/ 
Logfile-Tail-Switch-0.004
River stage one • 4 direct dependents • 5 total dependents
/ Logfile::Tail::Switch

NAME

Logfile::Tail::Switch - Tail a file, but switch when another file with newer name appears

VERSION

This document describes version 0.004 of Logfile::Tail::Switch (from Perl distribution Logfile-Tail-Switch), released on 2019-01-30.

SYNOPSIS

use Logfile::Tail::Switch;
use Time::HiRes 'sleep'; # for subsecond sleep

my $tail = Logfile::Tail::Switch->new(
    globs => ["/s/example.com/syslog/http_access.*.log"],
    # check_freq => 2,
    # tail_new => 0,
);

# 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 2 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.

PACKAGE VARIABLES

$WARN_NO_MATCH

Boolean, default 1. Whether to warn when the glob does not match any files.

METHODS

Logfile::Tail::Switch->new(%args) => obj

Constructor.

Known arguments:

  • globs => array

    Glob patterns.

  • check_freq => posint (default: 2)

  • tail_new => bool

    If set to true, then new file that appears will be tail'ed instead of read from the beginning.

$tail->getline() => str

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

HOMEPAGE

Please visit the project's homepage at https://metacpan.org/release/Logfile-Tail-Switch.

SOURCE

Source repository is at https://github.com/perlancar/perl-Logfile-Tail-Switch.

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Logfile-Tail-Switch

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

SEE ALSO

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

Tie::Handle::TailSwitch

tailswitch from App::tailswitch

Spanel, http://spanel.info.

AUTHOR

perlancar <perlancar@cpan.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2019, 2017 by perlancar@cpan.org.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.