Standard Library
fmt

fmt package

The fmt package implements I/O formatting following the example of C's printf and scanf.

docs (opens in a new tab)

How to use fmt package?

The following code snippet contains some examples of using fmt functions, which you can try here (opens in a new tab).

package main
 
import (
	"fmt"
)
 
func main() {
	// Println writes to standard output.
	fmt.Println("Follow The Pattern")   // Follow The Pattern
	fmt.Println("Follow", 0, "Pattern") // Follow 0 Pattern
 
	fmt.Print("Follow The Pattern") // Prints to standard output without newline
	fmt.Print(" Follow The Pattern\n")
 
	localStruct := struct {
		Count int
		Title string
	}{1, "FP"}
 
	fmt.Printf("Integer: %d, String: %s, type of literal: %T, Value: %v, Struct type: %T \n",
		1, "hello", int64(1), localStruct, localStruct)
	// Integer: 1, String: hello, type of literal: int64, Value: {1 FP}, Struct type: struct { Count int; Title string } ß
 
	// prints literal percent sign, consume no value
	fmt.Printf("Percent sign: %%\n") // %
 
	the := 0
	text := fmt.Sprint("Follow", the, "Pattern") // stores the string into variable, without white space
	fmt.Println(text)                            // Follow0Pattern
 
	text = fmt.Sprintf("Integer: %d, String: %s, Value type: %T, Value: %v", 1, "hello", int64(1), localStruct)
	fmt.Println(text) // Integer: 1, String: hello, Value type: int64, Value: {1 FP}
}

Using fmt package with packages that implements io.Writer interface

The os.File type implements the io.Writer interface, allowing it to be used together with fmt functions. It will behave the same way as if you were writing to the console.

package main
 
import (
	"fmt"
	"log"
	"os"
)
 
func main() {
	localStruct := struct {
		Count int
		Title string
	}{1, "FP"}
 
	// fmt.Fprint can print to any interface that implements io.Writer like os.File
	file, err := os.Create("./dump.txt")
	if err != nil {
		log.Fatal(err) // exit from the application while it prints the error
	}
 
	fmt.Fprintln(file, "Follow The Pattern")
	fmt.Fprintln(file, "Follow", 0, "Pattern")
	fmt.Fprintf(file, "Integer: %d, String: %s, type of literal: %T, Value: %v, Struct Type: %T \n",
		1, "hello", int64(1), localStruct, localStruct)
 
	// File content
	/*
		Follow The Pattern
		Follow 0 Pattern
		Integer: 1, String: hello, type of literal: int64, Value: {1 FP}, Struct Type: struct { Count int; Title string }
 
	*/
 
	err = file.Close()
	if err != nil {
		log.Fatal(err)
	}
}

You can run the code in your browser here (opens in a new tab).

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