Go Printing to Stdout and Stderr

Internal

• Go Language
• Go Code Examples
• The fmt Package

Bootstrapping Functions

Both print() and println() are pre-declared functions, ready to use without any import.

TODO: https://golang.org/ref/spec#Bootstrapping

println()

func main() {
  println("something")
}

fmt Functions

fmt.Printf()

https://golang.org/pkg/fmt/#Printf

import "fmt"

// ...
fmt.Printf("something %s", "blue")

Print() expects a format specifier (or a format string) as the first argument, which contains conversion characters (ex. %s):

%v

%v renders the value in a default format. When printing structs, the plus flag %+v adds field names.

%#v renders a Go-syntax representation of the value.

%T

%T renders a Go-syntax representation of the type of the value.

Strings

color := "blue"
fmt.Printf("The color is %s\n", color)

Integers

size := 1
fmt.Printf("The size is %d\n", size)

Characters

c := 'x'
fmt.Printf("The character is %c\n", c)

Booleans

b := true
fmt.Printf("The boolean value is %t\n", b)

Floating Point Numbers

f := 1.0
fmt.Printf("The floating point value is %f\n", f)

Pointers

s := "something"
sPtr := &s
fmt.Printf("pointer value: %p\n", sPtr)

"%p" prepend the "0x" prefix.

Pointers can be also represented using "%X" (base 16, upper case characters).

Structs

Go Structs | Printing Structs