Crate clap [−] [src]
Command Line Argument Parser for Rust
It is a simple to use, efficient, and full featured library for parsing command line arguments and subcommands when writing console, or terminal applications.
About
clap
is used to parse and validate the string of command line arguments provided by the
user at runtime. You provide the list of valid possibilities, and clap
handles the rest. This
means you focus on your applications functionality, and less on the parsing and validating of
arguments.
clap
also provides the traditional version and help switches (or flags) 'for free' meaning
automatically with no configuration. It does this by checking list of valid possibilities you
supplied and if you haven't them already (or only defined some of them), clap
will auto-
generate the applicable ones. If you are using subcommands, clap
will also auto-generate a
help
subcommand for you in addition to the traditional flags.
Once clap
parses the user provided string of arguments, it returns the matches along with any
applicable values. If the user made an error or typo, clap
informs them of the mistake and
exits gracefully. Because of this, you can make reasonable assumptions in your code about the
validity of the arguments.
Quick Examples
The following examples show a quick example of some of the very basic functionality of clap
.
For more advanced usage, such as requirements, exclusions, groups, multiple values and
occurrences see the video tutorials, documentation, or
examples/ directory of this crate's repository.
NOTE: All these examples are functionally the same, but show three different styles in
which to use clap
// (Full example with detailed comments in examples/01a_quick_example.rs) // // This example demonstrates clap's "usage strings" method of creating arguments which is less // less verbose extern crate clap; use clap::{Arg, App, SubCommand}; fn main() { let matches = App::new("myapp") .version("1.0") .author("Kevin K. <kbknapp@gmail.com>") .about("Does awesome things") .args_from_usage( "-c --config=[CONFIG] 'Sets a custom config file' <INPUT> 'Sets the input file to use' [debug]... -d 'Sets the level of debugging information'") .subcommand(SubCommand::with_name("test") .about("controls testing features") .version("1.3") .author("Someone E. <someone_else@other.com>") .arg_from_usage("-v --verbose 'Print test information verbosely'")) .get_matches(); // Calling .unwrap() is safe here because "INPUT" is required (if "INPUT" wasn't // required we could have used an 'if let' to conditionally get the value) println!("Using input file: {}", matches.value_of("INPUT").unwrap()); // Gets a value for config if supplied by user, or defaults to "default.conf" let config = matches.value_of("CONFIG").unwrap_or("default.conf"); println!("Value for config: {}", config); // Vary the output based on how many times the user used the "debug" flag // (i.e. 'myapp -d -d -d' or 'myapp -ddd' vs 'myapp -d' match matches.occurrences_of("debug") { 0 => println!("Debug mode is off"), 1 => println!("Debug mode is kind of on"), 2 => println!("Debug mode is on"), 3 | _ => println!("Don't be crazy"), } // You can information about subcommands by requesting their matches by name // (as below), requesting just the name used, or both at the same time if let Some(matches) = matches.subcommand_matches("test") { if matches.is_present("verbose") { println!("Printing verbosely..."); } else { println!("Printing normally..."); } } // more program logic goes here... }
The following example is functionally the same as the one above, but this method allows more advanced configuration options (not shown in this small example), or even dynamically generating arguments when desired. Both methods can be used together to get the best of both worlds (see the documentation, examples/, or video tutorials).
// (Full example with detailed comments in examples/01b_quick_example.rs) // // This example demonstrates clap's full 'builder pattern' style of creating arguments which is // more verbose, but allows easier editing, and at times more advanced options, or the possibility // to generate arguments dynamically. extern crate clap; use clap::{Arg, App, SubCommand}; fn main() { let matches = App::new("myapp") .version("1.0") .author("Kevin K. <kbknapp@gmail.com>") .about("Does awesome things") .arg(Arg::with_name("CONFIG") .short("c") .long("config") .help("Sets a custom config file") .takes_value(true)) .arg(Arg::with_name("INPUT") .help("Sets the input file to use") .required(true) .index(1)) .arg(Arg::with_name("debug") .short("d") .multiple(true) .help("Sets the level of debugging information")) .subcommand(SubCommand::with_name("test") .about("controls testing features") .version("1.3") .author("Someone E. <someone_else@other.com>") .arg(Arg::with_name("verbose") .short("v") .help("print test information verbosely"))) .get_matches(); // Calling .unwrap() is safe here because "INPUT" is required (if "INPUT" wasn't // required we could have used an 'if let' to conditionally get the value) println!("Using input file: {}", matches.value_of("INPUT").unwrap()); // Gets a value for config if supplied by user, or defaults to "default.conf" let config = matches.value_of("CONFIG").unwrap_or("default.conf"); println!("Value for config: {}", config); // Vary the output based on how many times the user used the "debug" flag // (i.e. 'myapp -d -d -d' or 'myapp -ddd' vs 'myapp -d' match matches.occurrences_of("debug") { 0 => println!("Debug mode is off"), 1 => println!("Debug mode is kind of on"), 2 => println!("Debug mode is on"), 3 | _ => println!("Don't be crazy"), } // You can information about subcommands by requesting their matches by name // (as below), requesting just the name used, or both at the same time if let Some(matches) = matches.subcommand_matches("test") { if matches.is_present("verbose") { println!("Printing verbosely..."); } else { println!("Printing normally..."); } } // more program logic goes here... }
The following combines the previous two examples by using the simplicity of the from_usage
methods and the performance of the Builder Pattern.
// (Full example with detailed comments in examples/01c_quick_example.rs) // // This example demonstrates clap's "usage strings" method of creating arguments which is less // less verbose #[macro_use] extern crate clap; fn main() { let matches = clap_app!(myapp => (version: "1.0") (author: "Kevin K. <kbknapp@gmail.com>") (about: "Does awesome things") (@arg CONFIG: -c --config +takes_value "Sets a custom config file") (@arg INPUT: +required "Sets the input file to use") (@arg debug: -d ... "Sets the level of debugging information") (@subcommand test => (about: "controls testing features") (version: "1.3") (author: "Someone E. <someone_else@other.com>") (@arg verbose: -v --verbose "Print test information verbosely") ) ).get_matches(); // Calling .unwrap() is safe here because "INPUT" is required (if "INPUT" wasn't // required we could have used an 'if let' to conditionally get the value) println!("Using input file: {}", matches.value_of("INPUT").unwrap()); // Gets a value for config if supplied by user, or defaults to "default.conf" let config = matches.value_of("CONFIG").unwrap_or("default.conf"); println!("Value for config: {}", config); // Vary the output based on how many times the user used the "debug" flag // (i.e. 'myapp -d -d -d' or 'myapp -ddd' vs 'myapp -d' match matches.occurrences_of("debug") { 0 => println!("Debug mode is off"), 1 => println!("Debug mode is kind of on"), 2 => println!("Debug mode is on"), 3 | _ => println!("Don't be crazy"), } // You can information about subcommands by requesting their matches by name // (as below), requesting just the name used, or both at the same time if let Some(matches) = matches.subcommand_matches("test") { if matches.is_present("verbose") { println!("Printing verbosely..."); } else { println!("Printing normally..."); } } // more program logic goes here... }
This final method shows how you can use a YAML file to build your CLI and keep your Rust source
tidy. First, create the cli.yml
file to hold your CLI options, but it could be called
anything we like (we'll use the same both examples above to keep it functionally equivilant):
name: myapp
version: 1.0
author: Kevin K. <kbknapp@gmail.com>
about: Does awesome things
args:
- CONFIG:
short: c
long: config
help: Sets a custom config file
takes_value: true
- INPUT:
help: Sets the input file to use
required: true
index: 1
- debug:
short: d
multiple: true
help: Sets the level of debugging information
subcommands:
- test:
about: controls testing features
version: 1.3
author: Someone E. <someone_else@other.com>
args:
- verbose:
short: v
help: print test information verbosely
Now we create our main.rs
file just like we would have with the previous two examples:
// (Full example with detailed comments in examples/17_yaml.rs) // // This example demonstrates clap's building from YAML style of creating arguments which is far // more clean, but takes a very small performance hit compared to the other two methods. #[macro_use] extern crate clap; use clap::App; fn main() { // The YAML file is found relative to the current file, similar to how modules are found let yaml = load_yaml!("cli.yml"); let matches = App::from_yaml(yaml).get_matches(); // Calling .unwrap() is safe here because "INPUT" is required (if "INPUT" wasn't // required we could have used an 'if let' to conditionally get the value) println!("Using input file: {}", matches.value_of("INPUT").unwrap()); // Gets a value for config if supplied by user, or defaults to "default.conf" let config = matches.value_of("CONFIG").unwrap_or("default.conf"); println!("Value for config: {}", config); // Vary the output based on how many times the user used the "debug" flag // (i.e. 'myapp -d -d -d' or 'myapp -ddd' vs 'myapp -d' match matches.occurrences_of("debug") { 0 => println!("Debug mode is off"), 1 => println!("Debug mode is kind of on"), 2 => println!("Debug mode is on"), 3 | _ => println!("Don't be crazy"), } // You can information about subcommands by requesting their matches by name // (as below), requesting just the name used, or both at the same time if let Some(matches) = matches.subcommand_matches("test") { if matches.is_present("verbose") { println!("Printing verbosely..."); } else { println!("Printing normally..."); } } // more program logic goes here... }
If you were to compile any of the above programs and run them with the flag --help
or -h
(or help
subcommand, since we defined test
as a subcommand) the following would be output
NOTE: The YAML option requires adding a special features
flag when compiling clap
because it is not compiled by default since it takes additional dependencies that some people
may not need. Simply change your clap = "1"
to clap = {version = "1", features = ["yaml"]}
in your Cargo.toml
to use the YAML version.
$ myapp --help
myapp 1.0
Kevin K. <kbknapp@gmail.com>
Does awesome things
USAGE:
MyApp [FLAGS] [OPTIONS] <INPUT> [SUBCOMMAND]
FLAGS:
-d Turn debugging information on
-h, --help Prints this message
-V, --version Prints version information
OPTIONS:
-c, --config <CONFIG> Sets a custom config file
ARGS:
INPUT The input file to use
SUBCOMMANDS:
help Prints this message
test Controls testing features
NOTE: You could also run myapp test --help
to see similar output and options for the
test
subcommand.
Try it!
Pre-Built Test
To try out the pre-built example, use the following steps:
- Clone the repo
$ git clone https://github.com/kbknapp/clap-rs && cd clap-rs/clap-tests
- Compile the example
$ cargo build --release
- Run the help info
$ ./target/release/claptests --help
- Play with the arguments!
BYOB (Build Your Own Binary)
To test out clap
's default auto-generated help/version follow these steps:
* Create a new cargo project $ cargo new fake --bin && cd fake
* Add clap
to your Cargo.toml
*
toml [dependencies] clap = "1"
- Add the following to your
src/main.rs
extern crate clap; use clap::App; fn main() { let _ = App::new("fake").version("v1.0-beta").get_matches(); }
- Build your program
$ cargo build --release
- Run w/ help or version
$ ./target/release/fake --help
or$ ./target/release/fake --version
Usage
For full usage, add clap
as a dependency in your Cargo.toml
file to use from crates.io:
[dependencies]
clap = "1"
Or track the latest on the master branch at github:
[dependencies.clap]
git = "https://github.com/kbknapp/clap-rs.git"
Add extern crate clap;
to your crate root.
Define a list of valid arguments for your program (see the documentation or examples/ directory of this repo)
Then run cargo build
or cargo update && cargo build
for your project.
Optional Dependencies / Features
If you'd like to keep your dependency list to only clap
, you can disable any features
that require an additional dependency. To do this, add this to your Cargo.toml
:
[dependencies.clap]
version = "1"
default-features = false
You can also selectively enable only the features you'd like to include, by adding:
[dependencies.clap]
version = "1"
default-features = false
# Cherry-pick the features you'd like to use
features = [ "suggestions", "color" ]
The following is a list of optional clap
features:
- "suggestions": Turns on the
Did you mean '--myoption' ?
feature for when users make typos. - "color": Turns on red error messages. This feature only works on non-Windows OSs.
- "lints": This is not included by default and should only be used while developing to run basic lints against changes. This can only be used on Rust nightly.
Dependencies Tree
The following graphic depicts clap
s dependency graph.
- Dashed Line: Optional dependency
- Red Color: NOT included by default (must use cargo
features
to enable)
More Information
You can find complete documentation on the github-pages site for this project.
You can also find usage examples in the examples/ directory of this repo.
Video Tutorials
There's also the video tutorial series Argument Parsing with Rust that I've been working on.
Note: Two new videos have just been added (08 From Usage, and
09 Typed Values), if you're already familiar with clap
but
want to know more about these two details you can check out those videos without watching the
previous few.
Note: Apologies for the resolution of the first video, it will be updated to a better resolution soon. The other videos have a proper resolution.
Running the tests
If contributing, you can run the tests as follows (assuming you're in the clap-rs
directory)
cargo test --features yaml && make -C clap-tests test
License
clap
is licensed under the MIT license. Please read the LICENSE-MIT
file in
this repository for more information.
Macros
arg_enum! |
Convenience macro to generate more complete enums with variants to be used as a type when
parsing arguments. This enum also provides a |
clap_app! |
App, Arg, SubCommand and Group builder macro (Usage-string like input) |
crate_version! |
Allows you pull the version for an from your Cargo.toml as MAJOR.MINOR.PATCH_PKGVERSION_PRE |
simple_enum! |
Convenience macro generated a simple enum with variants to be used as a type when parsing
arguments. This enum also provides a |
value_t! |
Convenience macro getting a typed value |
value_t_or_exit! |
Convenience macro getting a typed value |
Structs
App |
Used to create a representation of a command line program and all possible command line arguments. |
Arg |
The abstract representation of a command line argument used by the consumer of the library. Used to set all the options and relationships that define a valid argument for the program. |
ArgGroup |
|
ArgMatches |
Used to get information about the arguments that where supplied to the program at runtime by
the user. To get a new instance of this struct you use |
ClapError |
Command line argument parser error |
SubCommand |
The abstract representation of a command line subcommand used by the consumer of the library. |
Enums
AppSettings |
Application level settings, which affect how |
ClapErrorType |
Command line argument parser error types |
Format |