Specifying argument types

There are three types of arguments that can be supplied to each (sub-)command:

• short (e.g. -h),
• long (e.g. --help)
• and positional.

Like clap, structopt defaults to creating positional arguments.

If you want to generate a long argument you can specify either long = $NAME, or just long to get a long flag generated using the field name. The generated casing style can be modified using the rename_all attribute. See the rename_all example for more.

For short arguments, short will use the first letter of the field name by default, but just like the long option it's also possible to use a custom letter through short = $LETTER.

If an argument is renamed using name = $NAME any following call to short or long will use the new name.

Attention: If these arguments are used without an explicit name the resulting flag is going to be renamed using kebab-case if the rename_all attribute was not specified previously. The same is true for subcommands with implicit naming through the related data structure.

use structopt::StructOpt;

#[derive(StructOpt)]
#[structopt(rename_all = "kebab-case")]
struct Opt {
    /// This option can be specified with something like `--foo-option
    /// value` or `--foo-option=value`
    #[structopt(long)]
    foo_option: String,

    /// This option can be specified with something like `-b value` (but
    /// not `--bar-option value`).
    #[structopt(short)]
    bar_option: String,

    /// This option can be specified either `--baz value` or `-z value`.
    #[structopt(short = "z", long = "baz")]
    baz_option: String,

    /// This option can be specified either by `--custom value` or
    /// `-c value`.
    #[structopt(name = "custom", long, short)]
    custom_option: String,

    /// This option is positional, meaning it is the first unadorned string
    /// you provide (multiple others could follow).
    my_positional: String,

    /// This option is skipped and will be filled with the default value
    /// for its type (in this case 0).
    #[structopt(skip)]
    skipped: u32,

}

# fn main() {
# Opt::from_clap(&Opt::clap().get_matches_from(
#    &["test", "--foo-option", "", "-b", "", "--baz", "", "--custom", "", "positional"]));
# }