tailreader

tailreader

tailreader is a Go package that implements an io.Reader that tails a file.

It is intended to be used for binary files that are being written to by another process. It does not implement any kind of "line" reading and thus is fully compatible with the io.Reader interface and agnostic to the file's content.

Installation

go get -u github.com/maurice2k/tailreader

Usage

package main

import (
	"io"
	"log"
	"time"

	"github.com/maurice2k/tailreader"
)

func main() {
	tr, err := tailreader.NewTailingReader(
		"/tmp/test/the-file-to-tail",
		tailreader.WithWaitForFile(true, 30*time.Second), // wait for file to appear, but only for 30 seconds
		tailreader.WithIdleTimeout(60*time.Second),       // close reader if no data is read for 60 seconds
		tailreader.WithCloseOnDelete(true),               // close reader if file is deleted
	)
	if err != nil {
		log.Fatal(err)
	}
	defer tr.Close()

	// if you don't want to wait within tr.Read() you can call tr.WaitForFile()
	// upfront and then start reading, which will block until the file is available
	// or the timeout is reached

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

	buf := make([]byte, 1024)
	for {
		n, err := tr.Read(buf)

		if err == io.EOF {
			// there is no more data to read
			break
		} else if err != nil {
			log.Fatal(err)
		}

		log.Print(string(buf[:n]))
	}
}

License

tailreader is available under the MIT license.