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https://github.com/clap-rs/clap
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113 lines
4 KiB
Markdown
113 lines
4 KiB
Markdown
# StructOpt [](https://travis-ci.org/TeXitoi/structopt) [](https://crates.io/crates/structopt) [](https://docs.rs/structopt-derive)
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Parse command line argument by defining a struct. It combines [clap](https://crates.io/crates/clap) with custom derive.
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**This README is in flux for v0.2 that's not yet published. Please refere to https://crates.io/crates/structopt to have a README syncronised with crates.io version.**
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## Documentation
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Find it on Docs.rs: [structopt-derive](https://docs.rs/structopt-derive) and [structopt](https://docs.rs/structopt).
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## Example
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Add `structopt` and `structopt-derive` to your dependencies of your `Cargo.toml`:
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```toml
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[dependencies]
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structopt = "0.2"
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```
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And then, in your rust file:
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```rust
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#[macro_use]
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extern crate structopt;
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use std::fs::PathBuf;
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use structopt::StructOpt;
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/// A basic example
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#[derive(StructOpt, Debug)]
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#[structopt(name = "basic")]
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struct Opt {
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// A flag, true if used in the command line. Note doc comment will
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// be used for the help message of the flag.
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/// Activate debug mode
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#[structopt(short = "d", long = "debug")]
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debug: bool,
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// The number of occurences of the `v/verbose` flag
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/// Verbose mode (-v, -vv, -vvv, etc.)
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#[structopt(short = "v", long = "verbose", parse(from_occurrences))]
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verbose: u8,
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/// Set speed
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#[structopt(short = "s", long = "speed", default_value = "42")]
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speed: f64,
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/// Output file
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#[structopt(short = "o", long = "output", parse(from_os_str))]
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output: PathBuf,
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/// Number of car
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#[structopt(short = "c", long = "car")]
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car: Option<i32>,
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/// admin_level to consider
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#[structopt(short = "l", long = "level")]
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level: Vec<String>,
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/// Files to process
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#[structopt(name = "FILE", parse(from_os_str))]
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files: Vec<PathBuf>,
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}
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fn main() {
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let opt = Opt::from_args();
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println!("{:?}", opt);
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}
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```
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Using this example:
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```
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$ ./basic
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error: The following required arguments were not provided:
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--output <output>
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USAGE:
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basic --output <output> --speed <speed>
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For more information try --help
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$ ./basic --help
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basic 0.1.8
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Guillaume Pinot <texitoi@texitoi.eu>
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A basic example
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USAGE:
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basic [FLAGS] [OPTIONS] --output <output> [--] [FILE]...
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FLAGS:
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-d, --debug Activate debug mode
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-h, --help Prints help information
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-V, --version Prints version information
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-v, --verbose Verbose mode
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OPTIONS:
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-c, --car <car> Number of car
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-l, --level <level>... admin_level to consider
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-o, --output <output> Output file
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-s, --speed <speed> Set speed [default: 42]
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ARGS:
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<FILE>... Files to process
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$ ./basic -o foo.txt
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Opt { debug: false, verbose: 0, speed: 42, output: "foo.txt", car: None, level: [], files: [] }
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$ ./basic -o foo.txt -dvvvs 1337 -l alice -l bob --car 4 bar.txt baz.txt
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Opt { debug: true, verbose: 3, speed: 1337, output: "foo.txt", car: Some(4), level: ["alice", "bob"], files: ["bar.txt", "baz.txt"] }
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```
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## Why
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I use [docopt](https://crates.io/crates/docopt) since a long time (pre rust 1.0). I really like the fact that you have a structure with the parsed argument: no need to convert `String` to `f64`, no useless `unwrap`. But on the other hand, I don't like to write by hand the usage string. That's like going back to the golden age of WYSIWYG editors. Field naming is also a bit artificial.
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Today, the new standard to read command line arguments in Rust is [clap](https://crates.io/crates/clap). This library is so feature full! But I think there is one downside: even if you can validate argument and expressing that an argument is required, you still need to transform something looking like a hashmap of string vectors to something useful for your application.
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Now, there is stable custom derive. Thus I can add to clap the automatic conversion that I miss. Here is the result.
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