[Go] 跨平台文件系统监控工具 fsnotify 应用举例

项目地址：https://github.com/fsnotify/fsnotify

fsnotify 能监控指定文件夹内 文件的修改情况，如 文件的 增加、删除、修改、重命名等操作。

官方给出了以下注意事项：

When a file is moved to another directory is it still being watched?

No (it shouldn't be, unless you are watching where it was moved to).

When I watch a directory, are all subdirectories watched as well?

No, you must add watches for any directory you want to watch (a recursive watcher is on the roadmap #18).

Do I have to watch the Error and Event channels in a separate goroutine?

As of now, yes. Looking into making this single-thread friendly (see howeyc #7)

Why am I receiving multiple events for the same file on OS X?

Spotlight indexing on OS X can result in multiple events (see howeyc #62). A temporary workaround is to add your folder(s) to the Spotlight Privacy settings until we have a native FSEvents implementation (see #11).

How many files can be watched at once?

There are OS-specific limits as to how many watches can be created:

• Linux: /proc/sys/fs/inotify/max_user_watches contains the limit, reaching this limit results in a "no space left on device" error.
• BSD / OSX: sysctl variables "kern.maxfiles" and "kern.maxfilesperproc", reaching these limits results in a "too many open files" error.

最为注意的一点是：

文件夹中的子文件夹，还需自己去添加监控，fsnotify 本身不提供递归循环监控功能！

应用举例

package main

import (
        "github.com/fsnotify/fsnotify"
        "log"
        "runtime"
)

func main() {
        // 监控路径列表
        paths := []string{
                "/Users/jianbao/GoglandProjects/fiisoo/src/test/ch0",
                "/Users/jianbao/GoglandProjects/fiisoo/src/test/ch1",
        }

        watcher, err := fsnotify.NewWatcher()
        if err != nil {
                log.Fatalf("Failed to create watcher: %s", err)
        }
        defer watcher.Close()

        exit := make(chan bool)

        go func() {
                for {
                        select {
                        case e := <-watcher.Events:
                                log.Println("修改文件：" + e.Name)
                                log.Println("修改类型：" + e.Op.String())
                        case err := <-watcher.Errors:
                                log.Printf("Watcher error: %s\n", err.Error()) // No need to exit here
                        }
                }
        }()

        log.Println("Initializing watcher...")
        for _, path := range paths {
                log.Printf("Watching: %s\n", path)
                err = watcher.Add(path)
                if err != nil {
                        log.Fatalf("Failed to watch directory: %s", err)
                }
        }

        <-exit // 用来 阻塞应用不退出，只能通过“杀死进程”的方式退出，如 按住 Ctrl + C 快捷键强制推出
        runtime.Goexit()
}