Function number_range 

pub fn number_range<T>(s: &str, min: T, max: T) -> Result<T, String>
where
    T: FromStr + Ord + PartialOrd + Display,
    <T as FromStr>::Err: Display,

Validate a signed or unsigned integer value.

Arguments

• s - String to parse.
• min - Minimum value, inclusive.
• max - Maximum value, inclusive.

Example

This allows for a number of cents to be passed in the range of 0-99 (inclusive).

use clap::Parser;
use clap_num::number_range;

fn less_than_100(s: &str) -> Result<u8, String> {
    number_range(s, 0, 99)
}

#[derive(Parser)]
struct Change {
    #[clap(long, value_parser=less_than_100)]
    cents: u8,
}

To run this example run cargo run --example change, giving arguments to the program after --, for example:

$ cargo run --example change -- --cents 99
Change: 99 cents

Error Messages

Values that are not numbers will show an error message similar to this:

error: Invalid value for '--cents <cents>': invalid digit found in string

Values resulting in integer overflow will show an error message similar to this:

error: Invalid value for '--cents <cents>': number too large to fit in target type

Values exceeding the limits will show an error message similar to this:

error: Invalid value for '--cents <cents>': exceeds maximum of 99