Provided by: lua-argparse_0.5.0-1_all bug

NAME

       argparse - argparse tutorial

       Contents:

CREATING AND USING PARSERS

       The  argparse  module  is a function which, when called, creates an instance of the Parser
       class.

          -- script.lua
          local argparse = require "argparse"
          local parser = argparse()

       parser is now an empty parser which does not  recognize  any  command  line  arguments  or
       options.

   Parsing command line arguments
       :parse([args])  method  of  the  Parser class returns a table with processed data from the
       command line or args array.

          local args = parser:parse()
          print(args)  -- Assuming print is patched to handle tables nicely.

       When executed, this script prints {} because the parser  is  empty  and  no  command  line
       arguments were supplied.

   Error handling
       If  the provided command line arguments are not recognized by the parser, it will print an
       error message and call os.exit(1).

          $ lua script.lua foo

          Usage: script.lua [-h]

          Error: too many arguments

       If halting the program is undesirable, :pparse([args]) method should be used.  It  returns
       boolean flag indicating success of parsing and result or error message.

       An error can raised manually using :error() method.

          parser:error("manual argument validation failed")

          Usage: script.lua [-h]

          Error: manual argument validation failed

   Help option
       As  the  automatically  generated usage message states, there is a help option -h added to
       any parser by default.

       When a help option is used, parser will print a help message and call os.exit(0).

          $ lua script.lua -h

          Usage: script.lua [-h]

          Options:
             -h, --help            Show this help message and exit.

   Typo autocorrection
       When an option is not recognized by the parser, but there is  an  option  with  a  similar
       name, a suggestion is automatically added to the error message.

          $ lua script.lua --hepl

          Usage: script.lua [-h]

          Error: unknown option '--hepl'
          Did you mean '--help'?

   Configuring parsers
       Parsers  have  several  properties  affecting their behavior. For example, description and
       epilog properties set the text to be displayed in the help message after the usage message
       and  after  the  listings  of  options and arguments, respectively. Another is name, which
       overwrites the name of the program which is used in the usage message  (default  value  is
       inferred from command line arguments).

       There  are  several ways to set properties. The first is to chain setter methods of Parser
       object.

          local parser = argparse()
             :name "script"
             :description "A testing script."
             :epilog "For more info, see http://example.com"

       The second is to call a parser with a table containing some properties.

          local parser = argparse() {
             name = "script",
             description = "A testing script.",
             epilog "For more info, see http://example.com."
          }

       Finally, name. description and epilog properties can be passed as arguments when calling a
       parser.

          local parser = argparse("script", "A testing script.", "For more info, see http://example.com.")

ADDING AND CONFIGURING ARGUMENTS

       Positional  arguments  can  be  added using :argument(name, description, default, convert,
       args) method. It returns an Argument instance, which can be configured in the same way  as
       Parsers. The name property is required.

          parser:argument "input"

          $ lua script.lua foo

          {
             input = "foo"
          }

       The data passed to the argument is stored in the result table at index input because it is
       the argument's name. The index can be changed using target property.

   Setting number of consumed arguments
       args property sets how many command line arguments the argument  consumes.  Its  value  is
       interpreted as follows:

                      ┌─────────────────────────────────┬─────────────────────────┐
                      │Value                            │ Interpretation          │
                      ├─────────────────────────────────┼─────────────────────────┤
                      │Number N                         │ Exactly N arguments     │
                      ├─────────────────────────────────┼─────────────────────────┤
                      │String  A-B,  where  A and B are │ From A to B arguments   │
                      │numbers                          │                         │
                      ├─────────────────────────────────┼─────────────────────────┤
                      │String N+, where N is a number   │ N or more arguments     │
                      └─────────────────────────────────┴─────────────────────────┘

                      │String ?                         │ An optional argument    │
                      ├─────────────────────────────────┼─────────────────────────┤
                      │String *                         │ Any number of arguments │
                      ├─────────────────────────────────┼─────────────────────────┤
                      │String +                         │ At least one argument   │
                      └─────────────────────────────────┴─────────────────────────┘

       If more than one argument can be consumed, a table is used to store the data.

          parser:argument("pair", "A pair of arguments.")
             :args(2)
          parser:argument("optional", "An optional argument.")
             :args "?"

          $ lua script.lua foo bar

          {
             pair = {"foo", "bar"}
          }

          $ lua script.lua foo bar baz

          {
             pair = {"foo", "bar"},
             optional = "baz"
          }

ADDING AND CONFIGURING OPTIONS

       Options can be added using  :option(name,  description,  default,  convert,  args,  count)
       method. It returns an Option instance, which can be configured in the same way as Parsers.
       The name property is required. An option can have several aliases, which  can  be  set  as
       space separated substrings in its name or by continuously setting name property.

          -- These lines are equivalent:
          parser:option "-f" "--from"
          parser:option "-f --from"

          $ lua script.lua --from there
          $ lua script.lua --from=there
          $ lua script.lua -f there
          $ lua script.lua -fthere

          {
             from = "there"
          }

       For  an  option,  default  index  used to store arguments passed to it is the first "long"
       alias (an alias starting with two control characters, typically hyphens) or just the first
       alias,  without  control  characters.  Hyphens  in  the  default  index  are replaced with
       underscores. In the following table it is assumed that local  args  =  parser:parse()  has
       been executed.

                          ┌─────────────────┬────────────────────────────────┐
                          │Option's aliases │ Location of option's arguments │
                          ├─────────────────┼────────────────────────────────┤
                          │-oargs.o                         │
                          ├─────────────────┼────────────────────────────────┤
                          │-o --outputargs.output                    │
                          ├─────────────────┼────────────────────────────────┤
                          │-s --from-serverargs.from_server               │
                          └─────────────────┴────────────────────────────────┘

       As with arguments, the index can be explicitly set using target property.

   Flags
       Flags are almost identical to options, except that they don't take an argument by default.

          parser:flag("-q --quiet")

          $ lua script.lua -q

          {
             quiet = true
          }

   Control characters
       The  first  characters  of  all aliases of all options of a parser form the set of control
       characters, used to distinguish options from arguments. Typically the set only consists of
       a hyphen.

   Setting number of consumed arguments
       Just as arguments, options can be configured to take several command line arguments.

          parser:option "--pair"
             :args(2)
          parser:option "--optional"
             :args "?"

          $ lua script.lua --pair foo bar

          {
             pair = {"foo", "bar"}
          }

          $ lua script.lua --pair foo bar --optional

          {
             pair = {"foo", "bar"},
             optional = {}
          }

          $ lua script.lua --optional=baz

          {
             optional = {"baz"}
          }

       Note  that  the data passed to optional option is stored in an array. That is necessary to
       distinguish whether the option was invoked without an argument or it was  not  invoked  at
       all.

   Setting number of invocations
       For  options,  it  is  possible  to control how many times they can be used. argparse uses
       count property to set how many times an option can be invoked. The value of  the  property
       is interpreted in the same way args is.

          parser:option("-e --exclude")
             :count "*"

          $ lua script.lua -eFOO -eBAR

          {
             exclude = {"FOO", "BAR"}
          }

       If  an  option  can  be used more than once and it can consume more than one argument, the
       data is stored as an array of invocations, each being an array of arguments.

       As a special case, if an option can be used more than once and it  consumes  no  arguments
       (e.g.  it's  a  flag), than the number of invocations is stored in the associated field of
       the result table.

          parser:flag("-v --verbose", "Sets verbosity level.")
             :count "0-2"
             :target "verbosity"

          $ lua script.lua -vv

          {
             verbosity = 2
          }

MUTUALLY EXCLUSIVE GROUPS

       A group of options can be marked as mutually exclusive using :mutex(option, ...) method of
       the Parser class.

          parser:mutex(
             parser:flag "-q --quiet",
             parser:flag "-v --verbose"
          )

       If more than one element of a mutually exclusive group is used, an error is raised.

          $ lua script.lua -qv

          Usage: script.lua ([-q] | [-v]) [-h]

          Error: option '-v' can not be used together with option '-q'

ADDING AND CONFIGURING COMMANDS

       A  command  is a subparser invoked when its name is passed as an argument. For example, in
       git CLI add, commit, push, etc. are commands. Each command has its own  set  of  arguments
       and options, but inherits options of its parent.

       Commands  can  be added using :command(name, description, epilog) method. Just as options,
       commands can have several aliases.

          parser:command "install i"

       If a command it used, true is stored in the corresponding field of the result table.

          $ lua script.lua install

          {
             install = true
          }

       A typo will result in an appropriate error message.

          $ lua script.lua instal

          Usage: script.lua [-h] <command> ...

          Error: unknown command 'instal'
          Did you mean 'install'?

   Getting name of selected command
       Use command_target property of the parser to store the name of used command in a field  of
       the result table.

          parser:command_target("command")
          parser:command("install")
          parser:command("remove")

          $ lua script.lua install

          {
             install = true,
             command = "install"
          }

   Adding elements to commands
       The  Command  class  is  a  subclass  of the Parser class, so all the Parser's methods for
       adding elements work on commands, too.

          local install = parser:command "install"
          install:argument "rock"
          install:option "-f --from"

          $ lua script.lua install foo --from=bar

          {
             install = true,
             rock = "foo",
             from = "bar"
          }

       Commands have their own usage and help messages.

          $ lua script.lua install

          Usage: script.lua install [-f <from>] [-h] <rock>

          Error: too few arguments

          $ lua script.lua install --help

          Usage: script.lua install [-f <from>] [-h] <rock>

          Arguments:
             rock

          Options:
             -f <from>, --from <from>
             -h, --help            Show this help message and exit.

   Making a command optional
       By default, if a parser has commands, using one of them is obligatory.

          local parser = argparse()
          parser:command "install"

          $ lua script.lua

          Usage: script.lua [-h] <command> ...

          Error: a command is required

       This can be changed using require_command property.

          local parser = argparse()
             :require_command(false)
          parser:command "install"

DEFAULT VALUES

       For elements such as arguments and options, if default property is set to  a  string,  its
       value  is  stored in case the element was not used (if it's not a string, it'll be used as
       init property instead, see actions).

          parser:option("-o --output", "Output file.", "a.out")
          -- Equivalent:
          parser:option "-o" "--output"
             :description "Output file."
             :default "a.out"

          $ lua script.lua

          {
             output = "a.out"
          }

       The existence of a default  value  is  reflected  in  help  message,  unless  show_default
       property is set to false.

          $ lua script.lua --help

          Usage: script.lua [-o <output>] [-h]

          Options:
             -o <output>, --output <output>
                                   Output file. (default: a.out)
             -h, --help            Show this help message and exit.

       Note that invocation without required arguments is still an error.

          $ lua script.lua -o

          Usage: script.lua [-o <output>] [-h]

          Error: too few arguments

   Default mode
       defmode property regulates how argparse should use the default value of an element.

       If  defmode contains u (for unused), the default value will be automatically passed to the
       element if it was not invoked at all. This is the default behavior.

       If defmode contains a (for argument), the default value will be  automatically  passed  to
       the element if not enough arguments were passed, or not enough invocations were made.

       Consider the difference:

          parser:option "-o"
             :default "a.out"
          parser:option "-p"
             :default "password"
             :defmode "arg"

          $ lua script.lua -h

          Usage: script.lua [-o <o>] [-p [<p>]] [-h]

          Options:
             -o <o>                default: a.out
             -p [<p>]              default: password
             -h, --help            Show this help message and exit.

          $ lua script.lua

          {
             o = "a.out"
          }

          $ lua script.lua -p

          {
             o = "a.out",
             p = "password"
          }

          $ lua script.lua -o

          Usage: script.lua [-o <o>] [-p [<p>]] [-h]

          Error: too few arguments

CALLBACKS

   Converters
       argparse can perform automatic validation and conversion on arguments. If convert property
       of an element is a function, it will be applied to all the arguments  passed  to  it.  The
       function  should  return  nil  and,  optionally,  an  error  message if conversion failed.
       Standard tonumber and io.open functions work exactly like that.

          parser:argument "input"
             :convert(io.open)
          parser:option "-t --times"
             :convert(tonumber)

          $ lua script.lua foo.txt -t5

          {
             input = file_object,
             times = 5
          }

          $ lua script.lua nonexistent.txt

          Usage: script.lua [-t <times>] [-h] <input>

          Error: nonexistent.txt: No such file or directory

          $ lua script.lua foo.txt --times=many

          Usage: script.lua [-t <times>] [-h] <input>

          Error: malformed argument 'many'

   Table converters
       If convert property of an element is a table, arguments passed to it will be used as keys.
       If a key is missing, an error is raised.

          parser:argument "choice"
             :convert {
                foo = "Something foo-related",
                bar = "Something bar-related"
             }

          $ lua script.lua bar

          {
             choice = "Something bar-related"
          }

          $ lua script.lua baz

          Usage: script.lua [-h] <choice>

          Error: malformed argument 'baz'

   Actions
   Argument and option actions
       argparse  uses  action  callbacks to process invocations of arguments and options. Default
       actions simply put passed arguments into the result table as a single value or insert into
       an array depending on number of arguments the option can take and how many times it can be
       used.

       A custom action can be set using action property. An action must be a function.  and  will
       be  called  after  each  invocation  of the option or the argument it is assigned to. Four
       arguments are passed: result table, target index in that table, an argument or an array of
       arguments  passed  by  user,  and  overwrite  flag used when an option is invoked too many
       times.

       Converters are applied before actions.

       Initial value to be stored at target index in the result  table  can  be  set  using  init
       property, or also using default property if the value is not a string.

          parser:option("--exceptions"):args("*"):action(function(args, _, exceptions)
             for _, exception in ipairs(exceptions) do
                table.insert(args.exceptions, exception)
             end
          end):init({"foo", "bar"})

          parser:flag("--no-exceptions"):action(function()
             args.exceptions = {}
          end)

          $ lua script.lua --exceptions x y --exceptions z t

          {
             exceptions = {
                "foo",
                "bar",
                "x",
                "y",
                "z",
                "t"
             }
          }

          $ lua script.lua --exceptions x y --no-exceptions

          {
             exceptions = {}
          }

       Actions  can also be used when a flag needs to print some message and exit without parsing
       remaining arguments.

          parser:flag("-v --version"):action(function()
             print("script v1.0.0")
             os.exit(0)
          end)

          $ lua script.lua -v

          script v1.0.0

   Built-in actions
       These actions can be referred to by their string names when setting action property:

                            ┌────────────┬──────────────────────────────────┐
                            │Name        │ Description                      │
                            ├────────────┼──────────────────────────────────┤
                            │store       │ Stores argument or arguments  at │
                            │            │ target index.                    │
                            ├────────────┼──────────────────────────────────┤
                            │store_true  │ Stores true at target index.     │
                            ├────────────┼──────────────────────────────────┤
                            │store_false │ Stores false at target index.    │
                            ├────────────┼──────────────────────────────────┤
                            │count       │ Increments   number   at  target │
                            │            │ index.                           │
                            ├────────────┼──────────────────────────────────┤
                            │append      │ Appends argument or arguments to │
                            │            │ table at target index.           │
                            └────────────┴──────────────────────────────────┘

                            │concat      │ Appends  arguments one by one to │
                            │            │ table at target index.           │
                            └────────────┴──────────────────────────────────┘

       Examples using store_false and concat actions:

          parser:flag("--candy")
          parser:flag("--no-candy"):target("candy"):action("store_false")
          parser:flag("--rain", "Enable rain", false)
          parser:option("--exceptions"):args("*"):action("concat"):init({"foo", "bar"})

          $ lua script.lua

          {
             rain = false
          }

          $ lua script.lua --candy

          {
             candy = true,
             rain = false
          }

          $ lua script.lua --no-candy --rain

          {
             candy = false,
             rain = true
          }

          $ lua script.lua --exceptions x y --exceptions z t

          {
             exceptions = {
                "foo",
                "bar",
                "x",
                "y",
                "z",
                "t"
             },
             rain = false
          }

   Command actions
       Actions for parsers and commands are simply callbacks invoked after parsing,  with  result
       table and command name as the arguments. Actions for nested commands are called first.

          local install = parser:command("install"):action(function(args, name)
             print("Running " .. name)
             -- Use args here
          )

          parser:action(function(args)
             print("Callbacks are fun!")
          end)

          $ lua script.lua install

          Running install
          Callbacks are fun!

MISCELLANEOUS

   Generating and overwriting help and usage messages
       The  usage  and  help  messages  of  parsers and commands can be generated on demand using
       :get_usage() and :get_help() methods, and overridden using help and usage properties.

   Overwriting default help option
       If the property add_help of a parser is set to false, no help option will be added to  it.
       Otherwise, the value of the field will be used to configure it.

          local parser = argparse()
             :add_help "/?"

          $ lua script.lua /?

          Usage: script.lua [/?]

          Options:
             /?                    Show this help message and exit.

   Setting argument placeholder
       For  options  and arguments, argname property controls the placeholder for the argument in
       the usage message.

          parser:option "-f" "--from"
             :argname "<server>"

          $ lua script.lua --help

          Usage: script.lua [-f <server>] [-h]

          Options:
             -f <server>, --from <server>
             -h, --help            Show this help message and exit.

       argname can be an array of placeholders.

          parser:option "--pair"
             :args(2)
             :argname {"<key>", "<value>"}

          $ lua script.lua --help

          Usage: script.lua [--pair <key> <value>] [-h]

          Options:
             --pair <key> <value>
             -h, --help            Show this help message and exit.

   Disabling option handling
       When handle_options property of a parser or a command is set to false, all options will be
       passed verbatim to the argument list, as if the input included double-hyphens.

          parser:handle_options(false)
          parser:argument "input"
             :args "*"
          parser:option "-f" "--foo"
             :args "*"

          $ lua script.lua bar -f --foo bar

          {
             input = {"bar", "-f", "--foo", "bar"}
          }

   Prohibiting overuse of options
       By  default, if an option is invoked too many times, latest invocations overwrite the data
       passed earlier.

          parser:option "-o --output"

          $ lua script.lua -oFOO -oBAR

          {
             output = "BAR"
          }

       Set overwrite property to false to prohibit this behavior.

          parser:option "-o --output"
             :overwrite(false)

          $ lua script.lua -oFOO -oBAR

          Usage: script.lua [-o <output>] [-h]

          Error: option '-o' must be used at most 1 time

   Parsing algorithm
       argparse interprets command line arguments in the following way:

                             ┌──────────┬──────────────────────────────────┐
                             │Argument  │ Interpretation                   │
                             ├──────────┼──────────────────────────────────┤
                             │foo       │ An argument of an  option  or  a │
                             │          │ positional argument.             │
                             ├──────────┼──────────────────────────────────┤
                             │--foo     │ An option.                       │
                             ├──────────┼──────────────────────────────────┤
                             │--foo=bar │ An  option and its argument. The │
                             │          │ option  must  be  able  to  take │
                             │          │ arguments.                       │
                             ├──────────┼──────────────────────────────────┤
                             │-f        │ An option.                       │
                             ├──────────┼──────────────────────────────────┤
                             │-abcdef   │ Letters   are   interpreted   as │
                             │          │ options. If one of them can take │
                             │          │ an  argument,  the  rest  of the │
                             │          │ string is passed to it.          │
                             ├──────────┼──────────────────────────────────┤
                             │--        │ The rest  of  the  command  line │
                             │          │ arguments will be interpreted as │
                             │          │ positional arguments.            │
                             └──────────┴──────────────────────────────────┘

   Property lists
   Parser properties
       Properties that can be set as arguments when calling or constructing  a  parser,  in  this
       order:

                                         ┌────────────┬────────┐
                                         │Property    │ Type   │
                                         ├────────────┼────────┤
                                         │name        │ String │
                                         ├────────────┼────────┤
                                         │description │ String │
                                         ├────────────┼────────┤
                                         │epilog      │ String │
                                         └────────────┴────────┘

       Other properties:

                             ┌────────────────┬────────────────────────────┐
                             │Property        │ Type                       │
                             ├────────────────┼────────────────────────────┤
                             │usage           │ String                     │
                             └────────────────┴────────────────────────────┘

                             │help            │ String                     │
                             ├────────────────┼────────────────────────────┤
                             │require_command │ Boolean                    │
                             ├────────────────┼────────────────────────────┤
                             │handle_options  │ Boolean                    │
                             ├────────────────┼────────────────────────────┤
                             │add_help        │ Boolean or string or table │
                             ├────────────────┼────────────────────────────┤
                             │command_target  │ String                     │
                             └────────────────┴────────────────────────────┘

   Command properties
       Properties  that  can  be set as arguments when calling or constructing a command, in this
       order:

                                         ┌────────────┬────────┐
                                         │Property    │ Type   │
                                         ├────────────┼────────┤
                                         │name        │ String │
                                         ├────────────┼────────┤
                                         │description │ String │
                                         ├────────────┼────────┤
                                         │epilog      │ String │
                                         └────────────┴────────┘

       Other properties:

                             ┌────────────────┬────────────────────────────┐
                             │Property        │ Type                       │
                             ├────────────────┼────────────────────────────┤
                             │target          │ String                     │
                             ├────────────────┼────────────────────────────┤
                             │usage           │ String                     │
                             ├────────────────┼────────────────────────────┤
                             │help            │ String                     │
                             ├────────────────┼────────────────────────────┤
                             │require_command │ Boolean                    │
                             ├────────────────┼────────────────────────────┤
                             │handle_options  │ Boolean                    │
                             ├────────────────┼────────────────────────────┤
                             │action          │ Function                   │
                             ├────────────────┼────────────────────────────┤
                             │add_help        │ Boolean or string or table │
                             ├────────────────┼────────────────────────────┤
                             │command_target  │ String                     │
                             └────────────────┴────────────────────────────┘

   Argument properties
       Properties that can be set as arguments when calling or constructing an argument, in  this
       order:

                                   ┌────────────┬───────────────────┐
                                   │Property    │ Type              │
                                   ├────────────┼───────────────────┤
                                   │name        │ String            │
                                   ├────────────┼───────────────────┤
                                   │description │ String            │
                                   ├────────────┼───────────────────┤
                                   │default     │ Any               │
                                   ├────────────┼───────────────────┤
                                   │convert     │ Function or table │
                                   ├────────────┼───────────────────┤
                                   │args        │ Number or string  │
                                   └────────────┴───────────────────┘

       Other properties:

                                  ┌─────────────┬────────────────────┐
                                  │Property     │ Type               │
                                  ├─────────────┼────────────────────┤
                                  │target       │ String             │
                                  ├─────────────┼────────────────────┤
                                  │defmode      │ String             │
                                  ├─────────────┼────────────────────┤
                                  │show_default │ Boolean            │
                                  ├─────────────┼────────────────────┤
                                  │argname      │ String or table    │
                                  ├─────────────┼────────────────────┤
                                  │action       │ Function or string │
                                  ├─────────────┼────────────────────┤
                                  │init         │ Any                │
                                  └─────────────┴────────────────────┘

   Option and flag properties
       Properties  that can be set as arguments when calling or constructing an option or a flag,
       in this order:

                                   ┌────────────┬───────────────────┐
                                   │Property    │ Type              │
                                   ├────────────┼───────────────────┤
                                   │name        │ String            │
                                   ├────────────┼───────────────────┤
                                   │description │ String            │
                                   ├────────────┼───────────────────┤
                                   │default     │ Any               │
                                   ├────────────┼───────────────────┤
                                   │convert     │ Function or table │
                                   ├────────────┼───────────────────┤
                                   │args        │ Number or string  │
                                   ├────────────┼───────────────────┤
                                   │count       │ Number or string  │
                                   └────────────┴───────────────────┘

       Other properties:

                                  ┌─────────────┬────────────────────┐
                                  │Property     │ Type               │
                                  ├─────────────┼────────────────────┤
                                  │target       │ String             │
                                  ├─────────────┼────────────────────┤
                                  │defmode      │ String             │
                                  ├─────────────┼────────────────────┤
                                  │show_default │ Boolean            │
                                  ├─────────────┼────────────────────┤
                                  │overwrite    │ Booleans           │
                                  ├─────────────┼────────────────────┤
                                  │argname      │ String or table    │
                                  ├─────────────┼────────────────────┤
                                  │action       │ Function or string │
                                  ├─────────────┼────────────────────┤
                                  │init         │ Any                │
                                  └─────────────┴────────────────────┘

       This is a tutorial for argparse, a feature-rich command line parser for Lua.

AUTHOR

       Peter Melnichenko

COPYRIGHT

       2017 - 2015, Peter Melnichenko