golang tutorials

How To Format a String in Golang

in this post, we’ll show you how to format strings in Golang. Golang has a large number of string formatting options. The fmt is a golang package that can be used to format a string. This package has inbuilt find functions that implement formatted I/O.

To format strings in Go, we use the following functions:

fmt.Printf
fmt.Sprintf
fmt.Fscanf

What’s fmt Package

The fmt package enables you to convert strings, numbers, and even objects to a particular string format. All of the formatting methods are parts of this package.

Format String Argument

d – decimal integer
o – octal integer
O – octal integer with 0o prefix
b – binary integer
x – hexadecimal integer lowercase
X – hexadecimal integer uppercase
f – decimal floating point, lowercase
F – decimal floating point, uppercase
e – scientific notation (mantissa/exponent), lowercase
E – scientific notation (mantissa/exponent), uppercase
g – the shortest representation of %e or %f
G – the shortest representation of %E or %F
c – a character represented by the corresponding Unicode code point
q – a quoted character
U – Unicode escape sequence
t – the word true or false
s – a string
v – default format
#v – Go-syntax representation of the value
T – a Go-syntax representation of the type of the value
p – pointer address
% – a double %% prints a single %

Go String Format Example

The fmt package provides a wide variety of string formatting functionalities. The formating method will format the string according to the specified format specifiers. Let’s look at a few popular string formatting examples in GoLang.

Format String Using Printf()

The fmt.Printf() method prints a formatted string to the console. The %s expects a string value and the %d an integer value.

Example:

package main

import (
    "fmt"
)

func main() {
    emp_name := "Rachel"
    age := 17
 salary := 123

    fmt.Printf("My name is %s, and I am %d years old. My annual wage is %d dollars\n", emp_name, age, salary)
}

Output :

My name is Rachel, and I am 17 years old. My annual wage is 123 dollars

Format String Using Sprintf()

The fmt.Sprintf function formats a string into a variable.

Example:

package main

import (
    "fmt"
)

func main() {
    emp_name := "Rachel"
    age := 17
 salary := 123
 formatted_str := fmt.Sprintf("My name is %s, and I am %d years old. My annual wage is %d dollars\n", emp_name, age, salary)

    fmt.Println(formatted_str)
}

Output :

My name is Rachel, and I am 17 years old. My annual wage is 123 dollars

Formatted String using Fscanf() Method

The Go language’s fmt.Fscanf() method scans the supplied text, reads from r, and then stores the space-separated values into subsequent arguments according to the format.

Syntax:

func Fscanf(r io.Reader, format string, a …interface{}) (n int, err error)

It returns the number of items successfully parsed. The above function accepts three parameters:

r io.Reader: The scanned specified texts are stored in this parameter.
format string: This option specifies the various formats in which the elements should be received.
a …interface: This is the variable that is specified for each element.

Example:

package main

import (
    "fmt"
    "os"
    "strings"
)

func main() {
    var (
        emp_name string
        age int
        salary int
    )
      
    r := strings.NewReader("Rachel 23 123")
 
    emp, err := fmt.Fscanf(r, "%s %d %d", &emp_name, &age, &salary)

    if err != nil {
        fmt.Fprintf(os.Stderr, "Fscanf: %v\n", err)
    }

    fmt.Println(emp_name, age, salary)
      
    fmt.Println(emp)
}

Output :