How to replace CRLF in golang

CRLF refers to Carriage Return and Line Feed, which is the standard for line breaks under Windows. Under Unix or Linux systems, LF (Line Feed) is used as the line break standard. When sharing files between different operating systems, some line break issues may arise. In Golang, we can use some simple methods to solve this problem.

1. Use bufio to convert CRLF and LF

The bufio package provides many useful functions and methods to handle file reading and writing operations. For the conversion of CRLF and LF, we can use two structures, Scanner and Writer.

package main

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

func main() {
    // 打开文件
    f, err := os.Open("test.txt")
    if err != nil {
        panic(err)
    }
    // 关闭文件
    defer f.Close()
    
    // 创建Scanner对象
    scanner := bufio.NewScanner(f)
    
    // 设置Scanner可以扫描CRLF换行符
    scanner.Split(bufio.ScanLines)
    
    for scanner.Scan() {
        // 将CRLF转换为LF
        line := scanner.Text()
        line = strings.Replace(line, "\r\n", "\n", -1)
        fmt.Println(line)
    }
}

In the above code, we first create a Scanner object and set it to scan CRLF newlines. Next, we use the Scan method to read each line and the Replace method to replace CRLF with LF.

If you want to replace LF with CRLF, you only need to modify the above Replace method to:

line = strings.Replace(line, "\n", "\r\n", -1)

Similarly, the conversion between CRLF and LF can also be achieved using bufio's Writer structure.

package main

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

func main() {
    // 打开文件
    f, err := os.Create("test.txt")
    if err != nil {
        panic(err)
    }
    // 关闭文件
    defer f.Close()
    
    // 创建Writer对象
    writer := bufio.NewWriter(f)
    
    // 写入文本内容，使用LF作为换行符
    text := "Hello, world!\nWelcome to Golang!\n"
    _, err = writer.WriteString(text)
    if err != nil {
        panic(err)
    }
    // 刷新缓冲区，同时将LF转换为CRLF
    err = writer.Flush()
    if err != nil {
        panic(err)
    }
}

In the above code, we create a Writer object and use LF as the newline character to write the text content. Next, use the Flush method to write the data in the buffer to the file, while converting LF to CRLF.

2. Use io.Copy to convert CRLF and LF

Another simple method is to use the io.Copy function. This function is used to copy the data in the source Reader to the target Writer, and can be used for file copying or file format conversion.

package main

import (
    "bytes"
    "io"
    "os"
)

func main() {
    // 打开源文件
    src, err := os.Open("test_win.txt")
    if err != nil {
        panic(err)
    }
    defer src.Close()
    
    // 打开目标文件
    dst, err := os.Create("test_unix.txt")
    if err != nil {
        panic(err)
    }
    defer dst.Close()
    
    // 将CRLF转换为LF
    io.Copy(dst, bytes.NewBufferString(strings.ReplaceAll(bufio.NewScanner(src).Text(), "\r\n", "\n")))
}

In the above code, we first open the source file and the target file. Then, use bufio's Scanner object to read each line of the source file and use the ReplaceAll method to replace CRLF with LF. Finally, use io.Copy to write the processed data to the target file.

3. Use strings.ReplaceAll to convert CRLF and LF

The last simple method is to use the ReplaceAll function in the strings package. This function can be used for replacement operations in strings.

package main

import (
    "fmt"
    "io/ioutil"
    "os"
    "strings"
)

func main() {
    // 读取源文件
    data, err := ioutil.ReadFile("test_win.txt")
    if err != nil {
        panic(err)
    }
    
    // 将CRLF转换为LF
    newData := strings.ReplaceAll(string(data), "\r\n", "\n")
    
    // 写入目标文件
    err = ioutil.WriteFile("test_unix.txt", []byte(newData), os.ModePerm)
    if err != nil {
        panic(err)
    }
    
    fmt.Println("Done!")
}

In the above code, we use the ReadFile function in the ioutil package to read the content of the source file, and use the ReplaceAll method to replace CRLF with LF. Finally, use the WriteFile function to write the processed data to the target file.

Summary:

Using the bufio and io packages in Golang can easily convert CRLF and LF. In addition, replacement operations in strings can also be easily implemented using the ReplaceAll function in the strings package. No matter which method is used, pay attention to the file encoding problem to avoid garbled characters.

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