Fix typo.

Fixes elastic#1927

Fixes elastic#1928

docs/tutorials/getting-started-with-logstash.asciidoc

@@ -146,7 +146,7 @@ Inputs, Outputs, Codecs and Filters are at the heart of the Logstash configurati
 ==== Inputs
 Inputs are the mechanism for passing log data to Logstash. Some of the more useful, commonly-used ones are:
 
-* *file*: reads from a file on the filesystem, much like the UNIX command "tail -0a"
+* *file*: reads from a file on the filesystem, much like the UNIX command "tail -0F"
 * *syslog*: listens on the well-known port 514 for syslog messages and parses according to RFC3164 format
 * *redis*: reads from a redis server, using both redis channels and also redis lists. Redis is often used as a "broker" in a centralized Logstash installation, which queues Logstash events from remote Logstash "shippers".
 * *lumberjack*: processes events sent in the lumberjack protocol. Now called https://github.com/elasticsearch/logstash-forwarder[logstash-forwarder].