JIYIK CN >

The Go language provides a lot of file manipulation tools, one of which is how to read files into strings. ioutil.ReadFile(), File.Read(), buf.ReadFrom()and strings.Builder are just a few of the methods that can be used to efficiently write file contents to strings.

Using ioutil.ReadFile() method in Go

package main

import
(
    "fmt"

    "io/ioutil"
)

func main() {

    inputData := []byte("Hello, World!")

    err := ioutil.WriteFile("File.txt", inputData, 0777)

    Data, err := ioutil.ReadFile("File.txt")

    if err != nil {

        fmt.Println(err)
    }

    fmt.Print(string(Data))

}

Output:

Hello, World!

The above code allows us to create a new file and write data to it. We then use the ioutil.ReadFile() method to read the created file.

Using File.Read() method in Go

package main

import (
    "fmt"

    "io/ioutil"

    "log"

    "os"

    "io"
)

func main() {

    inputData := []byte("Hello, World!")

    err := ioutil.WriteFile("file.txt", inputData, 0777)

    f, err := os.Open("file.txt")

    if err != nil {
        log.Fatalf("Error in reading file: %v", err)
    }

    defer f.Close()

    buf := make([]byte, 1024)

    for {
        n, err := f.Read(buf)

    if err == io.EOF {

        break
    }
    if err != nil {

        fmt.Println(err)

        continue
    }
    if n > 0 {

        fmt.Println(string(buf[:n]))
    }
    }
}

Output:

Hello, World!

In the code above, we read the file by splitting it. We specify the buffer size to read each time and then allocate only len(buf) in memory.

The file is then read in segments with each iteration. This method is mainly used for large files where the contents of the file cannot fit completely into memory.

Using buf.ReadFrom() method in Go

package main

import (
  "fmt"

  "io/ioutil"

  "os"

  "bytes"

  "log"
)

func main() {
    inputData := []byte("Hello, World!")

    err := ioutil.WriteFile("File.txt", inputData, 0777)

   f, err := os.Open("File.txt")

   if err != nil{

     log.Fatal(err)
   }
   defer f.Close()

   buf := new(bytes.Buffer)

   buf.ReadFrom(f)

   data := buf.String()

   fmt.Print(data)

}

Output:

Hello, World!

In the above code, we have used buf.ReadFrom()readData from the file until EOF and appended it to a buffer; the buffer size grows as needed.

Using strings.Builder methods in Go

package main

import (
    "io/ioutil"

   "io"

   "os"

   "strings"
)

func main() {
    inputData := []byte("Hello, World!")

    err := ioutil.WriteFile("file.txt", inputData, 0777)

   f, err := os.Open("file.txt")

   if err != nil {

      panic(err)
   }

   defer f.Close()

   b := new(strings.Builder)

   io.Copy(b, f)

   print(b.String())
}

Output:

Hello, World!

In the above code, strings.Builder concatenates the strings. The data is read from the file one by one and then printed together.