如何在 Go 中讀取文字檔？

Reading Text Files in Go

In Go, reading text files involves using the os and io packages. Here's a breakdown of how it works:

Opening the File

The first step is to open the text file using the os.Open() function. This function returns a *os.File pointer, which represents the file descriptor. Here's an example:

file, err := os.Open("file.txt")
if err != nil {
    log.Fatal(err)
}

Reading the File Contents

Once the file is opened, you can access its contents. There are several ways to do this:

1. Using io.ReadAll():

This function reads all the content of the file into a byte slice. It's efficient if you need to read the entire file at once.

b, err := io.ReadAll(file)
fmt.Print(b)

2. Using *os.File.Read():

You can also read the file in chunks. This is useful if you need to process the data gradually.

buf := make([]byte, 32*1024) // Custom buffer size

for {
    n, err := file.Read(buf)

    if n > 0 {
        fmt.Print(buf[:n])
    }

    if err == io.EOF {
        break
    }

    if err != nil {
        log.Fatal(err)
    }
}

3. Using bufio.Scanner:

The bufio package provides a convenient way to scan the file and read it line by line.

scanner := bufio.NewScanner(file)

for scanner.Scan() {
    fmt.Println(scanner.Text())
}

Closing the File

When you're done reading the file, don't forget to close it to release resources. The *os.File type implements the io.Closer interface, so you can use file.Close().

Further Resources

• Go File Cheatsheet: https://www.digitalocean.com/community/tutorials/golang-reading-and-writing-files#how-to-read-a-file

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