go读写文本文件

一、文件读取

1. 将整个文件读取到内存中

package main

import (
        "flag"
        "fmt"
        "io/ioutil"
)

func main() {
        //从命令行标记参数中获取文件路径
        fptr := flag.String("fpath", "test.txt", "the file path to read from")
        flag.Parse()
        data, err := ioutil.ReadFile(*fptr)
        if err != nil {
                fmt.Println("File reading error: ", err)
        }
        fmt.Println(string(data))
}

2. 分块读取文件

package main

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

func main() {
        fptr := flag.String("fpath", "test.txt", "the file path to read from")
        flag.Parse()

        f, err := os.Open(*fptr)
        if err != nil {
                log.Fatal(err)
        }
        defer func() {
                if err := f.Close(); err != nil {
                        log.Fatal(err)
                }
        }()
        r := bufio.NewReader(f)
        b := make([]byte, 10)
        for {
                _, err := r.Read(b)
                if err != nil {
                        if err == io.EOF {
                                break
                        }
                        log.Fatal(err)
                }
                fmt.Println(string(b))
        }
}

3. 逐行读取文件

package main

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

func main() {
        fptr := flag.String("fpath", "test.txt", "the file path to read from")
        flag.Parse()

        f, err := os.Open(*fptr)
        if err != nil {
                log.Fatal(err)
        }
        defer func() {
                if err = f.Close(); err != nil {
                        log.Fatal(err)
                }
        }()
        s := bufio.NewScanner(f)
        for s.Scan() {
                fmt.Println(s.Text())
        }
        err = s.Err()
        if err != nil {
                log.Fatal(err)
        }
}

二、文件写入

1. 将字符串写入文件

package main

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

func main() {
        f, err := os.Create("test2.txt")
        if err != nil {
                log.Fatal(err)
        }
        defer func() {
                if err = f.Close(); err != nil {
                        log.Fatal(err)
                }
        }()
        l, err := f.WriteString("Hello world")
        if err != nil {
                log.Fatal(err)
        }
        fmt.Println(l, " bytes written successfully!")
}

2. 将字节写入文件

package main

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

func main() {
        f, err := os.Create("test2.txt")
        if err != nil {
                log.Fatal(err)
        }
        defer func() {
                if err = f.Close(); err != nil {
                        log.Fatal(err)
                }
        }()
        d := []byte{104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100}
        l, err := f.Write(d)
        if err != nil {
                log.Fatal(err)
        }
        fmt.Println(l, " bytes written successfully!")
}

3. 追加到文件

package main

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

func main() {
        f, err := os.OpenFile("test3.txt", os.O_APPEND|os.O_WRONLY, 0644)
        if err != nil {
                log.Fatal(err)
        }
        defer func() {
                if err = f.Close(); err != nil {
                        log.Fatal(err)
                }
        }()
        _, err = fmt.Fprintln(f, "Hello, my name is jet.")
        if err != nil {
                log.Fatal(err)
        }
}