NAME
Devel::EndStats - Display run time and dependencies after running code

VERSION
This document describes version 0.211 of Devel::EndStats (from Perl
distribution Devel-EndStats), released on 2023-05-12.

SYNOPSIS
# from the command line
% perl -MDevel::EndStats=time_hires,1 script.pl

##### sample output #####
<normal script output, if any...>

# BEGIN stats from Devel::EndStats
# Program runtime duration: 0.055s
# Total number of required files loaded: 132
# Total number of required lines loaded: 48772
# END stats

##### sample output (with verbose=1 & time_hires=1, some cut) #####
<normal script output, if any...>

# BEGIN stats from Devel::EndStats
# Program runtime duration: 0.055s
# Total number of required files loaded: 132
# Total number of required lines loaded: 48772
# # 1 1747 lines 0.023489s( 43%) Log/Any/App.pm (loaded by main)
# # 52 1106 lines 0.015112s( 28%) Log/Log4perl/Logger.pm (loaded by Log::Log4perl)
# # 17 190 lines 0.011983s( 22%) Log/Any/Adapter.pm (loaded by Log::Any::App)
# # 18 152 lines 0.011679s( 21%) Log/Any/Manager.pm (loaded by Log::Any::Adapter)
# # 5 981 lines 0.007299s( 13%) File/Path.pm (loaded by Log::Any::App)
...
# END stats

DESCRIPTION
Devel::EndStats runs in the END block, displaying various statistics
about your program, such as:

* how many seconds the program ran;

* how many required files and total number of lines loaded (from
%INC);

* etc.

It works by installing a hook in @INC to record the loading of modules.

Some notes/caveats:

Devel::EndStats should be loaded before other modules, for example by
running it on the command-line, as shown in the SYNOPSIS.

KNOWN ISSUES
* Timing and memory usage is inclusive instead of exclusive.

OPTIONS
Some options are accepted. They can be passed via the use statement:

# from the command line
% perl -MDevel::EndStats=verbose,1 script.pl

# from script
use Devel::EndStats verbose=>1;

or via the "PERL_DEVEL_ENDSTATS_OPTS" environment variable:

% PERL_DEVEL_ENDSTATS_OPTS='verbose=1' perl -MDevel::EndStats script.pl

If you use the later, you will need to use "use" and not "require" to
load "Devel::EndStats", because reading the environment variable is done
in the "import()" hook of the module.

* verbose

Bool, default 0. Can also be set via "VERBOSE" environment variable.
If set to true, display more statistics (like per-module
statistics).

* debug

Bool, default 0. Can also be set via "DEBUG" environment variable.
If set to true, display debugging messages to stderr.

* time_hires

Bool, default 0. By default, time is measured using the builtin
"time()" which only has 1-second precision. To enable subsecond
precision, set this option to true. Setting this option to true will
load Time::HiRes and affect the results.

* sort

String, default "caller". Set how to sort the list of loaded modules
('file' = by file, 'time' = by load time, 'caller' = by first
caller's package, 'order' = by order of loading, 'lines' = by number
of lines). Only relevant when 'verbose' is on.

* force

Bool, default 0. By default, if BEGIN phase did not succeed, stats
will not be shown. This option forces displaying the stats.

* hide_core

Bool, default 0. Whether to hide core modules while listing modules
in "verbose" mode. When this is set to true, will load
Module::CoreList, so that will affect the results.

* hide_noncore

Bool, default 0. Whether to hide non-core modules while listing
modules in "verbose" mode. When this is set to true, will load
Module::CoreList, so that will affect the results.q

* show_memsize

Bool, default 0. Whether to show memory usage information. Currently
this is done by probing "/proc/$$/statm" because some other memory
querying modules are unusable (e.g. Devel::SizeMe currently
segfaults on my system, "Devel::InterpreterSize" is too heavy).

FAQ
What is the purpose of this module?
This module might be useful during development. I first wrote this
module when trying to reduce startup overhead of a command line
application, by looking at how many modules the app has loaded and try
to avoid loading modules whenever it's unnecessary.

Why are some modules always shown as being already loaded despite me not having loaded any of such modules?
These are "Devel::EndStats" itself and modules that are loaded by
"Devel::EndStats", e.g. "Time::HiRes", "Module::CoreList", and modules
that are loaded by *those* modules.

Why are some modules have 'Seq' (sequence) value of '?'
These are modules that are loaded before "Devel::EndStats" and had not
been traced by "Devel::EndStats"'s @INC hook.

PERL_DEVEL_ENDSTATS_OPTS is not observed!
Make sure you load "Devel::EndStats" using "use" and not "require", or
make sure you "import()" the module, because reading of the environment
variable is done in the "import()" hook.

How to measure subsecond times?
Set option "time_hires" to true. Either from the "use" line:

# in perl code
use Devel::EndStats time_hires=>1;

# on the command line
% perl -MDevel::EndStats=time_hires,1

or from the environment variable "PERL_DEVEL_ENDSTATS_OPTS":

% PERL_DEVEL_ENDSTATS_OPTS="time_hires=1" perl -MDevel::EndStats ...

Can you add (so and so) information to the stats?
Sure, if it's useful. As they say, (comments|patches) are welcome.

ENVIRONMENT
VERBOSE
Bool. If set to true, will set "verbose" option to true.

DEBUG
Bool. If set to true, will set "debug" option to true.

PERL_DEVEL_ENDSTATS_OPTS
String. A space-separated key-value pairs to set options.

HOMEPAGE
Please visit the project's homepage at
<https://metacpan.org/release/Devel-EndStats>.

SOURCE
Source repository is at
<https://github.com/perlancar/perl-Devel-EndStats>.

SEE ALSO
There are many modules on CPAN that can be used to generate dependency
information for your code. Neil Bowers has written a review
<http://neilb.org/reviews/dependencies.html> that covers most of them.

AUTHOR
perlancar <perlancar@cpan.org>

CONTRIBUTORS
* Neil Bowers <neil@bowers.com>

* Steven Haryanto <stevenharyanto@gmail.com>

CONTRIBUTING
To contribute, you can send patches by email/via RT, or send pull
requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You
can simply modify the code, then test via:

% prove -l

If you want to build the distribution (e.g. to try to install it locally
on your system), you can install Dist::Zilla,
Dist::Zilla::PluginBundle::Author::PERLANCAR,
Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two
other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps
required beyond that are considered a bug and can be reported to me.

COPYRIGHT AND LICENSE
This software is copyright (c) 2023, 2015, 2014, 2013, 2012, 2010 by
perlancar <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.

BUGS
Please report any bugs or feature requests on the bugtracker website
<https://rt.cpan.org/Public/Dist/Display.html?Name=Devel-EndStats>

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.