Essential Bash Scripting Practices for Linux Operations and Monitoring

Precautions

1) Add 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, and names should reflect their purpose.

4) Variables are global by default; use local inside functions to avoid polluting other scopes.

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

6) Always test scripts before deploying to production.

1. Generate Random String or Number

Random 8‑character string:

Random 8‑digit number:

cksum prints CRC checksum and byte count.

2. Define a Color Output Function

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

3. Batch Create Users

4. Check If a Package Is Installed

5. Check Service Status

6. Check Host Liveness

Method 1: Put erroneous IPs into an array and consider a host down after three ping failures.

Method 2: Store failure count in a variable FAIL_COUNT and treat three consecutive failures as down.

Method 3: Use a for loop that breaks on a successful ping; otherwise print ping failure.

7. Monitor CPU, Memory, and Disk Utilization

CPU – use vmstat to analyze CPU statistics.

Memory – (image shows memory usage).

Disk – (image shows disk usage).

8. Batch Host Disk Utilization Monitoring

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

Create a configuration file that stores SSH connection info in the format: IP User Port.

9. Check Website Availability

1) Verify URL reachability.

2) Test URL three times; the logic mirrors the host‑liveness checks above.

These practical Bash script examples are frequently asked in interviews; hands‑on practice is essential for mastery.