golang笔记：读写文件

读取文件

package main
import (
    "fmt"
    "io/ioutil"
    "strings"
    "os"
    "strconv"
    "bufio"
)

func main() {
   Ioutil("mytestfile.txt")
   OsIoutil("mytestfile.txt")
   FileRead("mytestfile.txt")
   BufioRead("mytestfile.txt")
    }


func Ioutil(name string) {
    if contents,err := ioutil.ReadFile(name);err == nil {
        //因为contents是[]byte类型，直接转换成string类型后会多一行空格,需要使用strings.Replace替换换行符
        result := strings.Replace(string(contents),"\n","",1)
        fmt.Println("Use ioutil.ReadFile to read a file:",result)
        }
    }

func OsIoutil(name string) {
      if fileObj,err := os.Open(name);err == nil {
      //if fileObj,err := os.OpenFile(name,os.O_RDONLY,0644); err == nil {
        defer fileObj.Close()
        if contents,err := ioutil.ReadAll(fileObj); err == nil {
            result := strings.Replace(string(contents),"\n","",1)
            fmt.Println("Use os.Open family functions and ioutil.ReadAll to read a file :",result)
            }

        }
}


func FileRead(name string) {
    if fileObj,err := os.Open(name);err == nil {
        defer fileObj.Close()
        //在定义空的byte列表时尽量大一些，否则这种方式读取内容可能造成文件读取不完整
        buf := make([]byte, 1024)
        if n,err := fileObj.Read(buf);err == nil {
               fmt.Println("The number of bytes read:"+strconv.Itoa(n),"Buf length:"+strconv.Itoa(len(buf)))
               result := strings.Replace(string(buf),"\n","",1)
               fmt.Println("Use os.Open and File's Read method to read a file:",result)
            }
    }
}

func BufioRead(name string) {
    if fileObj,err := os.Open(name);err == nil {
        defer fileObj.Close()
        //一个文件对象本身是实现了io.Reader的 使用bufio.NewReader去初始化一个Reader对象，存在buffer中的，读取一次就会被清空
        reader := bufio.NewReader(fileObj)
        //使用ReadString(delim byte)来读取delim以及之前的数据并返回相关的字符串.
        if result,err := reader.ReadString(byte('@'));err == nil {
            fmt.Println("使用ReadSlince相关方法读取内容:",result)
        }
        //注意:上述ReadString已经将buffer中的数据读取出来了，下面将不会输出内容
        //需要注意的是，因为是将文件内容读取到[]byte中，因此需要对大小进行一定的把控
        buf := make([]byte,1024)
        //读取Reader对象中的内容到[]byte类型的buf中
        if n,err := reader.Read(buf); err == nil {
            fmt.Println("The number of bytes read:"+strconv.Itoa(n))
            //这里的buf是一个[]byte，因此如果需要只输出内容，仍然需要将文件内容的换行符替换掉
            fmt.Println("Use bufio.NewReader and os.Open read file contents to a []byte:",string(buf))
        }


    }
}

写文件

package main
import (
    "os"
    "io"
    "fmt"
    "io/ioutil"
    "bufio"
)

func main() {
      name := "testwritefile.txt"
      content := "Hello, xxbandy.github.io!\n"
      WriteWithIoutil(name,content)
      contents := "Hello, xuxuebiao\n"
      //清空一次文件并写入两行contents
      WriteWithFileWrite(name,contents)
      WriteWithIo(name,content)
      //使用bufio包需要将数据先读到buffer中，然后在flash到磁盘中
      WriteWithBufio(name,contents)
}

//使用ioutil.WriteFile方式写入文件,是将[]byte内容写入文件,如果content字符串中没有换行符的话，默认就不会有换行符
func WriteWithIoutil(name,content string) {
    data :=  []byte(content)
    if ioutil.WriteFile(name,data,0644) == nil {
        fmt.Println("写入文件成功:",content)
        }
    }

//使用os.OpenFile()相关函数打开文件对象，并使用文件对象的相关方法进行文件写入操作
//清空一次文件
func WriteWithFileWrite(name,content string){
    fileObj,err := os.OpenFile(name,os.O_RDWR|os.O_CREATE|os.O_TRUNC,0644)
    if err != nil {
        fmt.Println("Failed to open the file",err.Error())
        os.Exit(2)
    }
    defer fileObj.Close()
    if _,err := fileObj.WriteString(content);err == nil {
        fmt.Println("Successful writing to the file with os.OpenFile and *File.WriteString method.",content)
    }
    contents := []byte(content)
    if _,err := fileObj.Write(contents);err == nil {
        fmt.Println("Successful writing to thr file with os.OpenFile and *File.Write method.",content)
    }
}


//使用io.WriteString()函数进行数据的写入
func WriteWithIo(name,content string) {
    fileObj,err := os.OpenFile(name,os.O_RDWR|os.O_CREATE|os.O_APPEND,0644)
    if err != nil {
        fmt.Println("Failed to open the file",err.Error())
        os.Exit(2)
    }
    if  _,err := io.WriteString(fileObj,content);err == nil {
        fmt.Println("Successful appending to the file with os.OpenFile and io.WriteString.",content)
    }
}

//使用bufio包中Writer对象的相关方法进行数据的写入
func WriteWithBufio(name,content string) {
    if fileObj,err := os.OpenFile(name,os.O_RDWR|os.O_CREATE|os.O_APPEND,0644);err == nil {
        defer fileObj.Close()
        writeObj := bufio.NewWriterSize(fileObj,4096)
        //
       if _,err := writeObj.WriteString(content);err == nil {
              fmt.Println("Successful appending buffer and flush to file with bufio's Writer obj WriteString method",content)
           }

        //使用Write方法,需要使用Writer对象的Flush方法将buffer中的数据刷到磁盘
        buf := []byte(content)
        if _,err := writeObj.Write(buf);err == nil {
            fmt.Println("Successful appending to the buffer with os.OpenFile and bufio's Writer obj Write method.",content)
            if  err := writeObj.Flush(); err != nil {panic(err)}
            fmt.Println("Successful flush the buffer data to file ",content)
        }
        }
}