SYNOPSIS

     use Logfile::Tail::Switch;
     use Time::HiRes 'sleep'; # for subsecond sleep
    
     my $tail = Logfile::Tail::Switch->new(
         glob => "/s/example.com/syslog/http_access.*.log",
     );
    
     # tail
     while (1) {
         my $line = $tail->getline;
         if (length $line) {
             print $line;
         } else {
            sleep 0.1;
         }
     }

DESCRIPTION

    This class can be used to tail a file, but switch when a file of a
    newer name appears. For example, on an Spanel server, the webserver is
    configured to write to daily log files:

     /s/<SITE-NAME>/syslog/http_access.<YYYY>-<MM>-<DD>.log
     /s/<SITE-NAME>/syslog/https_access.<YYYY>-<MM>-<DD>.log

    So, when tailing you will need to switch to a new log file if you cross
    day boundary.

    When using this class, you specify a glob pattern of files, e.g.
    /s/example.com/syslog/http_access.*.log. Then you call the getline
    method.

    This class will first select the newest file (via asciibetical sorting)
    from the glob pattern and tail it. Then, periodically (by default at
    most every 5 seconds) the glob pattern will be checked again. If there
    is one or more newer files, they will be read in full and then tail-ed,
    until an even newer file comes along. For example, this is the list of
    files in /s/example.com/syslog at time t1:

     http_access.2017-06-05.log.gz
     http_access.2017-06-06.log
     http_access.2017-06-07.log

    http_access.2017-06-07.log will first be tail-ed. When
    http_access.2017-06-08.log appears at time t2, this file will be read
    from start to finish then tail'ed. When http_access.2017-06-09.log
    appears the next day, that file will be read then tail'ed. And so on.

METHODS

 Logfile::Tail::Switch->new($glob [, \%opts ]) => obj

    Constructor.

    Known options:

      * check_freq => posint (default: 5)

 $tail->getline() => str

    Will return the next line or empty string if no new line is available.

SEE ALSO

    File::Tail, File::Tail::Dir, IO::Tail

    Tie::Handle::TailSwitch

    tailswitch from App::tailswitch

    Spanel, http://spanel.info.