NAME
App::Cmdline - helper for writing command-line applications
VERSION
version 0.1.2
SYNOPSIS
In your command-line script, e.g. in myapp:
use App::myapp;
App::myapp->run;
Such command-line script will be executed, for example, by:
senger@ShereKhan$ myapp --version
senger@ShereKhan$ myapp --check
senger@ShereKhan$ myapp -c
In your module that does the full job you are implementing, e.g. in
App/myapp.pm:
package App::myapp;
use parent 'App::Cmdline';
# Define your own options, and/or add some predefined sets.
sub opt_spec {
my $self = shift;
return $self->check_for_duplicates (
[ 'check|c' => "only check the configuration" ],
$self->composed_of (
'App::Cmdline::Options::Basic',
'App::Cmdline::Options::DB',
)
);
}
# The main job is implemented here
use Data::Dumper;
sub execute {
my ($self, $opt, $args) = @_;
print STDERR "Started...\n" unless $opt->quiet;
print STDOUT 'Options ($opt): ' . Dumper ($opt);
print STDOUT 'Arguments ($args): ' . Dumper ($args);
...
}
DESCRIPTION
This module helps to write command-line applications, especially if they
need to be fed by some command-line options and arguments. It extends
the App::Cmd::Simple module by adding the ability to use several
predefined sets of options that many real command-line applications use
and need anyway. For example, in most applications you need a way how to
print its version or how to provide a decent help text. Once (or if) you
agree with the way how it is done here, you can spend much less time
with the almost-always-repeating options.
Your module (representing the application you are writing) should
inherit from this module and implement, at least, the method opt_spec
(optionally) and the method execute (mandatory).
METHODS
In order to use the ability of composing list of options from the
existing sets of predefined options (which is, after all, the main
*raison d'être* of this module) use the method composed_of. And to find
out that various predefined sets of options do not step on each other
toes, use the method check_for_duplicates.
When writing a subclass of App::Cmdline, there are only a few methods
that you might want to overwrite (except for execute that you must
overwrite). Below are those that may be of your interest, or those that
are implemented here slightly differently from the App::Cmd::Simple.
Summary of methods
Methods that you must overwrite
execute()
Methods that you should overwrite
opt_spec()
Methods that you may overwrite
usage_desc()
validate_args()
usage_error()
getopt_conf()
...
Methods that you just call
composed_of()
check_for_duplicates()
usage_error()
opt_spec
This method returns a list with option definitions, each element being
an arrayref. This returned list is passed (starting as its second
argument) to "describe_options" from Getopt::Long::Descriptive. You need
to check the documentation on how to specify options, but mainly each
element is a pair of *option specification* and the *help text for this
option*. For example:
sub opt_spec {
my $self = shift;
return
[ 'latitude|y=s' => "geographical latitude" ],
[ 'longitude|x=s' => "geographical longitude" ],
;
}
The *option specification* (the first part of each pair) is how the
option can appear on the command-line, in its short or long version, if
it takes a value, how/if can be repeated, etc.
The option elements can be richer. Another useful piece of the option
definition is its default value - see an example of it in "OPTIONS" in
App::Cmdline::Options::DB.
The example above, however, does not add anything new to the
App::Cmd::Simple. Specifying the options this way, you could (and
probably should) inherit directly from the App::Cmd::Simple without
using "App::Cmdline". Therefore, let's have another example:
sub opt_spec {
my $self = shift;
return
[ 'latitude|y=s' => "geographical latitude" ],
[ 'longitude|x=s' => "geographical longitude" ],
$self->composed_of (
'App::Cmdline::Options::Basic',
'App::Cmdline::Options::DB',
);
}
In this example, your command-line application will recognize the same
options (latitude and longitude) as before and, additionally, all
options that were predefined in the *role* classes
App::Cmdline::Options::Basic and App::Cmdline::Options::DB. See more
about these classes in "PREDEFINED SETS OF OPTIONS";
If not overridden, it returns an empty list.
composed_of
The core method of this module. You call it with a list of names of the
classes that are able to give back a list of predefined options that you
may instantly use. The classes are not only specifying their options
but, for some options, they also do something. For example, the "-h"
option (defined in App::Cmdline::Options::Basic) prints the usage and
exits.
This distribution contains few such classes (see the "PREDEFINED SETS OF
OPTIONS"). Later, they may be published other similar classes providing
different sets of options.
The method returns a list of options definitions that is suitable for
including in the returned values of the opt_spec method (as it was shown
in the example above). The returned value should always be used only at
the end, after your application specifies its own options (those that
are not coming from any predefined set). This is because the last
element of the returned list is a hashref containing configuration for
the Getopt::Long - as described in the Getopt::Long::Descriptive.
Therefore, if you need to call this method more than once or not at the
end, perhaps because you wish to see the options in the help usage in a
different order, you need to remove its last element before you add
anything after that:
sub opt_spec {
my $self = shift;
my @db_options = $self->composed_of ('App::Cmdline::Options::DB');
pop @db_options;
return
@db_options,
[ 'latitude|y=s' => "geographical latitude" ],
[ 'longitude|x=s' => "geographical longitude" ],
$self->composed_of (
'App::Cmdline::Options::Basic',
);
}
The last example looks a bit inconvenient. And you do not need to do it
that way - because the "composed_of" method accepts also any arrayrefs,
ignoring them and just passing them to its return value. That's why you
really can call this method only once and not to be bothered with the
hashref at the end. Here is an example how you can combine class names
(predefined sets) with your own option specification and/or usage
separators (the empty arrayrefs):
return
[ 'check|c' => "only check the configuration" ],
[],
$self->composed_of (
'App::Cmdline::Options::DB',
[ 'show|s' => "show database access properties" ],
[],
'App::Cmdline::Options::Basic',
);
which - when called with the -h option - shows this nicely formatted
usage:
Usage: myapp [short or long options, not bundled]
-c --check only check the configuration
--dbname database name
--dbhost hostname hosting database
--dbport database port number
--dbuser user name to access database
--dbpasswd password to access database
--dbsocket UNIX socket accessing the database
-s --show show database access properties
-h display a short usage message
-v --version display a version
check_for_duplicates
When you are composing options from more sets, it is worth to check
whether, unintentionally, some options are not duplicated. It can be
done by this method that gets the list of options definitions, checks it
(warning if any duplicate was found, and returning the same list
unchanged. It can, therefore, be used like this:
sub opt_spec {
my $self = shift;
return $self->check_for_duplicates (
[ 'latitude|y=s' => "geographical latitude" ],
[ 'longitude|x=s' => "geographical longitude" ],
$self->composed_of (
'App::Cmdline::Options::Basic',
'App::Cmdline::Options::DB',
)
);
}
getopt_conf
The machinery behind the scene is done by the Getopt::Long module. This
module can be configured by a list of strings in order to achieve a
different interpretation of the command-line options. Such as to treat
them case-insensitively, or to allow them to be bundled together. For
the recognized strings you need to read the "Configuring Getopt::Long"
in Getopt::Long. Here is shown how and when to use them.
The "App::Cmdline" provides a default set of strings:
sub getopt_conf {
return [
'no_bundling',
'no_ignore_case',
'auto_abbrev',
];
}
If you need it differently, override the getopt_conf method, returning
an arrayref with configuration strings you want. Here are the examples
showing the difference. Using the default configuration and having the
following options:
sub opt_spec {
my $self = shift;
return
[ 'xpoint|x' => 'make an X point'],
[ 'ypoint|y' => 'make a Y point'],
[],
$self->composed_of (
'App::Cmdline::Options::Basic',
);
}
I can run (and get dumped the recognized options and arguments in the
"execute" method:
senger@ShereKhan2:myapp -x -y
Executing...
Options ($opt): $VAR1 = bless( {
'xpoint' => 1,
'ypoint' => 1
}, 'Getopt::Long::Descriptive::Opts::__OPT__::2' );
Arguments ($args): $VAR1 = [];
You can see that both options, "-x" and "-y", were recognized. But if I
bundle them (and by default, the bundling is disabled), I get no
recognized options; instead they will be shown as arguments (arguments
being everything what remained not recognized on the command-line):
senger@ShereKhan2:myapp -x -y
Executing...
Options ($opt): $VAR1 = bless( {}, 'Getopt::Long::Descriptive::Opts::__OPT__::2' );
Arguments ($args): $VAR1 = [ '-xy' ];
But if I change the configuration by implementing:
sub getopt_conf {
return [ 'bundling' ];
}
the bundled options are now recognized as options (and no argument
reminded):
senger@ShereKhan2:myapp -xy
Executing...
Options ($opt): $VAR1 = bless( {
'xpoint' => 1,
'ypoint' => 1
}, 'Getopt::Long::Descriptive::Opts::__OPT__::2' );
Arguments ($args): $VAR1 = [];
usage_desc
The returned value from this method will be used as the first line of
the usage message. The full usage is returned by another method,
"usage", that you usually do not overwrite because its default behaviour
is to create a reasonable summary from the help texts you provided in
the opt_spec method and, possibly, by this "usage_desc" method.
Behind the scene, the returned string is interpreted by the
Getopt::Long::Descriptive which accepts also few special constructs:
* %c will be replaced with what "Getopt::Long::Descriptive" thinks is
the program name (it is computed from $0).
* %o will be replaced with a list of the short options, as well as the
text "[long options...]" if any have been defined.
* Literal % characters will need to be written as %%, just like with
sprintf.
By default, the "App::Cmdline" returns slightly different usage
description depending on the bundling configuration option (see
getopt_conf): if the bundling is disabled, the bundle of all short
options is not shown. Often, you want to use whatever "App::Cmdline"
returns plus what you wish to add on the first line of the usage. For
example:
sub usage_desc {
return shift->SUPER::usage_desc() . ' ...and anything else';
}
validate_args
Originally, this method was meant to check (validate) the command-line
arguments (remember that arguments are whatever remains on the
command-line after options defined in the opt_spec method have been
processed). The options themselves could be already validated by various
subroutines and attributes given in the option specifications (as
described, sometimes only vaguely, in the Getopt::Long::Descriptive).
But sometimes, it is useful to have all validation, of options and of
arguments, in one place - so we have this method.
The method gets two parameters, $opt and $args. The first one is an
instance of Getopt::Long::Descriptive::Opts giving you access to all
existing options, using their names (as were defined in opt_spec) as the
access methods. The second parameter is an arrayref containing all
remaining arguments on the command-line.
*Important:* Some predefined sets of options (see the "PREDEFINED SETS
OF OPTIONS") do also some checking (or other actions, like printing the
version and exiting) and this checking is invoked from the
"App::Cmdline"'s validate_args method. Therefore, it is strongly
recommended that if you overwrite this method, you also call the SUPER:
sub validate_args {
my ($self, $opt, $args) = @_;
$self->SUPER::validate_args ($opt, $args);
if ($opt->number and scalar @$args != $opt->number) {
$self->usage_error ("Option --number does not correspond with the number of arguments");
}
}
senger@ShereKhan2:myapp -n 2 a b c
Error: Option --number does not correspond with the number of arguments
Usage: myapp [short or long options, not bundled] <some arguments...>
-n --number expected number of args
-h display a short usage message
-v --version display a version
The example also shows calling the method "usage_error". Unless you
overwrite also this method, it prints the given error message together
with the usage and dies.
execute
Last but definitely not least. You have to implement this method and put
here whatever your command-line application is supposed to do.
The method gets two parameters, $opt and $args. The first one is an
instance of Getopt::Long::Descriptive::Opts giving you access to all
existing options, using their names (as were defined in opt_spec) as the
access methods. The second parameter is an arrayref containing all
remaining arguments on the command-line.
sub execute {
my ($self, $opt, $args) = @_;
if ($opt->crystal eq 'ball') {
print ask_ball ($args->[0]);
} else {
die "All is vanity...\n"
unless $opt->godess;
}
}
PREDEFINED SETS OF OPTIONS
The predefined sets of options are represented by classes that are
considered rather "roles". You do not extend them (inherit from them)
but you just use them (by naming them in the method composed_of).
This distribution bundles several of such classes. See their own
documentation to find out what options they provide. Here is just a
quick summary:
App::Cmdline::Options::Basic
Provides basic options (help and version).
App::Cmdline::Options::ExtBasic
Provides the same options as in App::Cmdline::Options::Basic and
adds options for richer documentation.
App::Cmdline::Options::DB
Provides options for accessing a database (user authentication, host
and port name, etc.).
App::Cmdline::Options::ExtDB
Provides the same options as in App::Cmdline::Options::DB and adds
an option for showing what values were given by the database-related
options.
How to create a new predefined set
You may wish to create a new set of options if you want to re-use them.
For application-specific options, used only once, you do not need to
have a predefined set, you just specify them directly in the opt_spec
method.
The classes that can be used as the predefined sets of options do not
inherit from any common class (so far, there was no need for it) -
unless one extends another one (as is the case of
App::Cmdline::Options::ExtBasic). It is, however, recommended, to use
the namespace *App::Cmdline::Options::* - just to find them easier on
CPAN.
Each of these classes should implement up to two methods:
get_opt_spec
Strictly speaking, it is not mandatory, but without this method the
class can hardly predefine any new options. The method should return
a list of arrayrefs, suitable to be consumed by the opt_spec method.
For example (taken from the App::Cmdline::Options::Basic):
sub get_opt_spec {
return
[ 'h' => "display a short usage message" ],
[ 'version|v' => "display a version" ];
}
validate_opts
This method, if exists, will be called from the validate_args
method. Its purpose is to do something with the options belonging to
(predefined by) this class.
It gets four parameters, $app (the class name of your application),
$caller (who is calling), $opts (an object allowing to access all
options) and $args (an arrayref with the remaining arguments from
the command-line).
If it finds an error, it usually dies by calling
$caller->"usage_error".
AUTHOR
Martin Senger <martin.senger@gmail.com>
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 by Martin Senger, CBRC - KAUST
(Computational Biology Research Center - King Abdullah University of
Science and Technology) All Rights Reserved.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.