clap::builder

Enum ArgAction

Source
#[non_exhaustive]
pub enum ArgAction { Set, Append, SetTrue, SetFalse, Count, Help, HelpShort, HelpLong, Version, }
Expand description

Behavior of arguments when they are encountered while parsing

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("special-help")
            .short('?')
            .action(clap::ArgAction::Help)
    );

// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);

// New help available
let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);

Variants (Non-exhaustive)§

This enum is marked as non-exhaustive
Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.
§

Set

When encountered, store the associated value(s) in ArgMatches

NOTE: If the argument has previously been seen, it will result in a ArgumentConflict unless Command::args_override_self(true) is set.

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .action(clap::ArgAction::Set)
    );

let matches = cmd.try_get_matches_from(["mycmd", "--flag", "value"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_many::<String>("flag").unwrap_or_default().map(|v| v.as_str()).collect::<Vec<_>>(),
    vec!["value"]
);
§

Append

When encountered, store the associated value(s) in ArgMatches

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .action(clap::ArgAction::Append)
    );

let matches = cmd.try_get_matches_from(["mycmd", "--flag", "value1", "--flag", "value2"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_many::<String>("flag").unwrap_or_default().map(|v| v.as_str()).collect::<Vec<_>>(),
    vec!["value1", "value2"]
);
§

SetTrue

When encountered, act as if "true" was encountered on the command-line

If no default_value is set, it will be false.

No value is allowed. To optionally accept a value, see Arg::default_missing_value

NOTE: If the argument has previously been seen, it will result in a ArgumentConflict unless Command::args_override_self(true) is set.

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .action(clap::ArgAction::SetTrue)
    );

let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_flag("flag"),
    true
);

let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_flag("flag"),
    false
);

You can use TypedValueParser::map to have the flag control an application-specific type:

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .action(clap::ArgAction::SetTrue)
            .value_parser(
                BoolishValueParser::new()
                .map(|b| -> usize {
                    if b { 10 } else { 5 }
                })
            )
    );

let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_one::<usize>("flag").copied(),
    Some(10)
);

let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_one::<usize>("flag").copied(),
    Some(5)
);
§

SetFalse

When encountered, act as if "false" was encountered on the command-line

If no default_value is set, it will be true.

No value is allowed. To optionally accept a value, see Arg::default_missing_value

NOTE: If the argument has previously been seen, it will result in a ArgumentConflict unless Command::args_override_self(true) is set.

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .action(clap::ArgAction::SetFalse)
    );

let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_flag("flag"),
    false
);

let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_flag("flag"),
    true
);
§

Count

When encountered, increment a u8 counter starting from 0.

If no default_value is set, it will be 0.

No value is allowed. To optionally accept a value, see Arg::default_missing_value

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("flag")
            .long("flag")
            .action(clap::ArgAction::Count)
    );

let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_count("flag"),
    2
);

let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(
    matches.get_count("flag"),
    0
);
§

Help

When encountered, display Command::print_help

Depending on the flag, Command::print_long_help may be shown

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("special-help")
            .short('?')
            .action(clap::ArgAction::Help)
    );

// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);

// New help available
let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
§

HelpShort

When encountered, display Command::print_help

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("special-help")
            .short('?')
            .action(clap::ArgAction::HelpShort)
    );

// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);

// New help available
let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
§

HelpLong

When encountered, display Command::print_long_help

§Examples

let cmd = Command::new("mycmd")
    .arg(
        Arg::new("special-help")
            .short('?')
            .action(clap::ArgAction::HelpLong)
    );

// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);

// New help available
let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
§

Version

When encountered, display Command::version

Depending on the flag, Command::long_version may be shown

§Examples

let cmd = Command::new("mycmd")
    .version("1.0.0")
    .arg(
        Arg::new("special-version")
            .long("special-version")
            .action(clap::ArgAction::Version)
    );

// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "--version"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayVersion);

// New help available
let err = cmd.try_get_matches_from(["mycmd", "--special-version"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayVersion);

Implementations§

Source§

impl ArgAction

Source

pub fn takes_values(&self) -> bool

Returns whether this action accepts values on the command-line

default_values and [env][super::Arg::env] may still be processed.

Trait Implementations§

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impl Clone for ArgAction

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fn clone(&self) -> ArgAction

Returns a copy of the value. Read more
1.0.0 · Source§

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

Performs copy-assignment from source. Read more
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impl Debug for ArgAction

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

Formats the value using the given formatter. Read more
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impl IntoResettable<ArgAction> for ArgAction

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fn into_resettable(self) -> Resettable<ArgAction>

Convert to the intended resettable type
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impl IntoResettable<ArgAction> for Option<ArgAction>

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fn into_resettable(self) -> Resettable<ArgAction>

Convert to the intended resettable type

Auto Trait Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dst: *mut u8)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 1 byte

Size for each variant:

  • Set: 0 bytes
  • Append: 0 bytes
  • SetTrue: 0 bytes
  • SetFalse: 0 bytes
  • Count: 0 bytes
  • Help: 0 bytes
  • HelpShort: 0 bytes
  • HelpLong: 0 bytes
  • Version: 0 bytes