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13_README.md

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Files and JSON in Go

This directory contains examples of working with files and JSON in Go.

JSON Overview

JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write and easy for machines to parse and generate. Go provides built-in support for JSON encoding and decoding through the encoding/json package.

Key Concepts

1. Marshaling and Unmarshaling

  • Marshaling: Converting Go data structures to JSON

    data, err := json.Marshal(value)

  • Unmarshaling: Converting JSON to Go data structures

    err := json.Unmarshal(jsonData, &value)

2. JSON Tags

Go uses struct tags to control how struct fields are encoded/decoded:

type Person struct {
    Name      string `json:"name"`              // Maps to "name" in JSON
    Age       int    `json:"age"`               // Maps to "age" in JSON
    Address   string `json:"address,omitempty"` // Omitted if empty
    SSN       string `json:"-"`                 // Ignored in JSON
}

3. Encoder and Decoder

For streaming JSON data (useful for large files):

// Encoding
encoder := json.NewEncoder(writer)
encoder.Encode(value)

// Decoding
decoder := json.NewDecoder(reader)
decoder.Decode(&value)

File Operations

Go provides several packages for file operations:

  • os: Basic file operations (create, open, read, write)
  • io: Interfaces for I/O operations
  • bufio: Buffered I/O for better performance

Common File Operations

// Reading a file
data, err := os.ReadFile("filename.txt")

// Writing to a file
err := os.WriteFile("filename.txt", data, 0644)

// Opening a file
file, err := os.Open("filename.txt")     // Read-only
file, err := os.Create("filename.txt")   // Create new file

Examples in this Directory

  1. Basic JSON Marshaling/Unmarshaling: Converting between Go data structures and JSON strings
  2. Reading JSON from Files: Loading JSON data from files into Go structures
  3. Writing JSON to Files: Saving Go structures as JSON in files
  4. JSON Streaming with Encoder/Decoder: Efficient handling of JSON data streams

How to Run

Execute the following command from this directory:

go run .

Further Reading