cliargs-rust

A library to parse command line arguments and print the help for Rust application.

This library provides the following functionalities:

• Supports POSIX & GNU like short and long options.
  • This library supports -- option.
  • This library doesn't support numeric short option.
  • This library supports not -ofoo but -o=foo as an alternative to -o foo for short option.
• Supports parsing with option configurations.
• Supports parsing with option configurations made from struct fields and attributes, and setting the option values to them.
• Supports parsing command line arguments including sub commands.
• Generates help text from option configurations.

Install

In Cargo.toml, write this crate as a dependency.

[dependencies]
cliargs = "0.5.1"

Usage

This crate provides the Cmd struct to parse command line arguments. The usage of this Cmd struct is as follows:

Creates a Cmd instance

The Cmd::new function creates a Cmd instance with original command line arguments. This function uses std::env::args_os and OsString#into_string to read command line arguments in order to avoid panic! call that the user cannot control.

use cliargs::Cmd;
use cliargs::errors::InvalidOsArg;

let cmd = match Cmd::new() {
    Ok(cmd) => cmd,
    Err(InvalidOsArg::OsArgsContainInvalidUnicode { index, os_arg }) => {
        panic!("Invalid Unicode data: {:?} (index: {})", os_arg, index);
    }
};

Creates a Cmd instance with the specified String array

The Cmd::with_strings function creates a Cmd instance with the specified String array.

use cliargs::Cmd;
use std::env;

let cmd = Cmd::with_strings(env::args());

Creates a Cmd instance with the specified OsString array

The Cmd::with_os_strings function creates a Cmd instance with the specified OsString array.

use cliargs::Cmd;
use cliargs::errors::InvalidOsArg;
use std::env;

let cmd = match Cmd::with_os_strings(env::args_os()) {
    Ok(cmd) => cmd,
    Err(InvalidOsArg::OsArgsContainInvalidUnicode { index, os_arg }) => {
        panic!("Invalid Unicode data: {:?} (index: {})", os_arg, index);
    }
};

Parses without configurations

The Cmd struct has the method which parses command line arguments without configurations. This method automatically divides command line arguments to command arguments, options, and option arguments.

Command line arguments starts with - or -- are options, and others are command arguments. If you want to specify a value to an option, follows "=" and the value after the option, like foo=123.

All command line arguments after -- are command arguments, even they starts with - or --.

use cliargs::Cmd;
use cliargs::errors::InvalidOption;

let mut cmd = Cmd::with_strings(vec![ /* ... */ ]);
match cmd.parse() {
    Ok(_) => { /* ... */ },
    Err(InvalidOption::OptionContainsInvalidChar { option }) => {
        panic!("Option contains invalid character: {option}");
    },
    Err(err) => panic!("Invalid option: {}", err.option()),
}

Parses with configurations

The Cmd struct has the method parse_with which parses command line arguments with configurations. This method takes an array of option configurations: OptCfg, and divides command line arguments to options and command arguments according to this configurations..

An option configuration has fields: store_key, names, has_arg, is_array, defaults, desc, arg_in_help, and validator.

store_key field is specified the key name to store the option value to the option map in the Cmd instance. If this field is not specified, the first element of names field is used instead.

names field is a string array and specified the option names, that are both long options and short options. The order of elements in this field is used in a help text. If you want to prioritize the output of short option name first in the help text, like -f, --foo-bar, but use the long option name as the key in the option map, write store_key and names fields as follows: OptCfg::with([store_key("foo-bar"), names(&["f", "foo-bar"])]).

has_arg field indicates the option requires one or more values. is_array field indicates the option can have multiple values. defaults field is an array of string which is used as default one or more option arguments if the option is not specified. desc is a description of the option for help text. arg_n_help field is a text which is output after option name and aliases as an option value in help text.

validator field is to set a function pointer which validates an option argument. This crate provides the validator cliargs::validators::validate_number<T> which validates whether an option argument is valid format as a number.

The ownership of the vector of option configurations which is passed as an argument of this method is moved to this method and set to the public field cfgs of Cmd instance. If you want to access the option configurations after parsing, get them from this field.

In addition,the help printing for an array of OptCfg is generated with Help.

use cliargs::{Cmd, OptCfg};
use cliargs::OptCfgParam::{names, has_arg, defaults, validator, desc, arg_in_help};
use cliargs::validators::validate_number;
use cliargs::errors::InvalidOption;

let mut cmd = Cmd::with_strings(vec![ /* ... */ ]);
let opt_cfgs = vec![
    OptCfg::with([
        names(&["foo-bar"]),
        desc("This is description of foo-bar."),
    ]),
    OptCfg::with([
        names(&["baz", "z"]),
        has_arg(true),
        defaults(&["1"]),
        desc("This is description of baz."),
        arg_in_help("<num>"),
        validator(validate_number::<u32>),
    ]),
];

match cmd.parse_with(opt_cfgs) {
    Ok(_) => { /* ... */ },
    Err(InvalidOption::OptionContainsInvalidChar { option }) => { /* ... */ },
    Err(InvalidOption::UnconfiguredOption { option }) => { /* ... */ },
    Err(InvalidOption::OptionNeedsArg { option, .. }) => { /* ... */ },
    Err(InvalidOption::OptionTakesNoArg { option, .. }) => { /* ... */ },
    Err(InvalidOption::OptionIsNotArray { option, .. }) => { /* ... */ },
    Err(InvalidOption::OptionArgIsInvalid { option, opt_arg, details, .. }) => { /* ... */ },
    Err(err) => panic!("Invalid option: {}", err.option()),
}

let opt_cfgs = cmd.opt_cfgs();

let mut help = Help::new();
help.add_text("This is the usage description.".to_string());
help.add_opts_with_margins(opt_cfgs, 2, 0);
help.print();

// (stdout)
// This is the usage description.
//   --foo-bar, -f    This is description of foo-bar.
//   --bar, -z <num>  This is description of baz.

Parse for a OptStore struct

The Cmd struct has the method parse_for which parses command line arguments and set their option values to the option store which is passed as an argument.

This method divides command line arguments to command arguments and options, then sets each option value to a curresponding field of the option store.

Within this method, a vector of OptCfg is made from the fields of the option store. This OptCfg vector is set to the public field cfgs of the Cmd instance. If you want to access this option configurations, get them from this field.

An option configuration corresponding to each field of an option store is determined by its type and opt field attribute. If the type is bool, the option takes no argument. If the type is integer, floating point number or string, the option can takes single option argument, therefore it can appear once in command line arguments. If the type is a vector, the option can takes multiple option arguments, therefore it can appear multiple times in command line arguments.

A opt field attribute can have the following pairs of name and value: one is cfg to specify names and defaults fields of OptCfg struct, another is desc to specify desc field, and yet another is arg to specify arg_in_help field.

The format of cfg is like cfg="f,foo=123". The left side of the equal sign is the option name(s), and the right side is the default value(s). If there is no equal sign, it is determined that only the option name is specified. If you want to specify multiple option names, separate them with commas. If you want to specify multiple default values, separate them with commas and round them with square brackets, like [1,2,3]. If you want to use your favorite carachter as a separator, you can use it by putting it on the left side of the open square bracket, like /[1/2/3].

NOTE: A default value of empty string array option in a field attribute is [], like #[opt(cfg="=[]")], but it doesn't represent an array which contains only one empty string. If you want to specify an array which contains only one emtpy string, write nothing after = symbol, like #[opt(cfg="=")].

use cliargs::Cmd;
use cliargs::errors::InvalidOption;

#[derive(cliargs::OptStore)]
struct MyOptions {
    #[opt(cfg = "f,foo-bar", desc="The description of foo_bar.")]
    foo_bar: bool,
    #[opt(cfg = "b,baz", desc="The description of baz.", arg="<s>")]
    baz: String,
}
let mut my_options = MyOptions::with_defaults();

let mut cmd = Cmd::with_strings(vec![ /* ... */ ]);
match cmd.parse_for(&mut my_options) {
    Ok(_) => { /* ... */ },
    Err(InvalidOption::OptionContainsInvalidChar { option }) => { /* ... */ },
    Err(InvalidOption::UnconfiguredOption { option }) => { /* ... */ },
    Err(InvalidOption::OptionNeedsArg { option, .. }) => { /* ... */ },
    Err(InvalidOption::OptionTakesNoArg { option, .. }) => { /* ... */ },
    Err(InvalidOption::OptionIsNotArray { option, .. }) => { /* ... */ },
    Err(InvalidOption::OptionArgIsInvalid { option, opt_arg, details, .. }) => { /* ... */ },
    Err(err) => panic!("Invalid option: {}", err.option()),
}

let opt_cfgs = cmd.opt_cfgs();

let mut help = Help::new();
help.add_text("This is the usage description.".to_string());
help.add_opts_with_margins(opt_cfgs, 2, 0);
help.print();

// (stdout)
// This is the usage description.
//   -f, --foo-bar  This is description of foo_bar.
//   -z, --baz <s>  This is description of baz.

Supports parsing command line arguments including sub commands

This crate provides methods Cmd#parse_until_sub_cmd, Cmd#parse_until_sub_cmd_with, and Cmd#parse_until_sub_cmd_for for parsing command line arguments including sub commands.

These methods correspond to Cmd#parse, Cmd#parse_with, and Cmd#parse_for, respectively, and behave the same except that they stop parsing before the first command argument (= sub command) and return a Cmd instance containing the arguments starting from the the sub command.

The folowing is an example code using Cmd#parse_until_sub_cmd:

use cliargs::Cmd;
use cliargs::errors::InvalidOption;

let mut cmd = Cmd::with_strings([ /* ... */ ]);

match cmd.parse_until_sub_cmd() {
    Ok(Some(mut sub_cmd)) => {
        let sub_cmd_name = sub_cmd.name();
        match sub_cmd.parse() {
            Ok(_) => { /* ... */ },
            Err(err) => panic!("Invalid option: {}", err.option()),
        }
    },
    Ok(None) => { /* ... */ },
    Err(InvalidOption::OptionContainsInvalidChar { option }) => {
        panic!("Option contains invalid character: {option}");
    },
    Err(err) => panic!("Invalid option: {}", err.option()),
}

Supporting Rust versions

This crate supports Rust 1.74.1 or later.

% cargo msrv --no-check-feedback
Fetching index
Determining the Minimum Supported Rust Version (MSRV) for toolchain x86_64-apple-darwin
Using check command cargo check
   Finished The MSRV is: 1.74.1   ████████████████████████████████████████████ 00:00:04

License

Copyright (C) 2024 Takayuki Sato

This program is free software under MIT License.
See the file LICENSE in this distribution for more details.