读文件：

package main

import (

"fmt"

"io/ioutil"

)

func main() {

b, err := ioutil.ReadFile("test.log")

if err != nil {

fmt.Print(err)

}

fmt.Println(b)

str := string(b)

fmt.Println(str)

}

写文件：

package main

import (

"io/ioutil"

)

func check(e error) {

if e != nil {

panic(e)

}

}

func main() {

d1 := []byte("hello\ngo\n")

err := ioutil.WriteFile("test.txt", d1,0644)

check(err)

}

使用os进行读写文件

首先要注意的就是两个打开文件的方法：

func Open

func Open(name string) (*File, error)

Open opens the named file for reading. If successful, methods on the returned file can be used for reading; the associated file descriptor has mode O_RDONLY. If there is an error, it will be of type *PathError.

读文件：

fi, err := os.Open(path)

if err != nil {

panic(err)

}

defer fi.Close()

func OpenFile

需要提供文件路径、打开模式、文件权限

func OpenFile(name string, flag int, perm FileMode) (*File, error)

OpenFile is the generalized open call; most users will use Open or Create instead. It opens the named file with specified flag (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful, methods on the returned File can be used for I/O. If there is an error, it will be of type *PathError.

读文件：

package main

import (

"log"

"os"

)

func main() {

f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE,0755)

if err != nil {

log.Fatal(err)

}

if err := f.Close(); err != nil {

log.Fatal(err)

}

}

读方法

package main

import (

"bufio"

"fmt"

"io"

"io/ioutil"

"os"

)

func check(e error) {

if e != nil {

panic(e)

}

}

func main() {

f, err := os.Open("/tmp/dat")

check(err)

b1 := make([]byte,5)

n1, err := f.Read(b1)

check(err)

fmt.Printf("%d bytes: %s\n", n1, string(b1))

o2, err := f.Seek(6,0)

check(err)

b2 := make([]byte,2)

n2, err := f.Read(b2)

check(err)

fmt.Printf("%d bytes @ %d: %s\n", n2, o2, string(b2))

o3, err := f.Seek(6,0)

check(err)

b3 := make([]byte,2)

n3, err := io.ReadAtLeast(f, b3,2)

check(err)

fmt.Printf("%d bytes @ %d: %s\n", n3, o3, string(b3))

_, err = f.Seek(0,0)

check(err)

r4 := bufio.NewReader(f)

b4, err := r4.Peek(5)

check(err)

fmt.Printf("5 bytes: %s\n", string(b4))

f.Close()

}

写方法

package main

import (

"bufio"

"fmt"

"io/ioutil"

"os"

)

func check(e error) {

if e != nil {

panic(e)

}

}

func main() {

f, err := os.Create("/tmp/dat2")

check(err)

defer f.Close()

d2 := []byte{115,111,109,101,10}

n2, err := f.Write(d2)

check(err)

fmt.Printf("wrote %d bytes\n", n2)

n3, err := f.WriteString("writes\n")

fmt.Printf("wrote %d bytes\n", n3)

f.Sync()

w := bufio.NewWriter(f)

n4, err := w.WriteString("buffered\n")

fmt.Printf("wrote %d bytes\n", n4)

w.Flush()

}

几种读取文件方法速度比较

package main

import (

"bufio"

"fmt"

"io"

"io/ioutil"

"os"

"time"

)

func read0(path string) string {

f, err := ioutil.ReadFile(path)

if err != nil {

fmt.Printf("%s\n", err)

panic(err)

}

return string(f)

}

func read1(path string) string {

fi, err := os.Open(path)

if err != nil {

panic(err)

}

defer fi.Close()

chunks := make([]byte,1024,1024)

buf := make([]byte,1024)

for {

n, err := fi.Read(buf)

if err != nil && err != io.EOF {

panic(err)

}

if0 == n {

break

}

chunks = append(chunks, buf[:n]...)

}

return string(chunks)

}

func read2(path string) string {

fi, err := os.Open(path)

if err != nil {

panic(err)

}

defer fi.Close()

r := bufio.NewReader(fi)

chunks := make([]byte,1024,1024)

buf := make([]byte,1024)

for {

n, err := r.Read(buf)

if err != nil && err != io.EOF {

panic(err)

}

if0 == n {

break

}

chunks = append(chunks, buf[:n]...)

}

return string(chunks)

}

func read3(path string) string {

fi, err := os.Open(path)

if err != nil {

panic(err)

}

defer fi.Close()

fd, err := ioutil.ReadAll(fi)

return string(fd)

}

func main() {

file := "test.log"

start := time.Now()

read0(file)

t0 := time.Now()

fmt.Printf("Cost time %v\n", t0.Sub(start))

read1(file)

t1 := time.Now()

fmt.Printf("Cost time %v\n", t1.Sub(t0))

read2(file)

t2 := time.Now()

fmt.Printf("Cost time %v\n", t2.Sub(t1))

read3(file)

t3 := time.Now()

fmt.Printf("Cost time %v\n", t3.Sub(t2))

}

运行结果：

Cost time 4.0105ms

Cost time 11.5043ms

Cost time 7.0042ms

Cost time 2.4983ms

Cost time 4.4925ms

Cost time 11.0053ms

Cost time 5.0082ms

Cost time 2.9992ms

Cost time 3.9866ms

Cost time 15.0085ms

Cost time 7.5054ms

Cost time 2.5035ms

Cost time 4.9989ms

Cost time 14.0112ms

Cost time 7.5045ms

Cost time 3.508ms

Cost time 3.0043ms

Cost time 15.0265ms

Cost time 8.9884ms

Cost time 2.0036ms