GitHub - davidmoten/rxjava-file: RxJava observables for files including NIO events

Status: released to Maven Central

Requires Java 7.

Observable utilities for files:

tail a file (either lines or byte[])
trigger tail updates using Java 7 and later NIO WatchService events
or trigger tail updates using any Observable
stream WatchEvents from a WatchService
backpressure support
tested on Linux and Windows 7 (not OSX, help appreciated!)

Release Notes

Maven site reports are here including javadoc.

For RxJava 2.x see rxjava2-file.

Getting started

Add this maven dependency to your pom.xml:

<dependency>
  <groupId>com.github.davidmoten</groupId>
  <artifactId>rxjava-file</artifactId>
  <version>0.4.4</version>
</dependency>

How to build

git clone https://github.com/davidmoten/rxjava-file
cd rxjava-file
mvn clean install

Examples

Tail a text file with NIO

Tail the lines of the text log file /var/log/server.log as an Observable<String>:

import com.github.davidmoten.rx.FileObservable;
import rx.Observable;
import java.io.File; 
 
Observable<String> items = 
     FileObservable.tailer()
                   .file("/var/log/server.log")
                   .startPosition(0)
                   .sampleTimeMs(500)
                   .chunkSize(8192)
                   .utf8()
                   .tailText();

or, using defaults (will use default charset):

Observable<String> items = 
     FileObservable.tailer()
                   .file("/var/log/server.log")
                   .tailText();

Note that if you want the Observable<String> to be emitting line by line then wrap it with a call like StringObservable.split(observable, "\n"). StringObservable is in the RxJava rxjava-string artifact.

Tail a text file without NIO

The above example uses a WatchService to generate WatchEvents to prompt rereads of the end of the file to perform the tail.

To use polling instead (say every 5 seconds):

Observable<String> items = 
     FileObservable.tailer()
                   .file(new File("var/log/server.log"))
                   .source(Observable.interval(5, TimeUnit.SECONDS)
                   .tailText();

Tail a binary file with NIO

Observable<byte[]> items = 
     FileObservable.tailer()
                   .file("/tmp/dump.bin")
                   .tail();

Tail a binary file without NIO

Observable<byte[]> items = 
     FileObservable.tailer()
                   .file("/tmp/dump.bin")
                   .source(Observable.interval(5, TimeUnit.SECONDS)
                   .tail();