Elixir

v1.2.6

Elixir

Elixir v1.2.6 OptionParser

This module contains functions to parse command line options.

Summary

Types

argv()
errors()
options()
parsed()

Functions

next(argv, opts \\ [])

Low-level function that parses one option

parse(argv, opts \\ [])

Parses argv into a keywords list

parse_head(argv, opts \\ [])

Similar to parse/2 but only parses the head of argv; as soon as it finds a non-switch, it stops parsing

split(string)

Splits a string into argv chunks

to_argv(enum)

Receives a key-value enumerable and converts it to argv

Types

argv() 
argv() :: [String.t]
errors() 
errors() :: [{String.t, String.t | nil}]
options() 
options() :: [switches: Keyword.t, strict: Keyword.t, aliases: Keyword.t]
parsed() 
parsed() :: Keyword.t

Functions

next(argv, opts \\ []) 
next(argv, options) ::
  {:ok, key :: atom, value :: term, argv} |
  {:invalid, String.t, String.t | nil, argv} |
  {:undefined, String.t, String.t | nil, argv} |
  {:error, argv}

Low-level function that parses one option.

It accepts the same options as parse/2 and parse_head/2 as both functions are built on top of next. This function may return:

  • {:ok, key, value, rest} - the option key with value was successfully parsed

  • {:invalid, key, value, rest} - the option key is invalid with value (returned when the switch type does not match the one given via the command line)

  • {:undefined, key, value, rest} - the option key is undefined (returned in strict mode when the switch is unknown)

  • {:error, rest} - there are no switches at the top of the given argv
parse(argv, opts \\ []) 
parse(argv, options) :: {parsed, argv, errors}

Parses argv into a keywords list.

It returns a three-element tuple as follows:

  1. parsed switches,
  2. remaining arguments,
  3. invalid options.

Examples 

iex> OptionParser.parse(["--debug"])
{[debug: true], [], []}

iex> OptionParser.parse(["--source", "lib"])
{[source: "lib"], [], []}

iex> OptionParser.parse(["--source-path", "lib", "test/enum_test.exs", "--verbose"])
{[source_path: "lib", verbose: true], ["test/enum_test.exs"], []}

By default, Elixir will try to automatically parse all switches. Switches followed by a value will be assigned the value, as a string. Switches without an argument, like --debug will automatically be set to true.

Note: Elixir also converts the switches to underscore atoms, so --source-path becomes :source_path, to better suit Elixir conventions. This means that option names on the command line cannot contain underscores; such options will be put in the invalid options list.

Switch Definitions

Often it is better to explicitly list the known switches and their formats. The switches can be specified via two alternative options:

  • :switches - defines some switches. An attempt is still made to parse switches that do not appear in the list.

  • :strict - the switches are strict. Any switch that is not specified in the list is returned in the invalid options list.

Note that you should only supply the :switches or :strict option. If you supply both, an error will be raised.

For each switch, the following types are supported:

  • :boolean - marks the given switch as a boolean. Boolean switches never consume the following value unless it is true or false.
  • :integer - parses the switch as an integer.
  • :float - parses the switch as a float.
  • :string - returns the switch as a string.

If a switch can’t be parsed, it is returned in the invalid options list.

The following extra “types” are supported:

  • :keep - keeps duplicated items in the list instead of overriding them.

Note: if you want to use :keep with a non-string type, use a list, e.g. [foo: [:integer, :keep]].

Examples:

iex> OptionParser.parse(["--unlock", "path/to/file"], strict: [unlock: :boolean])
{[unlock: true], ["path/to/file"], []}

iex> OptionParser.parse(["--unlock", "--limit", "0", "path/to/file"],
...>                    strict: [unlock: :boolean, limit: :integer])
{[unlock: true, limit: 0], ["path/to/file"], []}

iex> OptionParser.parse(["--limit", "3"], strict: [limit: :integer])
{[limit: 3], [], []}

iex> OptionParser.parse(["--limit", "xyz"], strict: [limit: :integer])
{[], [], [{"--limit", "xyz"}]}

iex> OptionParser.parse(["--unknown", "xyz"], strict: [])
{[], ["xyz"], [{"--unknown", nil}]}

iex> OptionParser.parse(["--limit", "3", "--unknown", "xyz"],
...>                    switches: [limit: :integer])
{[limit: 3, unknown: "xyz"], [], []}

iex> OptionParser.parse(["--unlock", "path/to/file", "--unlock", "path/to/another/file"], strict: [unlock: :keep])
{[unlock: "path/to/file", unlock: "path/to/another/file"], [], []}

Negation switches

In case a switch is declared as boolean, it may be passed as --no-SWITCH which will set the option to false:

iex> OptionParser.parse(["--no-op", "path/to/file"], switches: [op: :boolean])
{[op: false], ["path/to/file"], []}

Aliases

A set of aliases can be given as options too:

iex> OptionParser.parse(["-d"], aliases: [d: :debug])
{[debug: true], [], []}
parse_head(argv, opts \\ []) 
parse_head(argv, options) :: {parsed, argv, errors}

Similar to parse/2 but only parses the head of argv; as soon as it finds a non-switch, it stops parsing.

See parse/2 for more information.

Example 

iex> OptionParser.parse_head(["--source", "lib", "test/enum_test.exs", "--verbose"])
{[source: "lib"], ["test/enum_test.exs", "--verbose"], []}

iex> OptionParser.parse_head(["--verbose", "--source", "lib", "test/enum_test.exs", "--unlock"])
{[verbose: true, source: "lib"], ["test/enum_test.exs", "--unlock"], []}
split(string) 
split(String.t) :: argv

Splits a string into argv chunks.

Examples 

iex> OptionParser.split("foo bar")
["foo", "bar"]

iex> OptionParser.split("foo \"bar baz\"")
["foo", "bar baz"]
to_argv(enum) 
to_argv(Enumerable.t) :: argv

Receives a key-value enumerable and converts it to argv.

Keys must be atoms. Keys with nil value are discarded, boolean values are converted to --key or --no-key and all other values are converted using to_string/1.

Examples 

iex>  OptionParser.to_argv([foo_bar: "baz"])
["--foo-bar", "baz"]

iex>  OptionParser.to_argv([bool: true, bool: false, discarded: nil])
["--bool", "--no-bool"]