recwatch

recwatch

Watch filesystem changes recursively.

recwatch started out as a fork of looper (by Nathan Youngman), but most of the code is now original.

Features and limitations

• Can be used for watching filesystem changes recursively.
• Can be used for setting up a SSE (server-sent events) server, for serving filesystem changes as events.
• Filenames beginning with . or _ are ignored.
• The file search is concurrent.
• Will follow symlinks.
• Note that some systems may have a very low ulimit which may limit how many files can be watched at the same time.

Example usage

Short example

recwatch.EventServer(pathToWatch, "*", eventAddr, eventPath, refreshDuration)

Longer example

package main

import (
    "log"
    "os"
    "os/signal"
    "path/filepath"
    "strings"
    "time"

    "github.com/xyproto/recwatch"
)

func plural(passed time.Duration) string {
    if passed.Seconds() != 1 {
        return "s"
    }
    return ""
}

// Some errors are ignored since this is just a quick example
func main() {
    eventAddr := "0.0.0.0:5555"
    eventPath := "/"
    pathToWatch := "tempdir"
    refreshDuration, err := time.ParseDuration("350ms")
    if err != nil {
        log.Fatalln(err)
    }
    now := time.Now().UTC()
    _ = os.Mkdir(pathToWatch, 0755)
    recwatch.EventServer(pathToWatch, "*", eventAddr, eventPath, refreshDuration)
    URL := "http://" + strings.Replace(eventAddr, "0.0.0.0", "localhost", 1) + eventPath
    log.Printf("Serving filesystem events for %s as SSE (server-sent events) on %s\n", pathToWatch, URL)
    tempFileName := filepath.Join(pathToWatch, "hello.txt")
    _ = os.Remove(tempFileName)
    // Set up a handler for SIGINT (ctrl-c)
    quit := false
    c := make(chan os.Signal, 1)
    signal.Notify(c, os.Interrupt)
    go func() {
        for range c {
            // ctrl-c was pressed
            quit = true
            log.Println("ctrl-c was pressed, cleaning up")
            _ = os.Remove(tempFileName)
            _ = os.Remove(pathToWatch) // will only remove the directory if it's empty
            log.Println("done")
        }
    }()
    for {
        passed := time.Since(now)
        log.Printf("%.0f second%s passed. Visit %s to see events appear.\n", passed.Seconds(), plural(passed), URL)
        time.Sleep(1 * time.Second)
        if quit {
            break
        }
        log.Println("Creating and writing to " + tempFileName)
        data := []byte("Hi\n")
        err := os.WriteFile(tempFileName, data, 0644)
        if err != nil {
            log.Fatal(err)
        }
        time.Sleep(1 * time.Second)
        if quit {
            break
        }
        log.Println("Removing " + tempFileName)
        err = os.Remove(tempFileName)
        if err != nil {
            log.Fatal(err)
        }
        time.Sleep(1 * time.Second)
        if quit {
            break
        }
        if passed.Seconds() > 200 {
            log.Println("Time waits for no man.")
        }
    }
}

General info

• Version: 1.2.1
• License: BSD-2
• Author: Alexander F. Rødseth <xyproto@archlinux.org>