How to Use fmt.Printf in Go: Syntax and Examples

Use fmt.Printf in Go to print formatted text to the console. It takes a format string with verbs like %d for integers and %s for strings, followed by values to insert in place of those verbs.

Syntax

The basic syntax of fmt.Printf is:

fmt.Printf(format string, values...)

Here:

• format string: A string with placeholders (verbs) like %d, %s, %f that specify how to format the values.
• values...: One or more values that replace the placeholders in order.

go

fmt.Printf("Hello %s, you have %d new messages.\n", "Alice", 5)

Example

This example shows how to print a greeting with a name and a number using fmt.Printf. It demonstrates string and integer formatting.

go

package main

import "fmt"

func main() {
    name := "Alice"
    messages := 5
    fmt.Printf("Hello %s, you have %d new messages.\n", name, messages)
}

Output

Hello Alice, you have 5 new messages.

Common Pitfalls

Common mistakes when using fmt.Printf include:

• Not matching the number of verbs with the number of values, which causes runtime errors.
• Using the wrong verb for a value type, like %d for a string.
• Forgetting to add \n at the end of the format string, which keeps the cursor on the same line.

Example of wrong and right usage:

go

package main

import "fmt"

func main() {
    // Wrong: missing value for %d
    // fmt.Printf("Count: %d\n") // This causes an error

    // Wrong: wrong verb for string
    // fmt.Printf("Name: %d\n", "Bob") // This causes an error

    // Right:
    fmt.Printf("Count: %d\n", 10)
    fmt.Printf("Name: %s\n", "Bob")
}

Output

Count: 10
Name: Bob

Quick Reference

Verb	Description	Example
%d	Decimal integer	42
%s	String	"hello"
%f	Floating-point number	3.14
%t	Boolean	true
%v	Default format for any value	varies
%%	Literal percent sign	%

Key Takeaways

Use fmt.Printf with a format string and matching values to print formatted output.

Match verbs like %d and %s correctly to the value types to avoid errors.

Always include \n at the end of the format string to move to the next line.

Common verbs include %d for integers, %s for strings, and %f for floats.

fmt.Printf does not add a newline automatically; you must include it in the format string.