go to read and write files

There are many ways to read and write files go, here we choose ioutil package

To read the file into memory

main Package 

Import ( 
    " IO / ioutil " 
    " FMT " 
) 

FUNC main () { 
    data, ERR: = ioutil.ReadFile ( " a.txt " ) where # is returned by a data byte slice
     IF ERR =! nil { 
        FMT .Println ( " File Reading error " , ERR) 
    } 
    fmt.Println ( String (Data)) 
}

Speak binary file bind

packr Will static files (e.g.,  .txt files) into  .go a file, then, .go the file will be directly embedded into a binary file. packer Very intelligent, during development, you can get static files from disk rather than binary. During development, when only a static file changes, do not have to recompile.

package main

import (
    "fmt"

    "github.com/gobuffalo/packr"
)

func main() {
    box := packr.NewBox("../a.txt")
    data := box.String("test.txt")
    fmt.Println("Contents of file:", data)
}

Read the file line by line

main Package 

Import ( 
    " BUFIO " 
    " In Flag " 
    " FMT " 
    " log " 
    " OS " 
) 

FUNC main () { 
    // fptr: = flag.String ( " fpath " , " test.txt " , " File Read from path to " ) 
    //flag.Parse () 

    f, ERR: = os.Open (" a.txt " ) // required because bufio is a * os.File type, so we read another way, then introduce later
     IF ERR! = nil { 
        log.Fatal(err) 
    }
    defer func() {
        if err = f.Close(); err != nil {
        log.Fatal(err)
    }
    }()
    s := bufio.NewScanner(f)
    for s.Scan() {
        fmt.Println(s.Text())
    }
    err = s.Err()
    if err != nil {
        log.Fatal(err)
    }
}

Block read file

When the file is very large, especially in the case of insufficient amount of RAM memory, the entire file is read into memory does not make sense. A better approach is to read the file block. This can be done using bufio package.

package main

import (
    "bufio"
    "flag"
    "fmt"
    "log"
    "os"
)

func main() {
    //fptr := flag.String("fpath", "test.txt", "file path to read from")
    //flag.Parse()

    f, err := os.Open("a.txt")
    if err != nil {
        log.Fatal(err)
    }
    defer func() {
        if err = f.Close(); err != nil {
            log.Fatal(err)
        }
    }()
    r := bufio.NewReader(f)
    b := make([]byte, 3)
    for {
        _, err := r.Read(b)
        if err != nil {
            fmt.Println("Error reading file:", err)
            break
        }
        fmt.Println(string(b))
    }
}