Go实现替换(覆盖)文件某一行内容的示例代码

$ cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

auto ens33
iface ens33 inet static
address 40.40.40.210
gateway 40.40.40.1
netmask 255.255.255.0

package main

import (
?? ?"bufio"
?? ?"fmt"
?? ?"io"
?? ?"os"
?? ?"strings"
)

func main() {
? ? //读写方式打开文件
?? ?file, err := os.OpenFile("/etc/network/interfaces", os.O_RDWR, 0666)
?? ?if err != nil {
?? ??? ?fmt.Println("open file filed.", err)
?? ??? ?return
?? ?}
? ? //defer关闭文件
?? ?defer file.Close()

? ? //获取文件大小
?? ?stat, err := file.Stat()
?? ?if err != nil {
?? ??? ?panic(err)
?? ?}
?? ?var size = stat.Size()
?? ?fmt.Println("file size:", size)

? ? //读取文件内容到io中
?? ?reader := bufio.NewReader(file)
?? ?pos := int64(0)
?? ?ip := "40.40.40.220"
?? ?gateway := "40.40.40.1"
?? ?netmask := "255.255.255.0"
?? ?for {
? ? ? ? //读取每一行内容
?? ??? ?line, err := reader.ReadString('\n')
?? ??? ?if err != nil {
? ? ? ? ? ? //读到末尾
?? ??? ??? ?if err == io.EOF {
?? ??? ??? ??? ?fmt.Println("File read ok!")
?? ??? ??? ??? ?break
?? ??? ??? ?} else {
?? ??? ??? ??? ?fmt.Println("Read file error!", err)
?? ??? ??? ??? ?return
?? ??? ??? ?}
?? ??? ?}
?? ??? ?fmt.Println(line)

? ? ? ? //根据关键词覆盖当前行
?? ??? ?if strings.Contains(line, "address") {
?? ??? ??? ?bytes := []byte("address " + ip + "\n")
?? ??? ??? ?file.WriteAt(bytes, pos)
?? ??? ?} else if strings.Contains(line, "gateway") {
?? ??? ??? ?bytes := []byte("gateway " + gateway + "\n")
?? ??? ??? ?file.WriteAt(bytes, pos)
?? ??? ?} else if strings.Contains(line, "netmask") {
?? ??? ??? ?bytes := []byte("netmask " + netmask + "\n")
?? ??? ??? ?file.WriteAt(bytes, pos)
?? ??? ?}

? ? ? ? //每一行读取完后记录位置
?? ??? ?pos += int64(len(line))
?? ?}
}