The common way to read files in GO language

This article illustrates the common file reading methods in the GO language. Share with you for your reference. The specific analysis is as follows:

Golang has many ways to read files, so I don't know how to choose when I just started, so I post it here for quick reference.

1 read

Small files are recommended to be read once, which makes the process simpler and faster.

func ReadAll(filePth string) ([]byte, error) {

 f, err := os.Open(filePth)

 if err != nil {

  return nil, err

 }
 return ioutil.ReadAll(f)

}

There's an easier way, and I use ioutil.ReadFile (filePth) a lot.

reads

Good balance between speed and memory footprint.

package main
import (

 "bufio"

 "io"

 "os"

)
func processBlock(line []byte) {

 os.Stdout.Write(line)

}
func ReadBlock(filePth string, bufSize int, hookfn func([]byte)) error {

 f, err := os.Open(filePth)

 if err != nil {

  return err

 }

 defer f.Close()
 buf := make([]byte, bufSize) //1 How many bytes are read at a time 

 bfRd := bufio.NewReader(f)

 for {

  n, err := bfRd.Read(buf)

  hookfn(buf[:n]) // n  Is the number of bytes successfully read 
  if err != nil { // Return immediately and ignore any errors encountered  EOF  The error message 

   if err == io.EOF {

    return nil

   }

   return err

  }

 }
 return nil

}
func main() {

 ReadBlock("test.txt", 10000, processBlock)

}

Read line by line

Line-by-line reading is sometimes really convenient, and performance can be slow, but it takes up very little memory.

package main
import (

 "bufio"

 "io"

 "os"

)
func processLine(line []byte) {

 os.Stdout.Write(line)

}
func ReadLine(filePth string, hookfn func([]byte)) error {

 f, err := os.Open(filePth)

 if err != nil {

  return err

 }

 defer f.Close()
 bfRd := bufio.NewReader(f)

 for {

  line, err := bfRd.ReadBytes('\n')

  hookfn(line) // In advance of error processing, even if an error occurs, the data that has been read is processed. 

  if err != nil { // Return immediately and ignore any errors encountered  EOF  The error message 

   if err == io.EOF {

    return nil

   }

   return err

  }

 }

 return nil

}
func main() {

 ReadLine("test.txt", processLine)

}

I hope this article has been helpful to your programming of GO language.