Golang 读取文件的几种方式

一、一次性读取全部文件

1、使用 os 包配合 ioutil 包读取

package main

import (
    "fmt"
    "io/ioutil"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        panic(err.Error())
    }
    defer file.Close()
    bytes, err := ioutil.ReadAll(file)
    if err != nil {
        panic(err.Error())
    }
    fmt.Println(string(bytes))
}

2、仅使用 ioutil 包读取

package main

import (
    "fmt"
    "io/ioutil"
)

func main() {
    bytes, err := ioutil.ReadFile("/yourPath/test.txt")
    if err != nil {
        panic(err.Error())
    }
    fmt.Println(string(bytes))
}

二、逐行读取文件

1、使用 bufio.NewReader 方法

package main

import (
    "bufio"
    "fmt"
    "io"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    i := 0
    for {
        line, _, err := reader.ReadLine()
        if err == io.EOF {
            break
        }
        i++
        fmt.Printf("line%d: %s \n", i, string(line))
    }
}

2、使用 bufio.NewScanner 方法

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    scanner := bufio.NewScanner(file)
    i := 0
    for scanner.Scan() {
        line := scanner.Text()
        i++
        fmt.Printf("line%d: %s \n", i, string(line))
    }
}

三、按字节读取文件

1、使用 file.Read 每次读取固定字节

package main

import (
    "fmt"
    "io"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    buf := make([]byte, 1024)
    bytes := make([]byte, 0)
    for {
        // 如果存在中文此方式可能出现乱码
        size, err := file.Read(buf)
        if err == io.EOF || size == 0 {
            break
        }
        bytes = append(bytes, buf[:size]...)
        // 加入分隔符验证
        // bytes = append(bytes, []byte("###")...)
    }
    fmt.Println(string(bytes))
}

2、使用 bufio.Read 每次读取固定字节

package main

import (
    "bufio"
    "fmt"
    "io"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    buf := make([]byte, 50)
    bytes := make([]byte, 0)
    for {
        // 如果存在中文此方式可能出现乱码
        size, err := reader.Read(buf)
        if err == io.EOF || size == 0 {
            break
        }
        bytes = append(bytes, buf[:size]...)
        // 加入分隔符验证
        // bytes = append(bytes, []byte("###")...)
    }
    fmt.Println(string(bytes))
}

3、使用 bufio.ReadByte 每次读取一个字节

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/Users/van/WorkSpace/go/learngo/fileOperation/file/ID2Path_size.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    bytes := make([]byte, 0)
    for {
        byte, err := reader.ReadByte()
        if err != nil {
            break
        }
        bytes = append(bytes, byte)
        // fmt.Printf("%s \n", string(byte))
    }
    fmt.Printf("content: %s \n", string(bytes))
}

4、使用 bufio.ReadRune 每次读取一个字符

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    runes := make([]rune, 0)
    for {
        readRune, size, err := reader.ReadRune()
        if err != nil || size == 0 {
            break
        }
        runes = append(runes, readRune)
        // fmt.Printf("%d - %s \n", size, string(readRune))
    }
    fmt.Printf("content: %s \n", string(runes))
}

四、按分隔符读取文件

1、 bufio.ReadBytes

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    bytes := make([]byte, 0)
    for {
        bytesTmp, err := reader.ReadBytes('\n')
        if err != nil {
            break
        }
        bytes = append(bytes, bytesTmp...)
        // fmt.Printf("%s \n", string(bytesTmp))
    }
    fmt.Printf("content: %s \n", string(bytes))
}

2、bufio.ReadSlice

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    bytes := make([]byte, 0)
    for {
        line, err := reader.ReadSlice('\n')
        if err != nil {
            break
        }
        bytes = append(bytes, line...)
        // fmt.Printf("%s \n", string(line))
    }
    fmt.Printf("content: %s \n", string(bytes))
}

3、bufio.ReadString

package main

import (
    "bufio"
    "fmt"
    "log"
    "os"
)

func main() {
    file, err := os.Open("/yourPath/test.txt")
    if err != nil {
        log.Fatalf("open file failed: %s \n", err.Error())
    }
    defer file.Close()
    reader := bufio.NewReader(file)
    var content string
    for {
        str, err := reader.ReadString('\n')
        if err != nil {
            break
        }
        content += str
        // fmt.Printf("%s \n", str)
    }
    fmt.Printf("content: %s \n", content)
}

以上，Van(完)。