package Perinci::CmdLine::Manual::FAQ; # just to make podweaver happy

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# VERSION

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# ABSTRACT: FAQs

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=pod

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=head1 NAME

Perinci::CmdLine::Manual::FAQ - FAQs

=head1 VERSION

This document describes version 1.48 of Perinci::CmdLine::Manual::FAQ (from Perl distribution Perinci-CmdLine), released on 2015-10-22.

=head1 NOMENCLATURE

C<[PC::Classic]> denotes that the answer applies to L<Perinci::CmdLine::Classic>
only and not L<Perinci::CmdLine::Lite>. C<[PC::Lite]> denotes that the answer is
specific to Perinci::CmdLine::Lite. C<[PC::Any]> denotes that the answer is
specific to L<Perinci::CmdLine::Any>.

=head1 GENERAL

=head2 Why are there multiple frameworks/flavors for Perinci::CmdLine?

There are currently 3 (three) flavors of the framework:
L<Perinci::CmdLine::Classic>, L<Perinci::CmdLine::Lite>, and
L<Perinci::CmdLine::Inline>. Which one you should use depends on your needs,
because sadly, there is no one-size-fits-all.

B<Perinci::CmdLine::Classic.> Perinci::CmdLine::Classic (hereby called
PC:Classic) is the first flavor which I developed (and it used to be called just
Perinci::CmdLine). It has the most complete features as well as the prettiest
output, but as it grows in features, other things like startup overhead and
dependencies also grow.

B<Perinci::CmdLine::Lite.> So another project is started,
L<Perinci::CmdLine::Lite> (hereby called PC::Lite) that focuses on keeping
startup overhead low to avoid making tab completion delay noticeable. PC:Lite
aims to make CLI scripts typically start below 0.05s, while PC:Classic-based
scripts currently start in about 0.2-0.5s which causes a noticeable delay when
doing tab completion. PC:Lite also tries to reduce the number of dependencies
(from 100+ down to 30+ or so). Some PC:Classic features are still missing in
PC:Lite (see next question).

PC:Lite stays more lightweight by avoiding the use of libraries that have large
dependencies or add too much to startup overhead. This includes replacing
L<Perinci::Access> with L<Perinci::Access::Lite> for metadata access, avoiding
L<Text::ANSITable> for formatting results, and replacing L<Log::Any::App> (which
uses the relatively heavy L<Log::Log4perl>) with L<Log::Any::Adapter::Screen>
for logging.

Implementation-wise, the two share a lot of common code in the form of their
base class, L<Perinci::CmdLine::Base>. The interface is also 99% the same.

It is possible that in the future the two versions will merge.

B<Perinci::CmdLine::Inline.> There is another flavor called PC:Inline. The goal
of this flavor is to make your CLI scripts depend on nothing but Perl and the
core modules. (It is also possible to make PC:Classic- or PC:Lite-based CLI
script to also be freestanding by techniques like fatpacking or datapacking, but
the resulting packed script will be much larger.) It has the lowest number of
dependencies and the fastest startup overhead (around 0.01s). But currently it
also has the least features.

It reduces startup overhead further by skipping the Riap layer and prefetching
the Rinci metadata, precomputing the command-line options, and embedding all
these in the scripts.

See L<Perinci::CmdLine::Inline> for more details of the features it currently
supports. This flavor is suitable for simple CLI scripts that need to be as lean
and fast as possible, for example: L<hr> (in L<App::hr>) or L<gen-uuids> (in
L<App::UuidUtils>).

All the flavors share the basic concept: running your L<Rinci>-described
functions on the command-line.

So which one should you choose? PC:Lite is the sane default choice, unless you
need features that are currently not supported by PC:Lite, in which case you can
consider using PC:Classic. If you really need fast startup, you can opt for
PC:Inline. But note that when the backend function's Rinci metadata changes, you
will need to rebuild the script because the metadata is embedded in the script
(while in PC:Lite and PC:Classic, the script simply request the Rinci metadata
during runtime).

=head2 What Classic features are currently still missing in Lite?

=over

=item * More sophisticated formatting

Instead of L<Perinci::Result::Format> (especially for 'text*' formats which use
L<Data::Format::Pretty::Console> and L<Text::ANSITable>), to keep dependencies
minimal and formatting quick, PC::Lite uses the following simple rules that work
for a significant portion of common data structures:

1) if result is undef, print nothing.

2) if result is scalar, print it (with newline automatically added).

3) if result is an array of scalars (check at most 5 first rows), print it one
line for each element.

4) if result is a hash of scalars (check at most 5 keys), print a two column
table, first column is key and second column is value. Keys will be sorted.

5) if result is an array of hashes of scalars (check at most 5 elements), print
as table.

6) if result is an array of arrays of scalars (check at most 5 elements), print
as table.

7) otherwise print as JSON (after cleaning it with L<Data::Clean::JSON>).

YAML and the other formats are not supported.

Table is printed using the more lightweight and much faster
L<Text::Table::Tiny>.

PC::Classic supports more sophisticated formatting, can keep colored and
full-width Unicode characters stay aligned in a table.

=item * Support for extra protocols

Instead of L<Perinci::Access>, PC::Lite uses the more lightweight alternative
L<Perinci::Access::Lite> which does not support some URL schemes (riap+tcp,
riap+unix, riap+pipe). http/https and local are supported though.

=item * Extra stuffs that Perinci::Sub::Wrapper adds

PC::Classic uses function wrapper to automatically adds argument validation,
dependency checking, and so on. However, this adds too much overhead so PC:Lite
avoids it and do some of the stuffs by itself to avoid the overhead.

PC:Lite does argument validation, as well as dependency checking. But there are
other stuffs that Perinci::Sub::Wrapper adds that are not available, including:
result validation, validation of input stream (streaming argument) as well as
output stream (streaming result).

=item * Color themes

=item * Undo

=item * More advanced logging

Only logging to screen is currently supported by PC::Lite, using
L<Log::Any::Adapter::Screen>. PC::Classic, using L<Log::Any::App> can log to
files, directories, syslog, and other outputs.

=item * I18N

=item * The following environment variables

 PERINCI_CMDLINE_COLOR_THEME
 PERINCI_CMDLINE_SERVER
 COLOR
 UTF8

=back

=head2 What is Perinci::CmdLine::Any then?

This is a module that allows you to select PC::Classic or PC::Lite. So your
scripts do not need to be modified when user wants to switch between the two.

=head2 How does Perinci::CmdLine compare with other CLI-app frameworks?

The main difference is that Perinci::CmdLine accesses your code through L<Riap>
protocol, not directly. This means that aside from local Perl code,
Perinci::CmdLine can also provide CLI for code in remote hosts/languages. For a
very rough demo, download and run this PHP Riap::TCP server
https://github.com/sharyanto/php-Phinci/blob/master/demo/phi-tcpserve-terbilang.php
on your system. After that, try running:

 % peri-run riap+tcp://localhost:9090/terbilang --help
 % peri-run riap+tcp://localhost:9090/terbilang 1234

Everything from help message, calling, argument checking, tab completion works
for remote code as well as local Perl code.

=head2 But my application is OO? But I want an OO framework?

This framework is currently function-centric. There are already several OO-based
command-line frameworks on CPAN.

=head1 DEBUGGING

=head2 How do I enable/view log messages?

The framework produces log messages using L<Log::Any>. You can display them on
the screen, e.g. using L<Log::Any::Adapter::Screen> like:

 % perl -MLog::Any::Adapter=Screen,min_level,trace /path/to/yourscript.pl

or:

 % TRACE=1 PERL5OPT=-MLog::Any::Adapter::Screen yourscript.pl

Log::Any::Adapter::Screen has a few other options and observes a few other
environment variables (e.g. for prefixing with timestamp, etc). See its
documentation for more details.

For sending logs to files, there are other Log::Any adapters you can look at.
Also take a look at L<Log::Any::App>.

=head2 How do I debug my CLI script?

To see stack trace on error, you can use L<Devel::Confess>.
Perinci::CmdLine::Base detects if Devel::Confess is loaded and will return the
stack trace for you:

 % perl -d:Confess /path/to/yourscript.pl

or:

 % PERL5OPT='-d:Confess' yourscript.pl

=head1 SEE ALSO

L<Perinci::CmdLine::Manual>

=head1 HOMEPAGE

Please visit the project's homepage at L<https://metacpan.org/release/Perinci-CmdLine>.

=head1 SOURCE

Source repository is at L<https://github.com/perlancar/perl-Perinci-CmdLine>.

=head1 BUGS

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

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.

=head1 AUTHOR

perlancar <perlancar@cpan.org>

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2015 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.

=cut
