The rust-argparse
is command-line parsing module for rust. It's inspired
by python's argparse
module.
Features:
- Supports standard (GNU) option conventions
- Properly typed values
- Automatically generated help and usage messages
Edit your Cargo.toml to add rust-argparse
to your project.
[dependencies]
argparse = "*"
The following code is a simple Rust program with command-line arguments:
extern crate argparse;
use argparse::{ArgumentParser, StoreTrue, Store};
fn main() {
let mut verbose = false;
let mut name = "World".to_string();
{ // this block limits scope of borrows by ap.refer() method
let mut ap = ArgumentParser::new();
ap.set_description("Greet somebody.");
ap.refer(&mut verbose)
.add_option(&["-v", "--verbose"], StoreTrue,
"Be verbose");
ap.refer(&mut name)
.add_option(&["--name"], Store,
"Name for the greeting");
ap.parse_args_or_exit();
}
if verbose {
println!("name is {}", name);
}
println!("Hello {}!", name);
}
Assuming the Rust code above is saved into a file greeting.rs
, let's see
what we have now:
$ rustc greeting.rs $ ./greeting -h Usage: ./greeting [OPTIONS] Greet somebody. optional arguments: -h, --help show this help message and exit -v, --verbose Be verbose --name NAME Name for the greeting $ ./greeting Hello World! $ ./greeting --name Bob Hello Bob! $ ./greeting -v --name Alice name is Alice Hello Alice!
The argument parser is created empty and is built incrementally. So we create a mutable variable:
extern crate argparse; use argparse::ArgumentParser; let mut parser = ArgumentParser::new();
There are optional customization methods. The most important one is:
parser.set_description("My command-line utility")
The descripion is rewrapped to fit 80 column string nicely. Just like option descriptions.
The refer
method creates a cell variable, which the result will be written
to:
let mut verbose = false; parser.refer(&mut verbose);
Next we add an options which control the variable: For example:
parser.refer(&mut verbose) .add_option(&["-v", "--verbose"], StoreTrue, "Be verbose");
You made add multiple options for the same variable:
parser.refer(&mut verbose) .add_option(&["-v", "--verbose"], StoreTrue, "Be verbose") .add_option(&["-q", "--quiet"], StoreFalse, "Be verbose");
Similarly positional arguments are added:
let mut command = String; parser.refer(&mut command) .add_argument("command", Store, "Command to run");
It's often useful to organize options into some kind of structure. You can easily borrow variables from the structure into option parser. For example:
struct Options { verbose: bool, } ... let mut options = Options { verbose: false } parser.refer(&mut options.verbose) .add_option(&["-v"], StoreTrue, "Be verbose");
All the complex work is done in parser.parse_args()
. But there is
a simpler option:
parser.parse_args_or_exit()
In case you don't want argparse to exit itself, you might use the
parse_args
function directly:
use std::process::exit; match parser.parse_args() { Ok(()) => {} Err(x) => { std::process::exit(x); } }
parser.refer<T>(var: &mut T) -> Ref
- Attach the variable to argument parser. The options are added to the
returned
Ref
object and modify a variable passed to the method. parser.add_option(names: &[&str], action: TypedAction, help: &str)
Add a single option which has no parameters. Most options must be added by
refer(..)
and methods onRef
object (see below).Example:
ap.add_option(&["-V", "--version"], Print(env!("CARGO_PKG_VERSION").to_string()), "Show version");
parser.set_description(descr: &str)
- Set description that is at the top of help message.
parser.stop_on_first_argument(val: bool)
- If called with
true
, parser will stop searching for options when first non-option (the one doesn't start with-
) argument is encountered. This is useful if you want to parse following options with another argparser or external program. parser.silence_double_dash(val: bool)
- If called with
true
(default), parser will not treat first double dash--
as positional argument. Usefalse
if you need to add some meaning to the--
marker. parser.print_usage(name: &str, writer: &mut Write)
- Prints usage string to stderr.
parser.print_help(name: &str, writer: &mut Write)
- Writes help to
writer
, used by--help
option internally. parser.parse_args()
- Method that does all the dirty work. And returns
Result
parser.parse_args_or_exit()
- Method that does all the dirty work. And in case of failure just
exit()
The argparse::Ref
object is returned from parser.refer()
.
The following methods are used to add and customize arguments:
option.add_option(names: &[&str], action: TypedAction, help: &str)
- Add an option. All items in names should be either in format
-X
or--long-option
(i.e. one dash and one char or two dashes and long name). How this option will be interpreted and whether it will have an argument dependes on the action. See below list of actions. option.add_argument(name: &str, action: TypedAction, help: &str)
- Add a positional argument
option.metavar(var: &str)
- A name of the argument in usage messages (for options having argument).
option.envvar(var: &str)
- A name of the environment variable to get option value from. The value
would be parsed with
FromStr::from_str
, just like an option havingStore
action. option.required()
- The option or argument is required (it's optional by default). If multiple options or multiple arguments are defined for this reference at least one of them is required.
The following actions are available out of the box. They may be used in either
add_option
or add_argument
:
Store
- An option has single argument. Stores a value from command-line in a
variable. Any type that has
FromStr
trait implemented may be used. StoreOption
As
Store
, but wrap value withSome
for use withOption
. For example:let mut x: Option<i32> = None; ap.refer(&mut x).add_option(&["-x"], StoreOption, "Set var x");
StoreConst(value)
- An option has no arguments. Store a hard-coded
value
into variable, when specified. Any type may be used. PushConst(value)
- An option has no arguments. Push a hard-coded
value
into variable, when specified. Any type may be used. Option might used for a list of operations to perform, whenrequired
is set for this variable, at least one operation is required. StoreTrue
- Stores boolean
true
value in a variable. (shortcut forStoreConst(true)
) StoreFalse
- Stores boolean
false
value in a variable. (shortcut forStoreConst(false)
) IncrBy(num)
- An option has no arguments. Increments the value stored in a variable by a
value
num
. Any type which hasAdd
trait may be used. DecrBy(nym)
- Decrements the value stored in a variable by a value
num
. Any type which hasAdd
trait may be used. Collect
- When used for an
--option
, requires single argument. When used for a positional argument consumes all remaining arguments. Parsed options are added to the list. I.e. aCollect
action requires aVec<int>
variable. Parses arguments usingFromStr
trait. List
When used for positional argument, works the same as
List
. When used as an option, consumes all remaining arguments.Note the usage of
List
is strongly discouraged, because of complex rules below. UseCollect
and positional options if possible. But usage ofList
action may be useful if you need shell expansion of anything other than last positional argument.Let's learn rules by example. For the next options:
ap.refer(&mut lst1).add_option(&["-X", "--xx"], List, "List1"); ap.refer(&mut lst2).add_argument("yy", List, "List2");
The following command line:
./run 1 2 3 -X 4 5 6
Will return
[1, 2, 3]
in thelst1
and the[4,5,6]
in thelst2
.Note that using when using
=
or equivalent short option mode, the 'consume all' mode is not enabled. I.e. in the following command-line:./run 1 2 -X3 4 --xx=5 6
The
lst1
has[3, 5]
andlst2
has[1, 2, 4, 6]
. The argument consuming also stops on--
or the next option:./run: -X 1 2 3 -- 4 5 6 ./run: -X 1 2 --xx=3 4 5 6
Both of the above parse
[4, 5, 6]
aslst1
and the[1, 2, 3]
as thelst2
.Print(value)
Print the text and exit (with status
0
). Useful for--version
option:ap.add_option(&["-V", "--version"], Print(env!("CARGO_PKG_VERSION").to_string()), "Show version");