生命不止，继续 go go go !!!
读写文件应该是在开发过程中经常遇到的，今天要跟大家一起分享的就是在golang的世界中，如何读写文件。
使用io/ioutil进行读写文件
先回忆下之前的ioutil包介绍：
Go语言学习之ioutil包(The way to go)
其中提到了两个方法：
func ReadFile
func ReadFile(filename string) ([]byte, error)
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ReadFile reads the file named by filename and returns the contents. A successful call returns err == nil, not err == EOF. Because ReadFile reads the whole file, it does not treat an EOF from Read as an error to be reported.
func WriteFile
func WriteFile(filename string, data []byte, perm os.FileMode) error
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WriteFile writes data to a file named by filename. If the file does not exist, WriteFile creates it with permissions perm; otherwise WriteFile truncates it before writing.
读文件：
package mainimport ( "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)}
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写文件：
package mainimport ( "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)}
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使用os进行读写文件
同样，先回忆下之前的os包的介绍：
Go语言学习之os包中文件相关的操作(The way to go)
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)
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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()
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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)
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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 mainimport ( "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) }}
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读方法
package mainimport ( "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()}
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写方法
package mainimport ( "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()}
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几种读取文件方法速度比较
package mainimport ( "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) } if 0 == 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) } if 0 == 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))}
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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
再分享一下我老师大神的人工智能教程吧。零基础！通俗易懂！风趣幽默！还带黄段子！希望你也加入到我们人工智能的队伍中来！https://blog.csdn.net/jiangjunshow