Essential Bash Scripting Tips & Practical Linux Monitoring Scripts

Precautions

1) Add interpreter line: #!/bin/bash

2) Use four spaces for indentation and add comments.

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

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

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

6) Test scripts before production.

1. Generate Random String or Number

Example to get a random 8‑character string:

Example to get a random 8‑digit number:

Use cksum to print CRC checksum and byte count.

2. Define a Color Output Function

Define a function using the function keyword (optional).

3. Batch Create Users

4. Check If a Package Is Installed

5. Check Service Status

6. Check Host Liveness

Method 1: Put erroneous IPs in an array and consider ping failed after three attempts.

Method 2: Store failure count in FAIL_COUNT variable and exit after three failures.

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

7. Monitor CPU, Memory, and Disk Utilization

CPU: Use vmstat to analyze CPU statistics.

Memory:

Disk:

8. Batch Host Disk Utilization Monitoring

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

Create a configuration file listing each host’s IP, user, and port.

9. Check Website Availability

1) Verify URL reachability.

2) Test URL three times, similar to host liveness check.

These shell script examples are practical and often appear in interviews; practice writing them yourself rather than just copying.