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README.md
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README.md
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# clap-rs
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Command Line Argument Parser written in Rust
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A simply library for parsing command line arguments when writing
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command line and console applications.
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You can use `clap` to lay out a list of possible valid command line arguments and let `clap` parse the string given by the user at runtime.
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When using `clap` you define a set of parameters and rules for your arguments and at runtime `clap` will determine their validity.
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Also, `clap` provides the traditional version and help switches 'for free' by parsing the list of possible valid arguments lazily at runtime.
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i.e. only when it's been determined that the user wants or needs to see the help and version information.
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After defining a list of possible valid arguments you get a list of matches that the user supplied at runtime. You can then use this list to
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determine the functioning of your program.
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Example:
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```rust
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extern crate clap;
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use clap::{Arg, App};
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// ...
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let matches = App::new("MyApp")
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.version("1.0")
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.author("Kevin K. <kbknapp@gmail.com>")
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.about("Does awesome things")
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.arg(Arg::new("config")
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.short("c")
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.long("config")
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.help("Sets a custom config file")
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.takes_value(true))
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.arg(Arg::new("output")
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.help("Sets an optional output file")
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.index(1))
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.arg(Arg::new("debug")
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.short("d")
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.multiple(true)
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.help("Turn debugging information on"))
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.get_matches();
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if let Some(o) = matches.value_of("output") {
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println!("Value for output: {}", o);
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}
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if let Some(c) = matches.value_of("config") {
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println!("Value for config: {}", c);
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}
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match matches.occurrences_of("debug") {
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0 => println!("Debug mode is off"),
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1 => println!("Debug mode is kind of on"),
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2 => println!("Debug mode is on"),
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3 | _ => println!("Don't be crazy"),
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}
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// more porgram logic goes here...
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```
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If you were to compile the above program and run it with the flag `--help` or `-h` the following output woud be presented
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```sh
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$ myprog --help
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MyApp 1.0
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Kevin K. <kbknapp@gmail.com>
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Does awesome things
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USAGE:
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MyApp [FLAGS] [OPTIONS] [POSITIONAL]
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FLAGS:
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-d Turn debugging information on
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-h,--help Prints this message
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-v,--version Prints version information
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OPTIONS:
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-c,--config <config> Sets a custom config file
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POSITIONAL ARGUMENTS:
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output Sets an optional output file
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```
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