Module clap::_derive::_cookbook::pacman

Available on crate feature unstable-doc only.

Example: pacman-like CLI (Builder API)

use clap::{Arg, ArgAction, Command};

fn main() {
    let matches = Command::new("pacman")
        .about("package manager utility")
        .version("5.2.1")
        .subcommand_required(true)
        .arg_required_else_help(true)
        .author("Pacman Development Team")
        // Query subcommand
        //
        // Only a few of its arguments are implemented below.
        .subcommand(
            Command::new("query")
                .short_flag('Q')
                .long_flag("query")
                .about("Query the package database.")
                .arg(
                    Arg::new("search")
                        .short('s')
                        .long("search")
                        .help("search locally installed packages for matching strings")
                        .conflicts_with("info")
                        .takes_value(true)
                        .multiple_values(true),
                )
                .arg(
                    Arg::new("info")
                        .long("info")
                        .short('i')
                        .conflicts_with("search")
                        .help("view package information")
                        .takes_value(true)
                        .multiple_values(true),
                ),
        )
        // Sync subcommand
        //
        // Only a few of its arguments are implemented below.
        .subcommand(
            Command::new("sync")
                .short_flag('S')
                .long_flag("sync")
                .about("Synchronize packages.")
                .arg(
                    Arg::new("search")
                        .short('s')
                        .long("search")
                        .conflicts_with("info")
                        .takes_value(true)
                        .multiple_values(true)
                        .help("search remote repositories for matching strings"),
                )
                .arg(
                    Arg::new("info")
                        .long("info")
                        .conflicts_with("search")
                        .short('i')
                        .action(ArgAction::SetTrue)
                        .help("view package information"),
                )
                .arg(
                    Arg::new("package")
                        .help("packages")
                        .required_unless_present("search")
                        .takes_value(true)
                        .multiple_values(true),
                ),
        )
        .get_matches();

    match matches.subcommand() {
        Some(("sync", sync_matches)) => {
            if sync_matches.contains_id("search") {
                let packages: Vec<_> = sync_matches
                    .get_many::<String>("search")
                    .expect("contains_id")
                    .map(|s| s.as_str())
                    .collect();
                let values = packages.join(", ");
                println!("Searching for {}...", values);
                return;
            }

            let packages: Vec<_> = sync_matches
                .get_many::<String>("package")
                .expect("is present")
                .map(|s| s.as_str())
                .collect();
            let values = packages.join(", ");

            if sync_matches.get_flag("info") {
                println!("Retrieving info for {}...", values);
            } else {
                println!("Installing {}...", values);
            }
        }
        Some(("query", query_matches)) => {
            if let Some(packages) = query_matches.get_many::<String>("info") {
                let comma_sep = packages.map(|s| s.as_str()).collect::<Vec<_>>().join(", ");
                println!("Retrieving info for {}...", comma_sep);
            } else if let Some(queries) = query_matches.get_many::<String>("search") {
                let comma_sep = queries.map(|s| s.as_str()).collect::<Vec<_>>().join(", ");
                println!("Searching Locally for {}...", comma_sep);
            } else {
                println!("Displaying all locally installed packages...");
            }
        }
        _ => unreachable!(), // If all subcommands are defined above, anything else is unreachable
    }
}

pacman defines subcommands via flags.

Here, -S is a short flag subcommand:

$ pacman -S package
Installing package...

Here --sync is a long flag subcommand:

$ pacman --sync package
Installing package...

Now the short flag subcommand (-S) with a long flag:

$ pacman -S --search name
Searching for name...

And the various forms of short flags that work:

$ pacman -S -s name
Searching for name...

$ pacman -Ss name
Searching for name...

(users can “stack” short subcommands with short flags or with other short flag subcommands)

In the help, this looks like:

$ pacman -h
pacman 5.2.1
Pacman Development Team
package manager utility

USAGE:
    pacman[EXE] <SUBCOMMAND>

OPTIONS:
    -h, --help       Print help information
    -V, --version    Print version information

SUBCOMMANDS:
    help                Print this message or the help of the given subcommand(s)
    query -Q --query    Query the package database.
    sync -S --sync      Synchronize packages.

$ pacman -S -h
pacman[EXE]-sync 
Synchronize packages.

USAGE:
    pacman[EXE] {sync|--sync|-S} [OPTIONS] [--] [package]...

ARGS:
    <package>...    packages

OPTIONS:
    -h, --help                  Print help information
    -i, --info                  view package information
    -s, --search <search>...    search remote repositories for matching strings

And errors:

$ pacman -S -s foo -i bar
? failed
error: The argument '--search <search>...' cannot be used with '--info'

USAGE:
    pacman[EXE] {sync|--sync|-S} --search <search>... <package>...

For more information try --help

NOTE: Keep in mind that subcommands, flags, and long flags are case sensitive: -Q and -q are different flags/subcommands. For example, you can have both -Q subcommand and -q flag, and they will be properly disambiguated. Let’s make a quick program to illustrate.