NAME
Getopt::ArgParse - Parsing command line arguments with a richer and more
user-friendly API interface, similar to python's argpare but with
perlish extras.
In particular, the modules provides the following features:
- generating usage messages
- storing parsed arg values in an object, which can be also used to
load configuration values from files and therefore the ability for
applications to combine configurations in a single interface
- A more user-friendly interface to specify arguments, such as
argument types, argument values split, etc.
- Subcommand parsing, such svn <command>
- Supporting both flag based optional arguments and positional arguments
VERSION
version 1.0.3
SYNOPSIS
use Getopt::ArgParse;
$ap = Getopt::ArgParse->new_parser(
prog => 'MyProgramName',
description => 'This is a program',
epilog => 'This appears at the bottom of usage',
);
# Parse an option: '--foo value' or '-f value'
$ap->add_arg('--foo', '-f', required => 1);
# Parse a boolean: '--bool' or '-b' using a different name from
# the option
$ap->add_arg('--bool', '-b', type => 'Bool', dest => 'boo');
# Parse a positonal option.
# But in this case, better using subcommand. See below
$ap->add_arg('command', required => 1);
# $ns is also accessible via $ap->namespace
$ns = $ap->parse_args(split(' ', 'test -f 1 -b'));
say $ns->command; # 'test'
say $ns->foo; # false
say $ns->boo; # false
say $ns->no_boo; # true - 'no_' is added for boolean options
# You can continue to add arguments and parse them again
# $ap->namespace is accumulatively populated
# Parse an Array type option and split the value into an array of values
$ap->add_arg('--emails', type => 'Array', split => ',');
$ns = $ap->parse_args(split(' ', '--emails a@perl.org,b@perl.org,c@perl.org'));
# Because this is an array option, this also allows you to specify the
# option multiple times and splitting
$ns = $ap->parse_args(split(' ', '--emails a@perl.org,b@perl.org --emails c@perl.org'));
# Below will print: a@perl.org|b@perl.org|c@perl.org|a@perl.org|b@perl.org|c@perl.org
# Because Array types are appended
say join('|', $ns->emails);
# Parse an option as key,value pairs
$ap->add_arg('--param', type => 'Pair', split => ',');
$ns = $ap->parse_args(split(' ', '--param a=1,b=2,c=3'));
say $ns->param->{a}; # 1
say $ns->param->{b}; # 2
say $ns->param->{c}; # 3
# You can use choice to restrict values
$ap->add_arg('--env', choices => [ 'dev', 'prod' ],);
# or use case-insensitive choices
# Override the previous option with reset
$ap->add_arg('--env', choices_i => [ 'dev', 'prod' ], reset => 1);
# or use a coderef
# Override the previous option
$ap->add_args(
'--env',
choices => sub {
die "--env invalid values" if $_[0] !~ /^(dev|prod)$/i;
},
reset => 1,
);
# subcommands
$ap->add_subparsers(title => 'subcommands'); # Must be called to initialize subcommand parsing
$list_parser = $ap->add_parser(
'list',
help => 'List directory entries',
description => 'A multiple paragraphs long description.',
);
$list_parser->add_args(
[
'--verbose', '-v',
type => 'Count',
help => 'Verbosity',
],
[
'--depth',
help => 'depth',
],
);
$ns = $ap->parse_args(split(' ', 'list -v'));
say $ns->current_command(); # current_command stores list,
# Don't use this name for your own option
$ns =$ap->parse_args(split(' ', 'help list')); # This will print the usage for the list command
# help subcommand is automatically added for you
say $ns->help_command(); # list
# Copy parsing
$common_args = Getopt::ArgParse->new_parser();
$common_args->add_args(
[
'--dry-run',
type => 'Bool',
help => 'Dry run',
],
);
$sp = $ap->add_parser(
'remove',
aliases => [qw(rm)], # prog remove or prog rm
parents => [ $command_args ], # prog rm --dry-run
);
# Or copy explicitly
$sp = $ap->add_parser(
'copy',
aliases => [qw(cp)], # prog remove or prog rm
);
$sp->copy_args($command_parser); # You can also copy_parsers() but in this case
# $common_parser doesn't have subparsers
DESCRIPTIOIN
Getopt::ArgParse, Getopt::ArgParse::Parser and related classes together
aim to provide user-friendly interfaces for writing command-line
interfaces. A user should be able to use it without looking up the
document most of the time. It allows applications to define argument
specifications and it will parse them out of @AGRV by default or a
command line if provided. It implements both optional arguments, using
Getopt::Long for parsing, and positional arguments. The class also
generates help and usage messages.
The parser has a namespace property, which is an object of
ArgParser::Namespace. The parsed argument values are stored in this
namespace property. Moreover, the values are stored accumulatively when
parse_args() is called multiple times.
Though inspired by Python's argparse and names and ideas are borrowed
from it, there is a lot of difference from the Python one.
Getopt::ArgParser::Parser
This is the underlying parser that does the heavylifting.
Getopt::ArgParse::Parser is a Moo class.
Constructor
my $parser = Getopt::ArgParse->new_parser(
help => 'short description',
description => 'long description',
);
The former calls Getopt::ArgParser::Parser->new to create a parser
object. The parser constructor accepts the following parameters.
All parsers are created with a predefined Bool option --help|-h. The
program can choose to reset it, though.
* prog
The program's name. Default $0.
* help
A short description of the program.
* description
A long description of the program.
* namespace
An object of Getopt::ArgParse::Namespace. An empty namespace is
created if not provided. The parsed values are stored in it, and
they can be refered to by their argument names as the
namespace's properties, e.g. $parser->namespace->boo. See also
Getopt::ArgParse::Namespace
* parser_configs
The Getopt::Long configurations. See also Getopt::Long
* parents
Parent parsents, whose argument and subparser specifications the
new parser will copy. See copy() below
* error_prefix
Customize the message prefixed to error messages thrown by
Getop::ArgParse, default to 'Getopt::ArgParse: '
* print_usage_if_help
Set this to false to not display usage messages even if --help
is on or the subcommand help is called. The default behavior is
to display usage messages if help is set.
add_arg, add_argument, add_args, and add_arguments
$parser->add_args(
[ '--foo', required => 1, type => 'Array', split => ',' ],
[ 'boo', required => 1, nargs => '+' ],
);
The object method, arg_arg or the longer version add_argument, defines
the specfication of an argument. It accepts the following parameters.
add_args or add_arguments() is to add multiple multiple arguments.
* name or flags
Either a name or a list of option strings, e.g. foo or -f,
--foo.
If dest is not specified, the name or the first option without
leading dashes will be used as the name for retrieving values.
If a name is given, this argument is a positional argument.
Otherwise, it's an option argument.
Hyphens can be used in names and flags, but they will be
replaced with underscores '_' when used as option names. For
example:
$parser->add_argument( [ '--dry-run', type => 'Bool' ]);
# command line: prog --dry-run
$parser->namespace->dry_run; # The option's name is dry_run
A name or option strings are following by named paramters.
* dest
The name of the attribute to be added to the namespace populated
by parse_args().
* type => $type
Specify the type of the argument. It can be one of the following
values:
* Scalar
The option takes a scalar value.
* Array
The option takes a list of values. The option can appear
multiple times in the command line. Each value is
appended to the list. It's stored in an arrayref in the
namespace.
* Pair
The option takes a list of key-value pairs separated by
the equal sign '='. It's stored in a hashref in the
namespace.
* Bool
The option does not take an argument. It's set to true
if the option is present or false otherwise. A 'no_bool'
option is also available, which is the negation of
bool().
For example:
$parser->add_argument('--dry-run', type => 'Bool');
$ns = $parser->parse_args(split(' ', '--dry-run'));
print $ns->dry_run; # true
print $ns->no_dry_run; # false
* Count
The option does not take an argument and its value will
be incremented by 1 every time it appears on the command
line.
* split
split should work with types 'Array' and 'Pair' only.
split specifies a string by which to split the argument string
e.g. if split => ',', a,b,c will be split into [ 'a', 'b', 'c'
].When split works with type 'Pair', the parser will split the
argument string and then parse each of them as pairs.
* choices or choices_i
choices specifies a list of the allowable values for the
argument or a subroutine that validates input values.
choices_i specifies a list of the allowable values for the
argument, but case insenstive, and it doesn't allow to use a
subroutine for validation.
Either choices or chioces_i can be present or completely
omitted, but not both at the same time.
* default
The value produced if the argument is absent from the command
line.
Only one value is allowed for scalar argument types: Scalar,
Count, and Bool.
* required
Whether or not the command-line option may be omitted (optionals
only). This has no effect on types 'Bool' and 'Count'. An
optional option is marked by the question mark ? in the
generated usage, e.g. --help, -h ? show this help message and
exit
This parameter is ignored for Bool and Count types for they will
already have default values.
* help
A brief description of what the argument does.
* metavar
A name for the argument in usage messages.
* reset
Set reset to override the existing definition of an option. This
will clear the value in the namspace as well.
* nargs - Positional option only
This only instructs how many arguments the parser consumes. The
program still needs to specify the right type to achieve the
desired result.
* n
1 if not specified
* ?
1 or 0
* +
1 or more
* *
0 or many. This will consume the rest of arguments.
parse_args
$namespace = $parser->parse_args(@command_line);
This object method accepts a list of arguments or @ARGV if unspecified,
parses them for values, and stores the values in the namespace object.
A few things may be worth noting about parse_args().
First, parsing for Optional Arguments is done by Getopt::Long
Second, parsing for positional arguments takes place after that for
optional arguments. It will consume what's still left in the command
line.
Finally, the Namespace object is accumulatively poplulated. If
parse_args() is called multiple times to parse a number of command
lines, the same namespace object is accumulatively populated. For Scalar
and Bool options, this means the previous value will be overwrittend.
For Pair and Array options, values will be appended. And for a Count
option, it will add on top of the previous value.
In face, the program can choose to pass a already populated namespace
when creating a parser object. This is to allow the program to pre-load
values to a namespace from conf files before parsing the command line.
And finally, it does NOT display usage messages if the argument list is
empty. This may be contrary to many other implementations of argument
parsing.
argv
@argv = $parser->argv; # called after parse_args
Call this after parse_args() is invoked to get the unconsumed arguments.
It's up to the application to decide what to do if there is a surplus of
arguments.
The Namespace Object
The parsed values are stored in a namespace object. Any class with the
following three methods:
* A constructor new()
* set_attr(name => value)
* get_attr(name)
can be used as the Namespace class.
The default one is Getopt::ArgParse::Namespace. It uses autoload to
provide a readonly accessor method using dest names to access parsed
values. However, this is not required for user-defined namespace. So
within the implementation, $namespace->get_attr($dest) should always be
used.
Subcommand Support
Note only ne level of subcommand parsing is supported. Subcommands
cannot have subcommands.
Call add_subparsers() first to initialize the current parser for
subcommand support. A help subcommand is created as part of the
initialization. The help subcommand has the following options:
positional arguments: COMMAND ? Show the usage for this command
optional arguments: --help, -h ? show this help message and exit
--all, -a ? Show the full usage
Call add_parser() to add a subparser for each subcommand. Use the parser
object returned by add_parser() to add the options to the subcommand.
Once subcommand support is on, if the first argument is not a flag, i.e.
starting with a dash '-', the parser's parse_args() will treat it as a
subcommand. Otherwise, the parser parses for the defined arguments.
The namespace's current_command() will contain the subcommand after
parsing successfully.
Unlike arguments, subparsers cannot be reset.
add_subparsers
$parser->add_subparsers(
title => 'Subcommands',
description => 'description about providing subcommands',
);
add_subparsers must be called to initialize subcommand support.
* title
A title message to mark the beginning of subcommand usage in the
usage message
* description
A general description appearing about the title
add_parser
$subparser = $parser->add_parser(
'list',
aliases => [qw(ls)],
help => 'short description',
description => 'a long one',
parents => [ $common_args ], # inherit common args from
# $common_args
);
* $command
The first argument is the name of the new command.
* help
A short description of the subcommand.
* description
A long description of the subcommand.
* aliases
An array reference containing a list of command aliases.
* parents
An array reference containing a list of parsers whose
specification will be copied by the new parser.
get_parser
$subparser = $parser->get_parser('ls');
Return the parser for parsing the $alias command if exsist.
Copying Parsers
A parser can copy argument specification or subcommand specifciation for
existing parsers. A use case for this is that the program wants all
subcommands to have a command set of arguments.
copy_args
$parser->copy_args($common_args_parser);
Copy argument specification from the $parent parser
copy_parsers
$parser->copy_parsers($common_args_parser);
Copy parser specification for subcommands from the $parent parser
copy
$parser->copy($common_args_parser);
Copy both arguments and subparsers.
Usage Messages and Related Methods
format_usage
$usage = $parser->format_usage;
Return the formated usage message for the whole program in an array
reference.
print_usage
$parser->print_usage;
Print the usage mesage returned by format_usage().
format_command_usage
$usage = $parser->format_command_usage($subcommand);
Return the formated usage message for the command in an array reference.
print_command_usage
$parser->print_command_usage($subcommand);
Print the usage message returned by format_command_usage(). If $command
is not given, it will first try to use $self->namespace->help_command,
which will be present for the help subcommand, and then
$self->namespace->current_command.
SEE ALSO
Getopt::Long
Python's argparse
AUTHOR
Mytram <mytram2@gmail.com> (original author)
COPYRIGHT AND LICENSE
This software is Copyright (c) 2014 by Mytram.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)