[Dev] fmt.Println, fmt.Fprintf, fmt.Sprintf in Go Language (Golang)

Contents

When should I use it?

Question 1: “Am I just printing something for a human?”

YES → use fmt.Println

fmt.Println("Hi,", name, age)

Use this for:

• debugging
• CLI output
• quick logs
• learning

Rule: if you don’t care about exact formatting → Println.

JS equivalent:

console.log("Hi", name, age)

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Question 2: “Do I need a formatted string or to write somewhere specific?”

YES → use fmt.Fprintf or fmt.Sprintf

A) Writing somewhere (HTTP, file, buffer)

➡ fmt.Fprintf

fmt.Fprintf(w, "Hi %s, age %d\n", name, age)

Think:

“formatted print to something”

JS equivalent:

res.write(`Hi ${name}, age ${age}`)

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B) Need the string value

➡ fmt.Sprintf

msg := fmt.Sprintf("Hi %s, age %d", name, age)

Think:

“string printf”

JS equivalent:

const msg = `Hi ${name}, age ${age}`

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TLDR

You can survive your entire Go job knowing only:

• Println
• Sprintf
• Fprintf

Final mental hack (remember this)

P = Print

F = Format

S = String

• Println → prints
• Sprintf → string
• Fprintf → formatted output