How to use Go language for file operations?

With the development of the Internet, the generation and processing of large amounts of data have become routine matters in daily work. Under such circumstances, file operations are undoubtedly an essential skill for programmers.

As a simple and efficient programming language, Go language has excellent performance in file operations. With the powerful features of the Go language, you can easily perform operations such as reading, writing, and modifying files. Let's take a closer look at how to use the Go language for file operations.

1. Reading files

Go language provides two ways to read files, one is based on cache bufio.Scanner, and the other is based on streaming os.File. Let’s look at the cache-based approach first.

First, we need to open a file, you can use the os.Open() function, the code is as follows:

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

When opening a file, you need to pay attention to exception handling. If the file does not exist or there is an error opening the file, the program will throw a panic and output an error message. At this time, we can use the log.Fatal() function to print the error message and exit the program.

Next, we can use the bufio.NewScanner() function to read the file. The code is as follows:

scanner := bufio.NewScanner(file)
for scanner.Scan() {
    fmt.Println(scanner.Text())  // 输出每行文本内容
}
if err := scanner.Err(); err != nil {  // 判断是否读取到文件尾
    log.Fatal(err)
}

The scanner.Scan() function in the code can scan each line of text in the file and store it in scanner.Text(). After the loop completes, if the file has not reached the end of the file, an error will be thrown.

Another stream-based reading method is slightly different. The usage is as follows:

file, err := os.Open("filename.txt")
if err != nil {
    panic(err)
}
defer file.Close()

reader := bufio.NewReader(file)
for {
    line, err := reader.ReadString('
')
    if err == io.EOF {
        break
    } else if err != nil {
        panic(err)
    }
    fmt.Print(line)
}

After the file is read, we need to ensure that the file is closed, which can be achieved through the defer keyword. I won’t go into details here.

2. Writing of files

In the Go language, the writing operation of files is also very simple. We can use the os.Create() function and the io.WriteString() function to achieve this.

First, we need to open a file and prepare to write data:

file, err := os.Create("filename.txt")
if err != nil {
    panic(err)
}
defer file.Close()

Next, we can write data through the io.WriteString() function:

_, err = io.WriteString(file, "Hello World!
")
if err != nil {
    panic(err)
}

# The ##writeString function writes data to a file and returns the number of bytes written and possible errors. It should be noted that we need to manually add newline symbols after writing the data, otherwise the data will be crowded together.

File copying

In the actual development process, file copying is also a frequently used operation. The Go language provides the io.Copy() function to easily implement the file copy function.

The code is as follows:

src, err := os.Open("src.txt")
if err != nil {
    panic(err)
}
defer src.Close()

dst, err := os.Create("dst.txt")
if err != nil {
    panic(err)
}
defer dst.Close()

_, err = io.Copy(dst, src)
if err != nil {
    panic(err)
}

First open the source file and the target file, and ensure that they are closed after the operation is completed. We can then use io.Copy() to copy the source file contents to the target file. The value returned by the function tells us the number of bytes and possible errors.

Renaming and deleting files

Renaming and deleting files are also common operations. We can do this using the os.Rename() and os.Remove() functions.

The usage of renaming is as follows:

err := os.Rename("oldname.txt", "newname.txt")
if err != nil {
    panic(err)
}

The usage of deleting files is even simpler:

err := os.Remove("filename.txt")
if err != nil {
    panic(err)
}

It should be noted that once the operation of deleting files is performed, it cannot be undone. Please Use with caution.

Summary

In this article, we introduced the basic knowledge of file operations in Go language, including reading, writing, copying, renaming and deleting files. Mastering these skills can make it easier for developers to implement various file operation needs, and improve development efficiency and program robustness.

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