Elixir v1.6.4 OptionParser View Source
This module contains functions to parse command line options.
Link to this section Summary
Functions
Low-level function that parses one option
Parses argv
into a keyword list
The same as parse/2
but raises an OptionParser.ParseError
exception if any invalid options are given
Similar to parse/2
but only parses the head of argv
;
as soon as it finds a non-switch, it stops parsing
The same as parse_head/2
but raises an OptionParser.ParseError
exception if any invalid options are given
Splits a string into argv/0
chunks
Receives a key-value enumerable and converts it to argv/0
Link to this section Types
Link to this section Functions
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 this function. This function
may return:
{:ok, key, value, rest}
- the optionkey
withvalue
was successfully parsed{:invalid, key, value, rest}
- the optionkey
is invalid withvalue
(returned when the value cannot be parsed according to the switch type){:undefined, key, value, rest}
- the optionkey
is undefined (returned in strict mode when the switch is unknown){:error, rest}
- there are no switches at the head of the givenargv
Parses argv
into a keyword list.
It returns a three-element tuple with the form {parsed, args, invalid}
, where:
parsed
is a keyword list of parsed switches with{switch_name, value}
tuples in it;switch_name
is the atom representing the switch name whilevalue
is the value for that switch parsed according toopts
(see the “Examples” section for more information)args
is a list of the remaining arguments inargv
as stringsinvalid
is a list of invalid options as{option_name, value}
whereoption_name
is the raw option andvalue
isnil
if the option wasn’t expected or the string value if the value didn’t have the expected type for the corresponding option
Elixir converts switches to underscored atoms, so --source-path
becomes
:source_path
. This is done to better suit Elixir conventions. However, this
means that switches can’t contain underscores and switches that do contain
underscores are always returned in the list of invalid switches.
When parsing, it is common to list switches and their expected types:
iex> OptionParser.parse(["--debug"], switches: [debug: :boolean])
{[debug: true], [], []}
iex> OptionParser.parse(["--source", "lib"], switches: [source: :string])
{[source: "lib"], [], []}
iex> OptionParser.parse(["--source-path", "lib", "test/enum_test.exs", "--verbose"],
...> switches: [source_path: :string, verbose: :boolean])
{[source_path: "lib", verbose: true], ["test/enum_test.exs"], []}
We will explore the valid switches and operation modes of option parser below.
Options
The following options are supported:
:switches
or:strict
- see the “Switch definitions” section below:allow_nonexistent_atoms
- see the “Parsing dynamic switches” section below:aliases
- see the “Aliases” section below
Switch definitions
Switches can be specified via one of two options:
:switches
- defines some switches and their types. This function still attempts to parse switches that are not in this list.:strict
- defines strict switches. Any switch inargv
that is not specified in the list is returned in the invalid options list.
Both these options accept a keyword list of {name, type}
tuples where name
is an atom defining the name of the switch and type
is an atom that
specifies the type for the value of this switch (see the “Types” section below
for the possible types and more information about type casting).
Note that you should only supply the :switches
or the:strict
option.
If you supply both, an ArgumentError
exception will be raised.
Types
Switches parsed by OptionParser
may take zero or one arguments.
The following switches types take no arguments:
:boolean
- sets the value totrue
when given (see also the “Negation switches” section below):count
- counts the number of times the switch is given
The following switches take one argument:
:integer
- parses the value as an integer:float
- parses the value as a float:string
- parses the value as a string
If a switch can’t be parsed according to the given type, it is returned in the invalid options list.
Modifiers
Switches can be specified with modifiers, which change how they behave. The following modifiers are supported:
:keep
- keeps duplicated items instead of overriding them; works with all types except:count
. Specifyingswitch_name: :keep
assumes the type of:switch_name
will be:string
.
To use :keep
with a type other than :string
, use a list as the type
for the switch. For example: [foo: [:integer, :keep]]
.
Negation switches
In case a switch SWITCH
is specified to have type :boolean
, it may be
passed as --no-SWITCH
as well which will set the option to false
:
iex> OptionParser.parse(["--no-op", "path/to/file"], switches: [op: :boolean])
{[op: false], ["path/to/file"], []}
Parsing dynamic switches
OptionParser
also includes a dynamic mode where it will attempt to parse
switches dynamically. Such can be done by not specifying the :switches
or
:strict
option.
iex> OptionParser.parse(["--debug"])
{[debug: true], [], []}
Switches followed by a value will be assigned the value, as a string. Switches
without an argument, like --debug
in the examples above, will automatically be
set to true
.
Since Elixir converts switches to atoms, the dynamic mode will only parse
switches that translate to atoms used by the runtime. Therefore, the code below
likely won’t parse the given option since the :option_parser_example
atom is
never used anywhere:
OptionParser.parse(["--option-parser-example"])
# The :option_parser_example atom is not used anywhere below
However, the code below does since the :option_parser_example
atom is used
at some point later (or earlier) on:
{opts, _, _} = OptionParser.parse(["--option-parser-example"])
opts[:option_parser_example]
In other words, when using dynamic mode, Elixir will do the correct thing and
only parse options that are used by the runtime, ignoring all others. If you
would like to parse all switches, regardless if they exist or not, you can
force creation of atoms by passing allow_nonexistent_atoms: true
as option.
Such option is useful when you are building command-line applications that
receive dynamically-named arguments but must be used with care on long-running
systems.
Switches followed by a value will be assigned the value, as a string.
Switches without an argument, like --debug
in the examples above, will
automatically be set to true
.
Aliases
A set of aliases can be specified in the :aliases
option:
iex> OptionParser.parse(["-d"], aliases: [d: :debug])
{[debug: true], [], []}
Examples
Here are some examples of working with different types and modifiers:
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(["--verbose"], switches: [verbose: :count])
{[verbose: 1], [], []}
iex> OptionParser.parse(["-v", "-v"], aliases: [v: :verbose], strict: [verbose: :count])
{[verbose: 2], [], []}
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"], [], []}
The same as parse/2
but raises an OptionParser.ParseError
exception if any invalid options are given.
If there are no errors, returns a {parsed, rest}
tuple where:
parsed
is the list of parsed switches (same as inparse/2
)rest
is the list of arguments (same as inparse/2
)
Examples
iex> OptionParser.parse!(["--debug", "path/to/file"], strict: [debug: :boolean])
{[debug: true], ["path/to/file"]}
iex> OptionParser.parse!(["--limit", "xyz"], strict: [limit: :integer])
** (OptionParser.ParseError) 1 error found!
--limit : Expected type integer, got "xyz"
iex> OptionParser.parse!(["--unknown", "xyz"], strict: [])
** (OptionParser.ParseError) 1 error found!
--unknown : Unknown option
iex> OptionParser.parse!(["-l", "xyz", "-f", "bar"],
...> switches: [limit: :integer, foo: :integer], aliases: [l: :limit, f: :foo])
** (OptionParser.ParseError) 2 errors found!
-l : Expected type integer, got "xyz"
-f : Expected type integer, got "bar"
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"],
...> switches: [source: :string, verbose: :boolean])
{[source: "lib"], ["test/enum_test.exs", "--verbose"], []}
iex> OptionParser.parse_head(["--verbose", "--source", "lib", "test/enum_test.exs", "--unlock"],
...> switches: [source: :string, verbose: :boolean, unlock: :boolean])
{[verbose: true, source: "lib"], ["test/enum_test.exs", "--unlock"], []}
The same as parse_head/2
but raises an OptionParser.ParseError
exception if any invalid options are given.
If there are no errors, returns a {parsed, rest}
tuple where:
parsed
is the list of parsed switches (same as inparse_head/2
)rest
is the list of arguments (same as inparse_head/2
)
Examples
iex> OptionParser.parse_head!(["--source", "lib", "path/to/file", "--verbose"],
...> switches: [source: :string, verbose: :boolean])
{[source: "lib"], ["path/to/file", "--verbose"]}
iex> OptionParser.parse_head!(["--number", "lib", "test/enum_test.exs", "--verbose"],
...> strict: [number: :integer])
** (OptionParser.ParseError) 1 error found!
--number : Expected type integer, got "lib"
iex> OptionParser.parse_head!(["--verbose", "--source", "lib", "test/enum_test.exs", "--unlock"],
...> strict: [verbose: :integer, source: :integer])
** (OptionParser.ParseError) 2 errors found!
--verbose : Missing argument of type integer
--source : Expected type integer, got "lib"
Splits a string into argv/0
chunks.
This function splits the given string
into a list of strings in a similar
way to many shells.
Examples
iex> OptionParser.split("foo bar")
["foo", "bar"]
iex> OptionParser.split("foo \"bar baz\"")
["foo", "bar baz"]
to_argv(Enumerable.t(), options()) :: argv()
Receives a key-value enumerable and converts it to argv/0
.
Keys must be atoms. Keys with nil
value are discarded,
boolean values are converted to --key
or --no-key
(if the value is true
or false
, respectively),
and all other values are converted using Kernel.to_string/1
.
It is advised to pass to to_argv/2
the same set of options
given to parse/2
. Some switches can only be reconstructed
correctly with the switches
information in hand.
Examples
iex> OptionParser.to_argv([foo_bar: "baz"])
["--foo-bar", "baz"]
iex> OptionParser.to_argv([bool: true, bool: false, discarded: nil])
["--bool", "--no-bool"]
Some switches will output different values based on the switches flag:
iex> OptionParser.to_argv([number: 2], switches: [])
["--number", "2"]
iex> OptionParser.to_argv([number: 2], switches: [number: :count])
["--number", "--number"]