Overview

Today I transitioned from interactive CLI programs to data-driven applications.

Instead of relying on terminal input, the program reads structured data from a file, processes it, and writes results back to disk. This is a foundational pattern for backend services and data processing tools.

What I Built

A Student Data Processor that:

• reads student records from a file (students.txt)
• parses each line into a Student struct
• computes aggregate metrics (average score)
• finds top-performing students (supports ties)
• writes results to an output file (result.txt)
• handles errors at every step

Input Format

students.txt:

Alice 20 85 Bob 22 70 Charlie 19 95

Each line:

Name Age Score

Core Data Model

type Student struct { Name string Age int Score int }

Key Implementation Patterns

Open file safely

file, err := os.Open(“students.txt”) if err != nil { return nil, err } defer file.Close()

Read line-by-line

scanner := bufio.NewScanner(file)

for scanner.Scan() { line := scanner.Text() }

Check scanner errors

if err := scanner.Err(); err != nil { return nil, err }

Parse structured data

var s Student _, err := fmt.Sscanf(line, “%s %d %d”, &s.Name, &s.Age, &s.Score)

Skip invalid lines

student, err := stringToStudent(line) if err != nil { fmt.Println(“Skipping invalid line:”, line) continue }

Write results

output := fmt.Sprintf(“Average Score: %.2f ”, avg) os.WriteFile(“result.txt”, []byte(output), 0644)

Example Output

Average Score: 83.33 Top Student: Charlie (95)

Key Takeaways

• File I/O enables real-world data processing
• bufio.Scanner is standard for reading files
• Always defer file.Close()
• Always check scanner.Err()
• Convert raw input into structs
• Prefer robustness over crashing

Reflection

This exercise introduced a common backend pattern:

Input → Parse → Process → Output

This is widely used in backend systems and data pipelines.

Next Steps

• Organize code into packages (Day 13)
• Improve validation
• Build a small multi-file project