk Host Disk Utilization Monitoring

Prerequisite: SSH password‑less or key‑based login between monitoring and target hosts.

Write a configuration file containing SSH connection info in the format: IP User Port.

9. Check Website Availability

1) Verify URL accessibility.

2) Test URL availability three times, using the same logic as host liveness checks.

These shell script examples are practical, frequently appear in interview questions, and are best learned by writing them yourself rather than copying and pasting.