Struct clap::Command

pub struct Command { /* private fields */ }

Build a command-line interface.

This includes defining arguments, subcommands, parser behavior, and help output. Once all configuration is complete, the Command::get_matches family of methods starts the runtime-parsing process. These methods then return information about the user supplied arguments (or lack thereof).

When deriving a Parser, you can use CommandFactory::command to access the Command.

• Basic API
• Application-wide Settings
• Command-specific Settings
• Subcommand-specific Settings
• Reflection

Examples

let m = Command::new("My Program")
    .author("Me, me@mail.com")
    .version("1.0.2")
    .about("Explains in brief what the program does")
    .arg(
        Arg::new("in_file")
    )
    .after_help("Longer explanation to appear after the options when \
                 displaying the help information from --help or -h")
    .get_matches();

// Your program logic starts here...

Implementations

impl Command

Basic API

pub fn new(name: impl Into<Str>) -> Command

Creates a new instance of an Command.

It is common, but not required, to use binary name as the name. This name will only be displayed to the user when they request to print version or help and usage information.

See also command! and crate_name!.

Examples

Command::new("My Program")

pub fn arg(self, a: impl Into<Arg>) -> Command

Adds an argument to the list of valid possibilities.

Examples

Command::new("myprog")
    // Adding a single "flag" argument with a short and help text, using Arg::new()
    .arg(
        Arg::new("debug")
           .short('d')
           .help("turns on debugging mode")
    )
    // Adding a single "option" argument with a short, a long, and help text using the less
    // verbose Arg::from()
    .arg(
        arg!(-c --config <CONFIG> "Optionally sets a config file to use")
    )

pub fn args(self, args: impl IntoIterator<Item = impl Into<Arg>>) -> Command

Adds multiple arguments to the list of valid possibilities.

Examples

Command::new("myprog")
    .args([
        arg!(-d --debug "turns on debugging info"),
        Arg::new("input").help("the input file to use")
    ])

pub fn mut_arg<F>(self, arg_id: impl AsRef<str>, f: F) -> Commandwhere F: FnOnce(Arg) -> Arg,

Allows one to mutate an Arg after it’s been added to a Command.

Panics

If the argument is undefined

Examples

let mut cmd = Command::new("foo")
    .arg(Arg::new("bar")
        .short('b')
        .action(ArgAction::SetTrue))
    .mut_arg("bar", |a| a.short('B'));

let res = cmd.try_get_matches_from_mut(vec!["foo", "-b"]);

// Since we changed `bar`'s short to "B" this should err as there
// is no `-b` anymore, only `-B`

assert!(res.is_err());

let res = cmd.try_get_matches_from_mut(vec!["foo", "-B"]);
assert!(res.is_ok());

pub fn mut_args<F>(self, f: F) -> Commandwhere F: FnMut(Arg) -> Arg,

Allows one to mutate all Args after they’ve been added to a Command.

This does not affect the built-in --help or --version arguments.

Examples

let mut cmd = Command::new("foo")
    .arg(Arg::new("bar")
        .long("bar")
        .action(ArgAction::SetTrue))
    .arg(Arg::new("baz")
        .long("baz")
        .action(ArgAction::SetTrue))
    .mut_args(|a| {
        if let Some(l) = a.get_long().map(|l| format!("prefix-{l}")) {
            a.long(l)
        } else {
            a
        }
    });

let res = cmd.try_get_matches_from_mut(vec!["foo", "--bar"]);

// Since we changed `bar`'s long to "prefix-bar" this should err as there
// is no `--bar` anymore, only `--prefix-bar`.

assert!(res.is_err());

let res = cmd.try_get_matches_from_mut(vec!["foo", "--prefix-bar"]);
assert!(res.is_ok());

pub fn mut_subcommand<F>(self, name: impl AsRef<str>, f: F) -> Commandwhere F: FnOnce(Command) -> Command,

Allows one to mutate a Command after it’s been added as a subcommand.

This can be useful for modifying auto-generated arguments of nested subcommands with Command::mut_arg.

Panics

If the subcommand is undefined

Examples

let mut cmd = Command::new("foo")
        .subcommand(Command::new("bar"))
        .mut_subcommand("bar", |subcmd| subcmd.disable_help_flag(true));

let res = cmd.try_get_matches_from_mut(vec!["foo", "bar", "--help"]);

// Since we disabled the help flag on the "bar" subcommand, this should err.

assert!(res.is_err());

let res = cmd.try_get_matches_from_mut(vec!["foo", "bar"]);
assert!(res.is_ok());

pub fn group(self, group: impl Into<ArgGroup>) -> Command

Adds an ArgGroup to the application.

ArgGroups are a family of related arguments. By placing them in a logical group, you can build easier requirement and exclusion rules.

Example use cases:

• Make an entire ArgGroup required, meaning that one (and only one) argument from that group must be present at runtime.
• Name an ArgGroup as a conflict to another argument. Meaning any of the arguments that belong to that group will cause a failure if present with the conflicting argument.
• Ensure exclusion between arguments.
• Extract a value from a group instead of determining exactly which argument was used.

Examples

The following example demonstrates using an ArgGroup to ensure that one, and only one, of the arguments from the specified group is present at runtime.

Command::new("cmd")
    .arg(arg!(--"set-ver" <ver> "set the version manually").required(false))
    .arg(arg!(--major "auto increase major"))
    .arg(arg!(--minor "auto increase minor"))
    .arg(arg!(--patch "auto increase patch"))
    .group(ArgGroup::new("vers")
         .args(["set-ver", "major", "minor","patch"])
         .required(true))

pub fn groups( self, groups: impl IntoIterator<Item = impl Into<ArgGroup>> ) -> Command

Adds multiple ArgGroups to the Command at once.

Examples

Command::new("cmd")
    .arg(arg!(--"set-ver" <ver> "set the version manually").required(false))
    .arg(arg!(--major         "auto increase major"))
    .arg(arg!(--minor         "auto increase minor"))
    .arg(arg!(--patch         "auto increase patch"))
    .arg(arg!(-c <FILE>       "a config file").required(false))
    .arg(arg!(-i <IFACE>      "an interface").required(false))
    .groups([
        ArgGroup::new("vers")
            .args(["set-ver", "major", "minor","patch"])
            .required(true),
        ArgGroup::new("input")
            .args(["c", "i"])
    ])

pub fn subcommand(self, subcmd: impl Into<Command>) -> Command

Adds a subcommand to the list of valid possibilities.

Subcommands are effectively sub-Commands, because they can contain their own arguments, subcommands, version, usage, etc. They also function just like Commands, in that they get their own auto generated help, version, and usage.

A subcommand’s Command::name will be used for:

• The argument the user passes in
• Programmatically looking up the subcommand

Examples

Command::new("myprog")
    .subcommand(Command::new("config")
        .about("Controls configuration features")
        .arg(arg!(<config> "Required configuration file to use")))

pub fn subcommands( self, subcmds: impl IntoIterator<Item = impl Into<Command>> ) -> Command

Adds multiple subcommands to the list of valid possibilities.

Examples

.subcommands( [
       Command::new("config").about("Controls configuration functionality")
                                .arg(Arg::new("config_file")),
       Command::new("debug").about("Controls debug functionality")])

pub fn defer(self, deferred: fn(_: Command) -> Command) -> Command

Delay initialization for parts of the Command

This is useful for large applications to delay definitions of subcommands until they are being invoked.

Examples

Command::new("myprog")
    .subcommand(Command::new("config")
        .about("Controls configuration features")
        .defer(|cmd| {
            cmd.arg(arg!(<config> "Required configuration file to use"))
        })
    )

pub fn debug_assert(self)

Catch problems earlier in the development cycle.

Most error states are handled as asserts under the assumption they are programming mistake and not something to handle at runtime. Rather than relying on tests (manual or automated) that exhaustively test your CLI to ensure the asserts are evaluated, this will run those asserts in a way convenient for running as a test.

Note:: This will not help with asserts in ArgMatches, those will need exhaustive testing of your CLI.

Examples

fn cmd() -> Command {
    Command::new("foo")
        .arg(
            Arg::new("bar").short('b').action(ArgAction::SetTrue)
        )
}

#[test]
fn verify_app() {
    cmd().debug_assert();
}

fn main() {
    let m = cmd().get_matches_from(vec!["foo", "-b"]);
    println!("{}", m.get_flag("bar"));
}

pub fn error( &mut self, kind: ErrorKind, message: impl Display ) -> Error<RichFormatter>

Custom error message for post-parsing validation

Examples

let mut cmd = Command::new("myprog");
let err = cmd.error(ErrorKind::InvalidValue, "Some failure case");

pub fn get_matches(self) -> ArgMatches

Parse env::args_os, exiting on failure.

Panics

If contradictory arguments or settings exist.

Examples

let matches = Command::new("myprog")
    // Args and options go here...
    .get_matches();

pub fn get_matches_mut(&mut self) -> ArgMatches

Parse env::args_os, exiting on failure.

Like Command::get_matches but doesn’t consume the Command.

Panics

If contradictory arguments or settings exist.

Examples

let mut cmd = Command::new("myprog")
    // Args and options go here...
    ;
let matches = cmd.get_matches_mut();

pub fn try_get_matches(self) -> Result<ArgMatches, Error<RichFormatter>>

Parse env::args_os, returning a clap::Result on failure.

NOTE: This method WILL NOT exit when --help or --version (or short versions) are used. It will return a clap::Error, where the kind is a ErrorKind::DisplayHelp or ErrorKind::DisplayVersion respectively. You must call Error::exit or perform a std::process::exit.

Panics

If contradictory arguments or settings exist.

Examples

let matches = Command::new("myprog")
    // Args and options go here...
    .try_get_matches()
    .unwrap_or_else(|e| e.exit());

pub fn get_matches_from<I, T>(self, itr: I) -> ArgMatcheswhere I: IntoIterator<Item = T>, T: Into<OsString> + Clone,

Parse the specified arguments, exiting on failure.

NOTE: The first argument will be parsed as the binary name unless Command::no_binary_name is used.

Panics

If contradictory arguments or settings exist.

Examples

let arg_vec = vec!["my_prog", "some", "args", "to", "parse"];

let matches = Command::new("myprog")
    // Args and options go here...
    .get_matches_from(arg_vec);

pub fn try_get_matches_from<I, T>( self, itr: I ) -> Result<ArgMatches, Error<RichFormatter>>where I: IntoIterator<Item = T>, T: Into<OsString> + Clone,

Parse the specified arguments, returning a clap::Result on failure.

NOTE: This method WILL NOT exit when --help or --version (or short versions) are used. It will return a clap::Error, where the kind is a ErrorKind::DisplayHelp or ErrorKind::DisplayVersion respectively. You must call Error::exit or perform a std::process::exit yourself.

NOTE: The first argument will be parsed as the binary name unless Command::no_binary_name is used.

Panics

If contradictory arguments or settings exist.

Examples

let arg_vec = vec!["my_prog", "some", "args", "to", "parse"];

let matches = Command::new("myprog")
    // Args and options go here...
    .try_get_matches_from(arg_vec)
    .unwrap_or_else(|e| e.exit());

pub fn try_get_matches_from_mut<I, T>( &mut self, itr: I ) -> Result<ArgMatches, Error<RichFormatter>>where I: IntoIterator<Item = T>, T: Into<OsString> + Clone,

Parse the specified arguments, returning a clap::Result on failure.

Like Command::try_get_matches_from but doesn’t consume the Command.

NOTE: This method WILL NOT exit when --help or --version (or short versions) are used. It will return a clap::Error, where the kind is a ErrorKind::DisplayHelp or ErrorKind::DisplayVersion respectively. You must call Error::exit or perform a std::process::exit yourself.

NOTE: The first argument will be parsed as the binary name unless Command::no_binary_name is used.

Panics

If contradictory arguments or settings exist.

Examples

let arg_vec = vec!["my_prog", "some", "args", "to", "parse"];

let mut cmd = Command::new("myprog");
    // Args and options go here...
let matches = cmd.try_get_matches_from_mut(arg_vec)
    .unwrap_or_else(|e| e.exit());

pub fn print_help(&mut self) -> Result<(), Error>

Prints the short help message (-h) to io::stdout().

See also Command::print_long_help.

Examples

let mut cmd = Command::new("myprog");
cmd.print_help();

pub fn print_long_help(&mut self) -> Result<(), Error>

Prints the long help message (--help) to io::stdout().

See also Command::print_help.

Examples

let mut cmd = Command::new("myprog");
cmd.print_long_help();

pub fn render_help(&mut self) -> StyledStr

Render the short help message (-h) to a StyledStr

See also Command::render_long_help.

Examples

use std::io;
let mut cmd = Command::new("myprog");
let mut out = io::stdout();
let help = cmd.render_help();
println!("{help}");

pub fn render_long_help(&mut self) -> StyledStr

Render the long help message (--help) to a StyledStr.

See also Command::render_help.

Examples

use std::io;
let mut cmd = Command::new("myprog");
let mut out = io::stdout();
let help = cmd.render_long_help();
println!("{help}");

pub fn render_version(&self) -> String

Version message rendered as if the user ran -V.

See also Command::render_long_version.

Coloring

This function does not try to color the message nor it inserts any ANSI escape codes.

Examples

use std::io;
let cmd = Command::new("myprog");
println!("{}", cmd.render_version());

pub fn render_long_version(&self) -> String

Version message rendered as if the user ran --version.

See also Command::render_version.

Coloring

This function does not try to color the message nor it inserts any ANSI escape codes.

Examples

use std::io;
let cmd = Command::new("myprog");
println!("{}", cmd.render_long_version());

pub fn render_usage(&mut self) -> StyledStr

Usage statement

Examples

use std::io;
let mut cmd = Command::new("myprog");
println!("{}", cmd.render_usage());

impl Command

Application-wide Settings

These settings will apply to the top-level command and all subcommands, by default. Some settings can be overridden in subcommands.

pub fn no_binary_name(self, yes: bool) -> Command

Specifies that the parser should not assume the first argument passed is the binary name.

This is normally the case when using a “daemon” style mode. For shells / REPLs, see Command::multicall.

Examples

let m = Command::new("myprog")
    .no_binary_name(true)
    .arg(arg!(<cmd> ... "commands to run"))
    .get_matches_from(vec!["command", "set"]);

let cmds: Vec<_> = m.get_many::<String>("cmd").unwrap().collect();
assert_eq!(cmds, ["command", "set"]);

pub fn ignore_errors(self, yes: bool) -> Command

Try not to fail on parse errors, like missing option values.

NOTE: This choice is propagated to all child subcommands.

Examples

let cmd = Command::new("cmd")
  .ignore_errors(true)
  .arg(arg!(-c --config <FILE> "Sets a custom config file"))
  .arg(arg!(-x --stuff <FILE> "Sets a custom stuff file"))
  .arg(arg!(f: -f "Flag"));

let r = cmd.try_get_matches_from(vec!["cmd", "-c", "file", "-f", "-x"]);

assert!(r.is_ok(), "unexpected error: {r:?}");
let m = r.unwrap();
assert_eq!(m.get_one::<String>("config").unwrap(), "file");
assert!(m.get_flag("f"));
assert_eq!(m.get_one::<String>("stuff"), None);

pub fn args_override_self(self, yes: bool) -> Command

Replace prior occurrences of arguments rather than error

For any argument that would conflict with itself by default (e.g. ArgAction::Set, it will now override itself.

This is the equivalent to saying the foo arg using Arg::overrides_with("foo") for all defined arguments.

NOTE: This choice is propagated to all child subcommands.

pub fn dont_delimit_trailing_values(self, yes: bool) -> Command

Disables the automatic delimiting of values after -- or when Command::trailing_var_arg was used.

NOTE: The same thing can be done manually by setting the final positional argument to Arg::value_delimiter(None). Using this setting is safer, because it’s easier to locate when making changes.

NOTE: This choice is propagated to all child subcommands.

Examples

Command::new("myprog")
    .dont_delimit_trailing_values(true)
    .get_matches();

pub fn color(self, color: ColorChoice) -> Command

Available on crate feature color only.

Sets when to color output.

NOTE: This choice is propagated to all child subcommands.

NOTE: Default behaviour is ColorChoice::Auto.

Examples

Command::new("myprog")
    .color(ColorChoice::Never)
    .get_matches();

pub fn styles(self, styles: Styles) -> Command

Available on crate features color and unstable-styles only.

Sets the Styles for terminal output

NOTE: This choice is propagated to all child subcommands.

NOTE: Default behaviour is Styles::default.

Examples

let styles = styling::Styles::styled()
    .header(styling::AnsiColor::Green.on_default() | styling::Effects::BOLD)
    .usage(styling::AnsiColor::Green.on_default() | styling::Effects::BOLD)
    .literal(styling::AnsiColor::Blue.on_default() | styling::Effects::BOLD)
    .placeholder(styling::AnsiColor::Cyan.on_default());
Command::new("myprog")
    .styles(styles)
    .get_matches();

pub fn term_width(self, width: usize) -> Command

Available on non-crate feature unstable-v5 or crate feature wrap_help only.

Sets the terminal width at which to wrap help messages.

Using 0 will ignore terminal widths and use source formatting.

Defaults to current terminal width when wrap_help feature flag is enabled. If current width cannot be determined, the default is 100.

unstable-v5 feature: Defaults to unbound, being subject to Command::max_term_width.

NOTE: This setting applies globally and not on a per-command basis.

NOTE: This requires the wrap_help feature

Examples

Command::new("myprog")
    .term_width(80)

pub fn max_term_width(self, width: usize) -> Command

Available on non-crate feature unstable-v5 or crate feature wrap_help only.

Limit the line length for wrapping help when using the current terminal’s width.

This only applies when term_width is unset so that the current terminal’s width will be used. See Command::term_width for more details.

Using 0 will ignore this, always respecting Command::term_width (default).

unstable-v5 feature: Defaults to 100.

NOTE: This setting applies globally and not on a per-command basis.

NOTE: This requires the wrap_help feature

Examples

Command::new("myprog")
    .max_term_width(100)

pub fn disable_version_flag(self, yes: bool) -> Command

Disables -V and --version flag.

Examples

let res = Command::new("myprog")
    .disable_version_flag(true)
    .try_get_matches_from(vec![
        "myprog", "-V"
    ]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind(), ErrorKind::UnknownArgument);

pub fn propagate_version(self, yes: bool) -> Command

Specifies to use the version of the current command for all subcommands.

Defaults to false; subcommands have independent version strings from their parents.

NOTE: This choice is propagated to all child subcommands.

Examples

Command::new("myprog")
    .version("v1.1")
    .propagate_version(true)
    .subcommand(Command::new("test"))
    .get_matches();
// running `$ myprog test --version` will display
// "myprog-test v1.1"

pub fn next_line_help(self, yes: bool) -> Command

Places the help string for all arguments and subcommands on the line after them.

NOTE: This choice is propagated to all child subcommands.

Examples

Command::new("myprog")
    .next_line_help(true)
    .get_matches();

pub fn disable_help_flag(self, yes: bool) -> Command

Disables -h and --help flag.

NOTE: This choice is propagated to all child subcommands.

Examples

let res = Command::new("myprog")
    .disable_help_flag(true)
    .try_get_matches_from(vec![
        "myprog", "-h"
    ]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind(), ErrorKind::UnknownArgument);

pub fn disable_help_subcommand(self, yes: bool) -> Command

Disables the help subcommand.

NOTE: This choice is propagated to all child subcommands.

Examples

let res = Command::new("myprog")
    .disable_help_subcommand(true)
    // Normally, creating a subcommand causes a `help` subcommand to automatically
    // be generated as well
    .subcommand(Command::new("test"))
    .try_get_matches_from(vec![
        "myprog", "help"
    ]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind(), ErrorKind::InvalidSubcommand);

pub fn disable_colored_help(self, yes: bool) -> Command

Disables colorized help messages.

NOTE: This choice is propagated to all child subcommands.

Examples

Command::new("myprog")
    .disable_colored_help(true)
    .get_matches();

pub fn help_expected(self, yes: bool) -> Command

Panic if help descriptions are omitted.

NOTE: When deriving Parser, you could instead check this at compile-time with #![deny(missing_docs)]

NOTE: This choice is propagated to all child subcommands.

Examples

Command::new("myprog")
    .help_expected(true)
    .arg(
        Arg::new("foo").help("It does foo stuff")
        // As required via `help_expected`, a help message was supplied
     )

Panics

Command::new("myapp")
    .help_expected(true)
    .arg(
        Arg::new("foo")
        // Someone forgot to put .about("...") here
        // Since the setting `help_expected` is activated, this will lead to
        // a panic (if you are in debug mode)
    )

pub fn hide_possible_values(self, yes: bool) -> Command

Tells clap not to print possible values when displaying help information.

This can be useful if there are many values, or they are explained elsewhere.

To set this per argument, see Arg::hide_possible_values.

NOTE: This choice is propagated to all child subcommands.

pub fn infer_long_args(self, yes: bool) -> Command

Allow partial matches of long arguments or their aliases.

For example, to match an argument named --test, one could use --t, --te, --tes, and --test.

NOTE: The match must not be ambiguous at all in order to succeed. i.e. to match --te to --test there could not also be another argument or alias --temp because both start with --te

NOTE: This choice is propagated to all child subcommands.

pub fn infer_subcommands(self, yes: bool) -> Command

Allow partial matches of subcommand names and their aliases.

For example, to match a subcommand named test, one could use t, te, tes, and test.

NOTE: The match must not be ambiguous at all in order to succeed. i.e. to match te to test there could not also be a subcommand or alias temp because both start with te

CAUTION: This setting can interfere with positional/free arguments, take care when designing CLIs which allow inferred subcommands and have potential positional/free arguments whose values could start with the same characters as subcommands. If this is the case, it’s recommended to use settings such as Command::args_conflicts_with_subcommands in conjunction with this setting.

NOTE: This choice is propagated to all child subcommands.

Examples

let m = Command::new("prog")
    .infer_subcommands(true)
    .subcommand(Command::new("test"))
    .get_matches_from(vec![
        "prog", "te"
    ]);
assert_eq!(m.subcommand_name(), Some("test"));

impl Command

Command-specific Settings

These apply only to the current command and are not inherited by subcommands.

pub fn name(self, name: impl Into<Str>) -> Command

(Re)Sets the program’s name.

See Command::new for more details.

Examples

let cmd = clap::command!()
    .name("foo");

// continued logic goes here, such as `cmd.get_matches()` etc.

pub fn bin_name(self, name: impl IntoResettable<String>) -> Command

Overrides the runtime-determined name of the binary for help and error messages.

This should only be used when absolutely necessary, such as when the binary name for your application is misleading, or perhaps not how the user should invoke your program.

Pro-tip: When building things such as third party cargo subcommands, this setting should be used!

NOTE: This does not change or set the name of the binary file on disk. It only changes what clap thinks the name is for the purposes of error or help messages.

Examples

Command::new("My Program")
     .bin_name("my_binary")

pub fn display_name(self, name: impl IntoResettable<String>) -> Command

Overrides the runtime-determined display name of the program for help and error messages.

Examples

Command::new("My Program")
     .display_name("my_program")

pub fn author(self, author: impl IntoResettable<Str>) -> Command

Sets the author(s) for the help message.

Pro-tip: Use claps convenience macro crate_authors! to automatically set your application’s author(s) to the same thing as your crate at compile time.

NOTE: A custom help_template is needed for author to show up.

Examples

Command::new("myprog")
     .author("Me, me@mymain.com")

pub fn about(self, about: impl IntoResettable<StyledStr>) -> Command

Sets the program’s description for the short help (-h).

If Command::long_about is not specified, this message will be displayed for --help.

NOTE: Only Command::about (short format) is used in completion script generation in order to be concise.

See also crate_description!.

Examples

Command::new("myprog")
    .about("Does really amazing things for great people")

pub fn long_about(self, long_about: impl IntoResettable<StyledStr>) -> Command

Sets the program’s description for the long help (--help).

If Command::about is not specified, this message will be displayed for -h.

NOTE: Only Command::about (short format) is used in completion script generation in order to be concise.

Examples

Command::new("myprog")
    .long_about(
"Does really amazing things to great people. Now let's talk a little
 more in depth about how this subcommand really works. It may take about
 a few lines of text, but that's ok!")

pub fn after_help(self, help: impl IntoResettable<StyledStr>) -> Command

Free-form help text for after auto-generated short help (-h).

This is often used to describe how to use the arguments, caveats to be noted, or license and contact information.

If Command::after_long_help is not specified, this message will be displayed for --help.

Examples

Command::new("myprog")
    .after_help("Does really amazing things for great people... but be careful with -R!")

pub fn after_long_help(self, help: impl IntoResettable<StyledStr>) -> Command

Free-form help text for after auto-generated long help (--help).

This is often used to describe how to use the arguments, caveats to be noted, or license and contact information.

If Command::after_help is not specified, this message will be displayed for -h.

Examples

Command::new("myprog")
    .after_long_help("Does really amazing things to great people... but be careful with -R, \
                     like, for real, be careful with this!")

pub fn before_help(self, help: impl IntoResettable<StyledStr>) -> Command

Free-form help text for before auto-generated short help (-h).

This is often used for header, copyright, or license information.

If Command::before_long_help is not specified, this message will be displayed for --help.

Examples

Command::new("myprog")
    .before_help("Some info I'd like to appear before the help info")

pub fn before_long_help(self, help: impl IntoResettable<StyledStr>) -> Command

Free-form help text for before auto-generated long help (--help).

This is often used for header, copyright, or license information.

If Command::before_help is not specified, this message will be displayed for -h.

Examples

Command::new("myprog")
    .before_long_help("Some verbose and long info I'd like to appear before the help info")

pub fn version(self, ver: impl IntoResettable<Str>) -> Command

Sets the version for the short version (-V) and help messages.

If Command::long_version is not specified, this message will be displayed for --version.

Pro-tip: Use claps convenience macro crate_version! to automatically set your application’s version to the same thing as your crate at compile time.

Examples

Command::new("myprog")
    .version("v0.1.24")

pub fn long_version(self, ver: impl IntoResettable<Str>) -> Command

Sets the version for the long version (--version) and help messages.

If Command::version is not specified, this message will be displayed for -V.

Pro-tip: Use claps convenience macro crate_version! to automatically set your application’s version to the same thing as your crate at compile time.

Examples

Command::new("myprog")
    .long_version(
"v0.1.24
 commit: abcdef89726d
 revision: 123
 release: 2
 binary: myprog")

pub fn override_usage(self, usage: impl IntoResettable<StyledStr>) -> Command

Overrides the clap generated usage string for help and error messages.

NOTE: Using this setting disables claps “context-aware” usage strings. After this setting is set, this will be the only usage string displayed to the user!

NOTE: Multiple usage lines may be present in the usage argument, but some rules need to be followed to ensure the usage lines are formatted correctly by the default help formatter:

• Do not indent the first usage line.
• Indent all subsequent usage lines with seven spaces.
• The last line must not end with a newline.

Examples

Command::new("myprog")
    .override_usage("myapp [-clDas] <some_file>")

Or for multiple usage lines:

Command::new("myprog")
    .override_usage(
        "myapp -X [-a] [-b] <file>\n       \
         myapp -Y [-c] <file1> <file2>\n       \
         myapp -Z [-d|-e]"
    )

pub fn override_help(self, help: impl IntoResettable<StyledStr>) -> Command

Overrides the clap generated help message (both -h and --help).

This should only be used when the auto-generated message does not suffice.

NOTE: This only replaces the help message for the current command, meaning if you are using subcommands, those help messages will still be auto-generated unless you specify a Command::override_help for them as well.

Examples

Command::new("myapp")
    .override_help("myapp v1.0\n\
           Does awesome things\n\
           (C) me@mail.com\n\n\

           Usage: myapp <opts> <command>\n\n\

           Options:\n\
           -h, --help       Display this message\n\
           -V, --version    Display version info\n\
           -s <stuff>       Do something with stuff\n\
           -v               Be verbose\n\n\

           Commands:\n\
           help             Print this message\n\
           work             Do some work")

pub fn help_template(self, s: impl IntoResettable<StyledStr>) -> Command

Available on crate feature help only.

Sets the help template to be used, overriding the default format.

NOTE: The template system is by design very simple. Therefore, the tags have to be written in the lowercase and without spacing.

Tags are given inside curly brackets.

Valid tags are:

• {name} - Display name for the (sub-)command.
• {bin} - Binary name.(deprecated)
• {version} - Version number.
• {author} - Author information.
• {author-with-newline} - Author followed by \n.
• {author-section} - Author preceded and followed by \n.
• {about} - General description (from Command::about or Command::long_about).
• {about-with-newline} - About followed by \n.
• {about-section} - About preceded and followed by ‘\n’.
• {usage-heading} - Automatically generated usage heading.
• {usage} - Automatically generated or given usage string.
• {all-args} - Help for all arguments (options, flags, positional arguments, and subcommands) including titles.
• {options} - Help for options.
• {positionals} - Help for positional arguments.
• {subcommands} - Help for subcommands.
• {tab} - Standard tab sized used within clap
• {after-help} - Help from Command::after_help or Command::after_long_help.
• {before-help} - Help from Command::before_help or Command::before_long_help.

Examples

For a very brief help:

Command::new("myprog")
    .version("1.0")
    .help_template("{name} ({version}) - {usage}")

For showing more application context:

Command::new("myprog")
    .version("1.0")
    .help_template("\
{before-help}{name} {version}
{author-with-newline}{about-with-newline}
{usage-heading} {usage}

{all-args}{after-help}
")

pub fn next_help_heading(self, heading: impl IntoResettable<Str>) -> Command

Set the default section heading for future args.

This will be used for any arg that hasn’t had Arg::help_heading called.

This is useful if the default Options or Arguments headings are not specific enough for one’s use case.

For subcommands, see Command::subcommand_help_heading

pub fn next_display_order(self, disp_ord: impl IntoResettable<usize>) -> Command

Change the starting value for assigning future display orders for args.

This will be used for any arg that hasn’t had Arg::display_order called.

pub fn arg_required_else_help(self, yes: bool) -> Command

Exit gracefully if no arguments are present (e.g. $ myprog).

NOTE: subcommands count as arguments

Examples

Command::new("myprog")
    .arg_required_else_help(true);

pub fn allow_missing_positional(self, yes: bool) -> Command

Allows one to implement two styles of CLIs where positionals can be used out of order.

The first example is a CLI where the second to last positional argument is optional, but the final positional argument is required. Such as $ prog [optional] <required> where one of the two following usages is allowed:

• $ prog [optional] <required>
• $ prog <required>

This would otherwise not be allowed. This is useful when [optional] has a default value.

Note: when using this style of “missing positionals” the final positional must be required if -- will not be used to skip to the final positional argument.

Note: This style also only allows a single positional argument to be “skipped” without the use of --. To skip more than one, see the second example.

The second example is when one wants to skip multiple optional positional arguments, and use of the -- operator is OK (but not required if all arguments will be specified anyways).

For example, imagine a CLI which has three positional arguments [foo] [bar] [baz]... where baz accepts multiple values (similar to man ARGS... style training arguments).

With this setting the following invocations are posisble:

• $ prog foo bar baz1 baz2 baz3
• $ prog foo -- baz1 baz2 baz3
• $ prog -- baz1 baz2 baz3

Examples

Style number one from above:

// Assume there is an external subcommand named "subcmd"
let m = Command::new("myprog")
    .allow_missing_positional(true)
    .arg(Arg::new("arg1"))
    .arg(Arg::new("arg2")
        .required(true))
    .get_matches_from(vec![
        "prog", "other"
    ]);

assert_eq!(m.get_one::<String>("arg1"), None);
assert_eq!(m.get_one::<String>("arg2").unwrap(), "other");

Now the same example, but using a default value for the first optional positional argument

// Assume there is an external subcommand named "subcmd"
let m = Command::new("myprog")
    .allow_missing_positional(true)
    .arg(Arg::new("arg1")
        .default_value("something"))
    .arg(Arg::new("arg2")
        .required(true))
    .get_matches_from(vec![
        "prog", "other"
    ]);

assert_eq!(m.get_one::<String>("arg1").unwrap(), "something");
assert_eq!(m.get_one::<String>("arg2").unwrap(), "other");

Style number two from above:

// Assume there is an external subcommand named "subcmd"
let m = Command::new("myprog")
    .allow_missing_positional(true)
    .arg(Arg::new("foo"))
    .arg(Arg::new("bar"))
    .arg(Arg::new("baz").action(ArgAction::Set).num_args(1..))
    .get_matches_from(vec![
        "prog", "foo", "bar", "baz1", "baz2", "baz3"
    ]);

assert_eq!(m.get_one::<String>("foo").unwrap(), "foo");
assert_eq!(m.get_one::<String>("bar").unwrap(), "bar");
assert_eq!(m.get_many::<String>("baz").unwrap().collect::<Vec<_>>(), &["baz1", "baz2", "baz3"]);

Now nofice if we don’t specify foo or baz but use the -- operator.

// Assume there is an external subcommand named "subcmd"
let m = Command::new("myprog")
    .allow_missing_positional(true)
    .arg(Arg::new("foo"))
    .arg(Arg::new("bar"))
    .arg(Arg::new("baz").action(ArgAction::Set).num_args(1..))
    .get_matches_from(vec![
        "prog", "--", "baz1", "baz2", "baz3"
    ]);

assert_eq!(m.get_one::<String>("foo"), None);
assert_eq!(m.get_one::<String>("bar"), None);
assert_eq!(m.get_many::<String>("baz").unwrap().collect::<Vec<_>>(), &["baz1", "baz2", "baz3"]);

impl Command

Subcommand-specific Settings

pub fn short_flag(self, short: impl IntoResettable<char>) -> Command

Sets the short version of the subcommand flag without the preceding -.

Allows the subcommand to be used as if it were an Arg::short.

Examples

let matches = Command::new("pacman")
    .subcommand(
        Command::new("sync").short_flag('S').arg(
            Arg::new("search")
                .short('s')
                .long("search")
                .action(ArgAction::SetTrue)
                .help("search remote repositories for matching strings"),
        ),
    )
    .get_matches_from(vec!["pacman", "-Ss"]);

assert_eq!(matches.subcommand_name().unwrap(), "sync");
let sync_matches = matches.subcommand_matches("sync").unwrap();
assert!(sync_matches.get_flag("search"));

pub fn long_flag(self, long: impl Into<Str>) -> Command

Sets the long version of the subcommand flag without the preceding --.

Allows the subcommand to be used as if it were an Arg::long.

NOTE: Any leading - characters will be stripped.

Examples

To set long_flag use a word containing valid UTF-8 codepoints. If you supply a double leading -- such as --sync they will be stripped. Hyphens in the middle of the word; however, will not be stripped (i.e. sync-file is allowed).

let matches = Command::new("pacman")
    .subcommand(
        Command::new("sync").long_flag("sync").arg(
            Arg::new("search")
                .short('s')
                .long("search")
                .action(ArgAction::SetTrue)
                .help("search remote repositories for matching strings"),
        ),
    )
    .get_matches_from(vec!["pacman", "--sync", "--search"]);

assert_eq!(matches.subcommand_name().unwrap(), "sync");
let sync_matches = matches.subcommand_matches("sync").unwrap();
assert!(sync_matches.get_flag("search"));

pub fn alias(self, name: impl IntoResettable<Str>) -> Command

Sets a hidden alias to this subcommand.

This allows the subcommand to be accessed via either the original name, or this given alias. This is more efficient and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command, and not all aliased variants.

NOTE: Aliases defined with this method are hidden from the help message. If you’re looking for aliases that will be displayed in the help message, see Command::visible_alias.

NOTE: When using aliases and checking for the existence of a particular subcommand within an ArgMatches struct, one only needs to search for the original name and not all aliases.

Examples

let m = Command::new("myprog")
    .subcommand(Command::new("test")
        .alias("do-stuff"))
    .get_matches_from(vec!["myprog", "do-stuff"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn short_flag_alias(self, name: impl IntoResettable<char>) -> Command

Add an alias, which functions as “hidden” short flag subcommand

This will automatically dispatch as if this subcommand was used. This is more efficient, and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command, and not all variants.

Examples

let m = Command::new("myprog")
            .subcommand(Command::new("test").short_flag('t')
                .short_flag_alias('d'))
            .get_matches_from(vec!["myprog", "-d"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn long_flag_alias(self, name: impl IntoResettable<Str>) -> Command

Add an alias, which functions as a “hidden” long flag subcommand.

This will automatically dispatch as if this subcommand was used. This is more efficient, and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command, and not all variants.

Examples

let m = Command::new("myprog")
            .subcommand(Command::new("test").long_flag("test")
                .long_flag_alias("testing"))
            .get_matches_from(vec!["myprog", "--testing"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn aliases(self, names: impl IntoIterator<Item = impl Into<Str>>) -> Command

Sets multiple hidden aliases to this subcommand.

This allows the subcommand to be accessed via either the original name or any of the given aliases. This is more efficient, and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command and not all aliased variants.

NOTE: Aliases defined with this method are hidden from the help message. If looking for aliases that will be displayed in the help message, see Command::visible_aliases.

NOTE: When using aliases and checking for the existence of a particular subcommand within an ArgMatches struct, one only needs to search for the original name and not all aliases.

Examples

let m = Command::new("myprog")
    .subcommand(Command::new("test")
        .aliases(["do-stuff", "do-tests", "tests"]))
        .arg(Arg::new("input")
            .help("the file to add")
            .required(false))
    .get_matches_from(vec!["myprog", "do-tests"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn short_flag_aliases( self, names: impl IntoIterator<Item = char> ) -> Command

Add aliases, which function as “hidden” short flag subcommands.

These will automatically dispatch as if this subcommand was used. This is more efficient, and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command, and not all variants.

Examples

let m = Command::new("myprog")
    .subcommand(Command::new("test").short_flag('t')
        .short_flag_aliases(['a', 'b', 'c']))
        .arg(Arg::new("input")
            .help("the file to add")
            .required(false))
    .get_matches_from(vec!["myprog", "-a"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn long_flag_aliases( self, names: impl IntoIterator<Item = impl Into<Str>> ) -> Command

Add aliases, which function as “hidden” long flag subcommands.

These will automatically dispatch as if this subcommand was used. This is more efficient, and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command, and not all variants.

Examples

let m = Command::new("myprog")
            .subcommand(Command::new("test").long_flag("test")
                .long_flag_aliases(["testing", "testall", "test_all"]))
                .arg(Arg::new("input")
                            .help("the file to add")
                            .required(false))
            .get_matches_from(vec!["myprog", "--testing"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn visible_alias(self, name: impl IntoResettable<Str>) -> Command

Sets a visible alias to this subcommand.

This allows the subcommand to be accessed via either the original name or the given alias. This is more efficient and easier than creating hidden subcommands as one only needs to check for the existence of this command and not all aliased variants.

NOTE: The alias defined with this method is visible from the help message and displayed as if it were just another regular subcommand. If looking for an alias that will not be displayed in the help message, see Command::alias.

NOTE: When using aliases and checking for the existence of a particular subcommand within an ArgMatches struct, one only needs to search for the original name and not all aliases.

Examples

let m = Command::new("myprog")
    .subcommand(Command::new("test")
        .visible_alias("do-stuff"))
    .get_matches_from(vec!["myprog", "do-stuff"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn visible_short_flag_alias( self, name: impl IntoResettable<char> ) -> Command

Add an alias, which functions as “visible” short flag subcommand

This will automatically dispatch as if this subcommand was used. This is more efficient, and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command, and not all variants.

See also Command::short_flag_alias.

Examples

let m = Command::new("myprog")
            .subcommand(Command::new("test").short_flag('t')
                .visible_short_flag_alias('d'))
            .get_matches_from(vec!["myprog", "-d"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn visible_long_flag_alias(self, name: impl IntoResettable<Str>) -> Command

Add an alias, which functions as a “visible” long flag subcommand.

This will automatically dispatch as if this subcommand was used. This is more efficient, and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command, and not all variants.

See also Command::long_flag_alias.

Examples

let m = Command::new("myprog")
            .subcommand(Command::new("test").long_flag("test")
                .visible_long_flag_alias("testing"))
            .get_matches_from(vec!["myprog", "--testing"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn visible_aliases( self, names: impl IntoIterator<Item = impl Into<Str>> ) -> Command

Sets multiple visible aliases to this subcommand.

This allows the subcommand to be accessed via either the original name or any of the given aliases. This is more efficient and easier than creating multiple hidden subcommands as one only needs to check for the existence of this command and not all aliased variants.

NOTE: The alias defined with this method is visible from the help message and displayed as if it were just another regular subcommand. If looking for an alias that will not be displayed in the help message, see Command::alias.

NOTE: When using aliases, and checking for the existence of a particular subcommand within an ArgMatches struct, one only needs to search for the original name and not all aliases.

Examples

let m = Command::new("myprog")
    .subcommand(Command::new("test")
        .visible_aliases(["do-stuff", "tests"]))
    .get_matches_from(vec!["myprog", "do-stuff"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn visible_short_flag_aliases( self, names: impl IntoIterator<Item = char> ) -> Command

Add aliases, which function as visible short flag subcommands.

See Command::short_flag_aliases.

Examples

let m = Command::new("myprog")
            .subcommand(Command::new("test").short_flag('b')
                .visible_short_flag_aliases(['t']))
            .get_matches_from(vec!["myprog", "-t"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn visible_long_flag_aliases( self, names: impl IntoIterator<Item = impl Into<Str>> ) -> Command

Add aliases, which function as visible long flag subcommands.

See Command::long_flag_aliases.

Examples

let m = Command::new("myprog")
            .subcommand(Command::new("test").long_flag("test")
                .visible_long_flag_aliases(["testing", "testall", "test_all"]))
            .get_matches_from(vec!["myprog", "--testing"]);
assert_eq!(m.subcommand_name(), Some("test"));

pub fn display_order(self, ord: impl IntoResettable<usize>) -> Command

Set the placement of this subcommand within the help.

Subcommands with a lower value will be displayed first in the help message. Those with the same display order will be sorted.

Commands are automatically assigned a display order based on the order they are added to their parent Command. Overriding this is helpful when the order commands are added in isn’t the same as the display order, whether in one-off cases or to automatically sort commands.

Examples

let m = Command::new("cust-ord")
    .subcommand(Command::new("beta")
        .display_order(0)  // Sort
        .about("Some help and text"))
    .subcommand(Command::new("alpha")
        .display_order(0)  // Sort
        .about("I should be first!"))
    .get_matches_from(vec![
        "cust-ord", "--help"
    ]);

The above example displays the following help message

cust-ord

Usage: cust-ord [OPTIONS]

Commands:
    alpha    I should be first!
    beta     Some help and text
    help     Print help for the subcommand(s)

Options:
    -h, --help       Print help
    -V, --version    Print version

pub fn hide(self, yes: bool) -> Command

Specifies that this subcommand should be hidden from help messages

Examples

Command::new("myprog")
    .subcommand(
        Command::new("test").hide(true)
    )

pub fn subcommand_required(self, yes: bool) -> Command

If no subcommand is present at runtime, error and exit gracefully.

Examples

let err = Command::new("myprog")
    .subcommand_required(true)
    .subcommand(Command::new("test"))
    .try_get_matches_from(vec![
        "myprog",
    ]);
assert!(err.is_err());
assert_eq!(err.unwrap_err().kind(), ErrorKind::MissingSubcommand);

pub fn allow_external_subcommands(self, yes: bool) -> Command

Assume unexpected positional arguments are a subcommand.

Arguments will be stored in the "" argument in the ArgMatches

NOTE: Use this setting with caution, as a truly unexpected argument (i.e. one that is NOT an external subcommand) will not cause an error and instead be treated as a potential subcommand. One should check for such cases manually and inform the user appropriately.

NOTE: A built-in subcommand will be parsed as an external subcommand when escaped with --.

Examples

// Assume there is an external subcommand named "subcmd"
let m = Command::new("myprog")
    .allow_external_subcommands(true)
    .get_matches_from(vec![
        "myprog", "subcmd", "--option", "value", "-fff", "--flag"
    ]);

// All trailing arguments will be stored under the subcommand's sub-matches using an empty
// string argument name
match m.subcommand() {
    Some((external, ext_m)) => {
         let ext_args: Vec<_> = ext_m.get_many::<OsString>("").unwrap().collect();
         assert_eq!(external, "subcmd");
         assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    },
    _ => {},
}

pub fn external_subcommand_value_parser( self, parser: impl IntoResettable<ValueParser> ) -> Command

Specifies how to parse external subcommand arguments.

The default parser is for OsString. This can be used to switch it to String or another type.

NOTE: Setting this requires Command::allow_external_subcommands

Examples

// Assume there is an external subcommand named "subcmd"
let m = Command::new("myprog")
    .allow_external_subcommands(true)
    .get_matches_from(vec![
        "myprog", "subcmd", "--option", "value", "-fff", "--flag"
    ]);

// All trailing arguments will be stored under the subcommand's sub-matches using an empty
// string argument name
match m.subcommand() {
    Some((external, ext_m)) => {
         let ext_args: Vec<_> = ext_m.get_many::<OsString>("").unwrap().collect();
         assert_eq!(external, "subcmd");
         assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    },
    _ => {},
}

// Assume there is an external subcommand named "subcmd"
let m = Command::new("myprog")
    .external_subcommand_value_parser(value_parser!(String))
    .get_matches_from(vec![
        "myprog", "subcmd", "--option", "value", "-fff", "--flag"
    ]);

// All trailing arguments will be stored under the subcommand's sub-matches using an empty
// string argument name
match m.subcommand() {
    Some((external, ext_m)) => {
         let ext_args: Vec<_> = ext_m.get_many::<String>("").unwrap().collect();
         assert_eq!(external, "subcmd");
         assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    },
    _ => {},
}

pub fn args_conflicts_with_subcommands(self, yes: bool) -> Command

Specifies that use of an argument prevents the use of subcommands.

By default clap allows arguments between subcommands such as <cmd> [cmd_args] <subcmd> [subcmd_args] <subsubcmd> [subsubcmd_args].

This setting disables that functionality and says that arguments can only follow the final subcommand. For instance using this setting makes only the following invocations possible:

• <cmd> <subcmd> <subsubcmd> [subsubcmd_args]
• <cmd> <subcmd> [subcmd_args]
• <cmd> [cmd_args]

Examples

Command::new("myprog")
    .args_conflicts_with_subcommands(true);

pub fn subcommand_precedence_over_arg(self, yes: bool) -> Command

Prevent subcommands from being consumed as an arguments value.

By default, if an option taking multiple values is followed by a subcommand, the subcommand will be parsed as another value.

cmd --foo val1 val2 subcommand
          --------- ----------
            values   another value

This setting instructs the parser to stop when encountering a subcommand instead of greedily consuming arguments.

cmd --foo val1 val2 subcommand
          --------- ----------
            values   subcommand

Examples

let cmd = Command::new("cmd").subcommand(Command::new("sub")).arg(
    Arg::new("arg")
        .long("arg")
        .num_args(1..)
        .action(ArgAction::Set),
);

let matches = cmd
    .clone()
    .try_get_matches_from(&["cmd", "--arg", "1", "2", "3", "sub"])
    .unwrap();
assert_eq!(
    matches.get_many::<String>("arg").unwrap().collect::<Vec<_>>(),
    &["1", "2", "3", "sub"]
);
assert!(matches.subcommand_matches("sub").is_none());

let matches = cmd
    .subcommand_precedence_over_arg(true)
    .try_get_matches_from(&["cmd", "--arg", "1", "2", "3", "sub"])
    .unwrap();
assert_eq!(
    matches.get_many::<String>("arg").unwrap().collect::<Vec<_>>(),
    &["1", "2", "3"]
);
assert!(matches.subcommand_matches("sub").is_some());

pub fn subcommand_negates_reqs(self, yes: bool) -> Command

Allows subcommands to override all requirements of the parent command.

For example, if you had a subcommand or top level application with a required argument that is only required as long as there is no subcommand present, using this setting would allow you to set those arguments to Arg::required(true) and yet receive no error so long as the user uses a valid subcommand instead.

NOTE: This defaults to false (using subcommand does not negate requirements)

Examples

This first example shows that it is an error to not use a required argument

let err = Command::new("myprog")
    .subcommand_negates_reqs(true)
    .arg(Arg::new("opt").required(true))
    .subcommand(Command::new("test"))
    .try_get_matches_from(vec![
        "myprog"
    ]);
assert!(err.is_err());
assert_eq!(err.unwrap_err().kind(), ErrorKind::MissingRequiredArgument);

This next example shows that it is no longer error to not use a required argument if a valid subcommand is used.

let noerr = Command::new("myprog")
    .subcommand_negates_reqs(true)
    .arg(Arg::new("opt").required(true))
    .subcommand(Command::new("test"))
    .try_get_matches_from(vec![
        "myprog", "test"
    ]);
assert!(noerr.is_ok());

pub fn multicall(self, yes: bool) -> Command

Multiple-personality program dispatched on the binary name (argv[0])

A “multicall” executable is a single executable that contains a variety of applets, and decides which applet to run based on the name of the file. The executable can be called from different names by creating hard links or symbolic links to it.

This is desirable for:

• Easy distribution, a single binary that can install hardlinks to access the different personalities.
• Minimal binary size by sharing common code (e.g. standard library, clap)
• Custom shells or REPLs where there isn’t a single top-level command

Setting multicall will cause

• argv[0] to be stripped to the base name and parsed as the first argument, as if Command::no_binary_name was set.
• Help and errors to report subcommands as if they were the top-level command

When the subcommand is not present, there are several strategies you may employ, depending on your needs:

• Let the error percolate up normally
• Print a specialized error message using the Error::context
• Print the help but this might be ambiguous
• Disable multicall and re-parse it
• Disable multicall and re-parse it with a specific subcommand

When detecting the error condition, the ErrorKind isn’t sufficient as a sub-subcommand might report the same error. Enable allow_external_subcommands if you want to specifically get the unrecognized binary name.

NOTE: Multicall can’t be used with no_binary_name since they interpret the command name in incompatible ways.

NOTE: The multicall command cannot have arguments.

NOTE: Applets are slightly semantically different from subcommands, so it’s recommended to use Command::subcommand_help_heading and Command::subcommand_value_name to change the descriptive text as above.

Examples

hostname is an example of a multicall executable. Both hostname and dnsdomainname are provided by the same executable and which behaviour to use is based on the executable file name.

This is desirable when the executable has a primary purpose but there is related functionality that would be convenient to provide and implement it to be in the same executable.

The name of the cmd is essentially unused and may be the same as the name of a subcommand.

The names of the immediate subcommands of the Command are matched against the basename of the first argument, which is conventionally the path of the executable.

This does not allow the subcommand to be passed as the first non-path argument.

let mut cmd = Command::new("hostname")
    .multicall(true)
    .subcommand(Command::new("hostname"))
    .subcommand(Command::new("dnsdomainname"));
let m = cmd.try_get_matches_from_mut(&["/usr/bin/hostname", "dnsdomainname"]);
assert!(m.is_err());
assert_eq!(m.unwrap_err().kind(), ErrorKind::UnknownArgument);
let m = cmd.get_matches_from(&["/usr/bin/dnsdomainname"]);
assert_eq!(m.subcommand_name(), Some("dnsdomainname"));

Busybox is another common example of a multicall executable with a subcommmand for each applet that can be run directly, e.g. with the cat applet being run by running busybox cat, or with cat as a link to the busybox binary.

This is desirable when the launcher program has additional options or it is useful to run the applet without installing a symlink e.g. to test the applet without installing it or there may already be a command of that name installed.

To make an applet usable as both a multicall link and a subcommand the subcommands must be defined both in the top-level Command and as subcommands of the “main” applet.

fn applet_commands() -> [Command; 2] {
    [Command::new("true"), Command::new("false")]
}
let mut cmd = Command::new("busybox")
    .multicall(true)
    .subcommand(
        Command::new("busybox")
            .subcommand_value_name("APPLET")
            .subcommand_help_heading("APPLETS")
            .subcommands(applet_commands()),
    )
    .subcommands(applet_commands());
// When called from the executable's canonical name
// its applets can be matched as subcommands.
let m = cmd.try_get_matches_from_mut(&["/usr/bin/busybox", "true"]).unwrap();
assert_eq!(m.subcommand_name(), Some("busybox"));
assert_eq!(m.subcommand().unwrap().1.subcommand_name(), Some("true"));
// When called from a link named after an applet that applet is matched.
let m = cmd.get_matches_from(&["/usr/bin/true"]);
assert_eq!(m.subcommand_name(), Some("true"));

pub fn subcommand_value_name( self, value_name: impl IntoResettable<Str> ) -> Command

Sets the value name used for subcommands when printing usage and help.

By default, this is “COMMAND”.

See also Command::subcommand_help_heading

Examples

Command::new("myprog")
    .subcommand(Command::new("sub1"))
    .print_help()

will produce

myprog

Usage: myprog [COMMAND]

Commands:
    help    Print this message or the help of the given subcommand(s)
    sub1

Options:
    -h, --help       Print help
    -V, --version    Print version

but usage of subcommand_value_name

Command::new("myprog")
    .subcommand(Command::new("sub1"))
    .subcommand_value_name("THING")
    .print_help()

will produce

myprog

Usage: myprog [THING]

Commands:
    help    Print this message or the help of the given subcommand(s)
    sub1

Options:
    -h, --help       Print help
    -V, --version    Print version

pub fn subcommand_help_heading( self, heading: impl IntoResettable<Str> ) -> Command

Sets the help heading used for subcommands when printing usage and help.

By default, this is “Commands”.

See also Command::subcommand_value_name

Examples

Command::new("myprog")
    .subcommand(Command::new("sub1"))
    .print_help()

will produce

myprog

Usage: myprog [COMMAND]

Commands:
    help    Print this message or the help of the given subcommand(s)
    sub1

Options:
    -h, --help       Print help
    -V, --version    Print version

but usage of subcommand_help_heading

Command::new("myprog")
    .subcommand(Command::new("sub1"))
    .subcommand_help_heading("Things")
    .print_help()

will produce

myprog

Usage: myprog [COMMAND]

Things:
    help    Print this message or the help of the given subcommand(s)
    sub1

Options:
    -h, --help       Print help
    -V, --version    Print version

impl Command

Reflection

pub fn get_display_name(&self) -> Option<&str>

Get the name of the binary.

pub fn get_bin_name(&self) -> Option<&str>

Get the name of the binary.

pub fn set_bin_name(&mut self, name: impl Into<String>)

Set binary name. Uses &mut self instead of self.

pub fn get_name(&self) -> &str

Get the name of the cmd.

pub fn get_version(&self) -> Option<&str>

Get the version of the cmd.

pub fn get_long_version(&self) -> Option<&str>

Get the long version of the cmd.

pub fn get_author(&self) -> Option<&str>

Get the authors of the cmd.

pub fn get_short_flag(&self) -> Option<char>

Get the short flag of the subcommand.

pub fn get_long_flag(&self) -> Option<&str>

Get the long flag of the subcommand.

pub fn get_about(&self) -> Option<&StyledStr>

Get the help message specified via Command::about.

pub fn get_long_about(&self) -> Option<&StyledStr>

Get the help message specified via Command::long_about.

pub fn get_next_help_heading(&self) -> Option<&str>

Get the custom section heading specified via Command::next_help_heading.

pub fn get_visible_aliases(&self) -> impl Iterator<Item = &str>

Iterate through the visible aliases for this subcommand.

pub fn get_visible_short_flag_aliases(&self) -> impl Iterator<Item = char>

Iterate through the visible short aliases for this subcommand.

pub fn get_visible_long_flag_aliases(&self) -> impl Iterator<Item = &str>

Iterate through the visible long aliases for this subcommand.

pub fn get_all_aliases(&self) -> impl Iterator<Item = &str>

Iterate through the set of all the aliases for this subcommand, both visible and hidden.

pub fn get_all_short_flag_aliases(&self) -> impl Iterator<Item = char>

Iterate through the set of all the short aliases for this subcommand, both visible and hidden.

pub fn get_all_long_flag_aliases(&self) -> impl Iterator<Item = &str>

Iterate through the set of all the long aliases for this subcommand, both visible and hidden.

pub fn get_color(&self) -> ColorChoice

Should we color the output?

pub fn get_styles(&self) -> &Styles

Return the current Styles for the Command

pub fn get_subcommands(&self) -> impl Iterator<Item = &Command>

Iterate through the set of subcommands, getting a reference to each.

pub fn get_subcommands_mut(&mut self) -> impl Iterator<Item = &mut Command>

Iterate through the set of subcommands, getting a mutable reference to each.

pub fn has_subcommands(&self) -> bool

Returns true if this Command has subcommands.

pub fn get_subcommand_help_heading(&self) -> Option<&str>

Returns the help heading for listing subcommands.

pub fn get_subcommand_value_name(&self) -> Option<&str>

Returns the subcommand value name.

pub fn get_before_help(&self) -> Option<&StyledStr>

Returns the help heading for listing subcommands.

pub fn get_before_long_help(&self) -> Option<&StyledStr>

Returns the help heading for listing subcommands.

pub fn get_after_help(&self) -> Option<&StyledStr>

Returns the help heading for listing subcommands.

pub fn get_after_long_help(&self) -> Option<&StyledStr>

Returns the help heading for listing subcommands.

pub fn find_subcommand(&self, name: impl AsRef<OsStr>) -> Option<&Command>

Find subcommand such that its name or one of aliases equals name.

This does not recurse through subcommands of subcommands.

pub fn find_subcommand_mut( &mut self, name: impl AsRef<OsStr> ) -> Option<&mut Command>

Find subcommand such that its name or one of aliases equals name, returning a mutable reference to the subcommand.

This does not recurse through subcommands of subcommands.

pub fn get_groups(&self) -> impl Iterator<Item = &ArgGroup>

Iterate through the set of groups.

pub fn get_arguments(&self) -> impl Iterator<Item = &Arg>

Iterate through the set of arguments.

pub fn get_positionals(&self) -> impl Iterator<Item = &Arg>

Iterate through the positionals arguments.

pub fn get_opts(&self) -> impl Iterator<Item = &Arg>

Iterate through the options.

pub fn get_arg_conflicts_with(&self, arg: &Arg) -> Vec<&Arg, Global>

Get a list of all arguments the given argument conflicts with.

If the provided argument is declared as global, the conflicts will be determined based on the propagation rules of global arguments.

Panics

If the given arg contains a conflict with an argument that is unknown to this Command.

pub fn is_no_binary_name_set(&self) -> bool

Report whether Command::no_binary_name is set

pub fn is_dont_delimit_trailing_values_set(&self) -> bool

Report whether Command::dont_delimit_trailing_values is set

pub fn is_disable_version_flag_set(&self) -> bool

Report whether Command::disable_version_flag is set

pub fn is_propagate_version_set(&self) -> bool

Report whether Command::propagate_version is set

pub fn is_next_line_help_set(&self) -> bool

Report whether Command::next_line_help is set

pub fn is_disable_help_flag_set(&self) -> bool

Report whether Command::disable_help_flag is set

pub fn is_disable_help_subcommand_set(&self) -> bool

Report whether Command::disable_help_subcommand is set

pub fn is_disable_colored_help_set(&self) -> bool

Report whether Command::disable_colored_help is set

pub fn is_arg_required_else_help_set(&self) -> bool

Report whether Command::arg_required_else_help is set

pub fn is_allow_missing_positional_set(&self) -> bool

Report whether Command::allow_missing_positional is set

pub fn is_hide_set(&self) -> bool

Report whether Command::hide is set

pub fn is_subcommand_required_set(&self) -> bool

Report whether Command::subcommand_required is set

pub fn is_allow_external_subcommands_set(&self) -> bool

Report whether Command::allow_external_subcommands is set

pub fn get_external_subcommand_value_parser(&self) -> Option<&ValueParser>

Configured parser for values passed to an external subcommand

Example

let cmd = clap::Command::new("raw")
    .external_subcommand_value_parser(clap::value_parser!(String));
let value_parser = cmd.get_external_subcommand_value_parser();
println!("{value_parser:?}");

pub fn is_args_conflicts_with_subcommands_set(&self) -> bool

Report whether Command::args_conflicts_with_subcommands is set

pub fn is_subcommand_precedence_over_arg_set(&self) -> bool

Report whether Command::subcommand_precedence_over_arg is set

pub fn is_subcommand_negates_reqs_set(&self) -> bool

Report whether Command::subcommand_negates_reqs is set

pub fn is_multicall_set(&self) -> bool

Report whether Command::multicall is set

impl Command

pub fn build(&mut self)

Prepare for introspecting on all included Commands

Call this on the top-level Command when done building and before reading state for cases like completions, custom help output, etc.

Trait Implementations

impl Clone for Command

fn clone(&self) -> Command

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Command

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for Command

fn default() -> Command

Returns the “default value” for a type.

impl Display for Command

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl From<&Command> for Command

fn from(cmd: &Command) -> Command

Converts to this type from the input type.

impl Index<&Id> for Command

type Output = Arg

The returned type after indexing.

fn index(&self, key: &Id) -> &<Command as Index<&Id>>::Output

Performs the indexing (container[index]) operation.