How to Use the strconv.AppendInt() Function in Golang

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Golang strconv.AppendInt() function is “used to append the string form of the integer i, as generated by FormatInt, to dst and returns the extended buffer”.

Syntax

func AppendInt(dst []byte, i int64, base int) []byte

Parameters

  1. dst: It is a byte array to append the integer value.
  2. i: It is the integer value to be appended.
  3. base: It is the base of the given integer value.

Return value

The AppendInt() function returns the extended buffer after appending the integer value i.

Example 1: Using strconv.AppendInt() function

package main

import (
  "fmt"
  "strconv"
)

func main() {
  num := int64(123456789)
  buf := make([]byte, 0, 10)

  buf = strconv.AppendInt(buf, num, 10)
  fmt.Println(string(buf))
}

Output

123456789

Example 2: Complex Program of strconv.AppendInt()

package main

import (
  "fmt"
  "os"
  "strconv"
)

func main() {
  // List of numbers to append
  numbers := []int64{10, 20, 30, 40, 50}

  // Open a new file
  file, err := os.Create("numbers.txt")
  if err != nil {
    fmt.Println(err)
    os.Exit(1)
  }

  // Ensure the file gets closed
  defer file.Close()

  // Buffer to hold our string
  buf := make([]byte, 0, 64)

  for _, num := range numbers {
    // Clear the buffer
    buf = buf[:0]
    // Append the integer as a string to the buffer
    buf = strconv.AppendInt(buf, num, 10)
    // Append a newline
    buf = append(buf, '\n')
    // Write the buffer to the file
    file.Write(buf)
  }

  fmt.Println("File written successfully")
}

Output

Complex Program of strconv.AppendInt()

Example 3: strconv.AppendInt() with different base

package main

import (
  "fmt"
  "strconv"
)

func main() {

  // Using AppendInt() function
  value_1 := []byte("int value(base 10): ")
  value_1 = strconv.AppendInt(value_1, 21, 11)

  fmt.Println(string(value_1))
  fmt.Println("Length: ", len(value_1))
  fmt.Println("Capacity: ", cap(value_1))

  value_2 := []byte("int value(base 16): ")
  value_2 = strconv.AppendInt(value_2, 19, 21)
 
  fmt.Println(string(value_2))
  fmt.Println("Length: ", len(value_2))
  fmt.Println("Capacity: ", cap(value_2))
}

Output

int value(base 10): 1a
Length: 22
Capacity: 48
int value(base 16): j
Length: 21
Capacity: 48

That’s it.

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