How Can I Detect File Changes in Go?

Detecting File Changes in Go

Question:

How can I detect when a file changes using the Go programming language? Is there a way to emulate Linux's fcntl() functionality, which can notify when a specific file undergoes changes?

Answer:

While the fcntl() function is not available in Go, there are other techniques you can use to achieve file change detection.

Cross-Platform Method:

This method involves polling the file for changes at regular intervals:

func watchFile(filePath string) error {
    initialStat, err := os.Stat(filePath)
    if err != nil {
        return err
    }

    for {
        stat, err := os.Stat(filePath)
        if err != nil {
            return err
        }

        if stat.Size() != initialStat.Size() || stat.ModTime() != initialStat.ModTime() {
            break
        }

        time.Sleep(1 * time.Second)
    }

    return nil
}

This function repeatedly checks the file's size and modified time, and returns when a change is detected.

Usage Example:

doneChan := make(chan bool)

go func(doneChan chan bool) {
    defer func() {
        doneChan <- true
    }()

    err := watchFile("/path/to/file")
    if err != nil {
        fmt.Println(err)
    }

    fmt.Println("File has been changed")
}(doneChan)

<-doneChan

This example demonstrates how to use the watchFile function to detect file changes and notify the main routine via a channel.

Note:

This cross-platform method is not as efficient as a native system call but provides a simple and portable way to track file changes. It may be sufficient for certain use cases.

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