Master Bash Scripting: Tips and Ready‑to‑Use Monitoring Scripts

Precautions

1) Add the interpreter line #!/bin/bash at the top of every script.

2) Use four spaces for indentation and add ample comments.

3) Naming convention: global variables in uppercase, local variables and functions in lowercase, and names should reflect their purpose.

4) Variables are global by default; declare local inside functions to avoid scope pollution.

5) Two useful debugging commands: set -e to exit on non‑zero status, and set -x to trace command execution.

6) Always test scripts thoroughly before deploying to production.

1. Generate Random Strings or Numbers

Random 8‑character string:

Random 8‑digit number:

Use cksum to print CRC checksum and byte count.

2. Define a Color‑Output Function

Use the function keyword (optional) to create a function that prints colored text.

3. Bulk Create Users

4. Check If a Package Is Installed

5. Verify Service Status

6. Check Host Liveness

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

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

Method 3: Loop with for; break on a successful ping, otherwise report failure after the loop.

7. Monitor CPU, Memory, and Disk Utilization

CPU: Use vmstat to analyze CPU statistics.

Memory:

Disk:

8. Bulk Host Disk Utilization Monitoring

Prerequisite: password‑less SSH (key‑based) between monitoring and target hosts.

Maintain a configuration file listing each host’s IP User Port information.

9. Verify Website Availability

1) Check URL reachability

2) Perform three consecutive checks – the logic mirrors the host‑liveness checks described earlier.

These Bash script examples are practical, frequently appear in technical interviews, and are intended for hands‑on practice rather than copy‑paste execution.