GO语言使用Fprint系列写入文件

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我是靠谱客的博主孤独云朵，最近开发中收集的这篇文章主要介绍GO语言使用Fprint系列写入文件，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

首先先了解Fp系列：

Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error)

Fprint(w io.Writer, a ...interface{}) (n int, err error)

Fprintln(w io.Writer, a ...interface{}) (n int, err error)

Fprintf() 根据 format格式说明符将内容格式化写入文件，返回内容是写入的字节与错误。

Fprint() 与Fprintln() 按照默认格式将内容写入文件。区别与print型与println型一致。

拿Fprintln举例，其他类似：

package main
import (
"fmt"
"log"
"os"
)
func main() {
testRetFile, err := os.OpenFile("./json.txt", os.O_WRONLY|os.O_CREATE, 0666)
if err != nil {
log.Println(err)
}
num, err :=	fmt.Fprintln(testRetFile, "do you love me, my dear")
if err != nil {
log.Println(err)
}
fmt.Println(num)
}

结果：24（返回字节数）

在同级目录生成json.txt文件并且内容为

do you love me, my dear

补充说明源码：

Fprintf：

// Fprintf formats according to a format specifier and writes to w.
// It returns the number of bytes written and any write error encountered.
func Fprintf(w io.Writer, format string, a ...interface{}) (n int, err error) {
p := newPrinter()
p.doPrintf(format, a)
n, err = w.Write(p.buf)
p.free()
return
}

Fprint:

// Fprint formats using the default formats for its operands and writes to w.
// Spaces are added between operands when neither is a string.
// It returns the number of bytes written and any write error encountered.
func Fprint(w io.Writer, a ...interface{}) (n int, err error) {
p := newPrinter()
p.doPrint(a)
n, err = w.Write(p.buf)
p.free()
return
}

Fprintln:

// Fprintln formats using the default formats for its operands and writes to w.
// Spaces are always added between operands and a newline is appended.
// It returns the number of bytes written and any write error encountered.
func Fprintln(w io.Writer, a ...interface{}) (n int, err error) {
p := newPrinter()
p.doPrintln(a)
n, err = w.Write(p.buf)
p.free()
return
}