Struct clap::App

pub struct App<'a, 'b> where 'a: 'b {
    // some fields omitted
}

Used to create a representation of a command line program and all possible command line arguments. Application settings are set using the "builder pattern" with the .get_matches() family of methods being the terminal methods that starts the runtime-parsing process. These methods then return information about the user supplied arguments (or lack there of).

NOTE: There aren't any mandatory "options" that one must set. The "options" may also appear in any order (so long as one of the App::get_matches* methods is the last method called).

Examples

let m = App::new("My Program")
    .author("Me, me@mail.com")
    .version("1.0.2")
    .about("Explains in brief what the program does")
    .arg(
        Arg::with_name("in_file").index(1)
    )
    .after_help("Longer explaination to appear after the options when \
                 displaying the help information from --help or -h")
    .get_matches();

// Your program logic starts here...

Methods

impl<'a, 'b> App<'a, 'b>

fn new<S: Into<String>>(n: S) -> Self

Creates a new instance of an application requiring a name. The name may be, but doesn't have to be same as the binary. The name will be displayed to the user when they request to print version or help and usage information.

Examples

let prog = App::new("My Program")

fn author<S: Into<&'b str>>(self, author: S) -> Self

Sets a string of author(s) that will be displayed to the user when they request the help information with --help or -h.

Pro-tip: If you turn on unstable features you can use claps convienience macro crate_authors! to automatically set your application's author to the same thing as your crate at compile time. See the examples/ directory for more information

Examples

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

fn bin_name<S: Into<String>>(self, name: S) -> Self

Overrides the system-determined binary name. This should only be used when absolutely neccessary, 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 command should not be used for SubCommands.

Examples

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

fn about<S: Into<&'b str>>(self, about: S) -> Self

Sets a string describing what the program does. This will be displayed when displaying help information.

Examples

App::new("myprog")
    .about("Does really amazing things to great people")

fn after_help<S: Into<&'b str>>(self, help: S) -> Self

Adds additional help information to be displayed in addition to auto-generated help. This information is displayed after the auto-generated help information. This is often used to describe how to use the arguments, or caveats to be noted.

Examples

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

fn before_help<S: Into<&'b str>>(self, help: S) -> Self

Adds additional help information to be displayed in addition to auto-generated help. This information is displayed before the auto-generated help information. This is often used for header information.

Examples

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

fn version<S: Into<&'b str>>(self, ver: S) -> Self

Sets a string of the version number to be displayed when displaying version or help information.

Pro-tip: Use claps convienience macro crate_version! to automatically set your application's version to the same thing as your crate at compile time. See the examples/ directory for more information

Examples

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

fn usage<S: Into<&'b str>>(self, usage: S) -> Self

Sets a custom usage string to override the auto-generated usage string.

This will be displayed to the user when errors are found in argument parsing, or when you call ArgMatches::usage

CAUTION: 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: You do not need to specify the "USAGE: \n\t" portion, as that will still be applied by clap, you only need to specify the portion starting with the binary name.

NOTE: This will not replace the entire help message, only the portion showing the usage.

Examples

App::new("myprog")
    .usage("myapp [-clDas] <some_file>")

fn help<S: Into<&'b str>>(self, help: S) -> Self

Sets a custom help message and overrides the auto-generated one. This should only be used when the auto-generated message does not suffice.

This will be displayed to the user when they use --help or -h

NOTE: This replaces the entire help message, so nothing will be auto-generated.

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 .help() for them as well.

Examples

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

           USAGE: myapp <opts> <comamnd>\n\n\

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

           Commmands:\n\
           help             Prints this message\n\
           work             Do some work")

fn help_short<S: AsRef<str> + 'b>(self, s: S) -> Self

Sets the short version of the help argument without the preceding -.

By default clap automatically assigns h, but this can be overridden by defining your own argument with a lowercase h as the short. clap lazily generates these help arguments after you've defined any arguments of your own.

NOTE: Any leading - characters will be stripped, and only the first non - chacter will be used as the short version

Examples

App::new("myprog")
    .help_short("H") // Using an uppercase `H` instead of the default lowercase `h`

fn version_short<S: AsRef<str>>(self, s: S) -> Self

Sets the short version of the version argument without the preceding -.

By default clap automatically assigns V, but this can be overridden by defining your own argument with a uppercase V as the short. clap lazily generates these version arguments after you've defined any arguments of your own.

NOTE: Any leading - characters will be stripped, and only the first non - chacter will be used as the short version

Examples

App::new("myprog")
    .version_short("v") // Using a lowercase `v` instead of the default capital `V`

fn template<S: Into<&'b str>>(self, s: S) -> Self

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

Tags arg given inside curly brackets: Valid tags are: * {bin} - Binary name. * {version} - Version number. * {author} - Author information. * {usage} - Automatically generated or given usage string. * {all-args} - Help for all arguments (options, flags, positionals arguments, and subcommands) including titles. * {unified} - Unified help for options and flags. * {flags} - Help for flags. * {options} - Help for options. * {positionals} - Help for positionals arguments. * {subcommands} - Help for subcommands. * {after-help} - Help for flags.

Examples

App::new("myprog")
    .version("1.0")
    .template("{bin} ({version}) - {usage}")

NOTE:The template system is, on purpose, very simple. Therefore the tags have to writen in the lowercase and without spacing.

fn setting(self, setting: AppSettings) -> Self

Enables a single Application level settings.

See AppSettings for a full list of possibilities and examples.

Examples

App::new("myprog")
    .setting(AppSettings::SubcommandRequired)
    .setting(AppSettings::WaitOnError)

fn settings(self, settings: &[AppSettings]) -> Self

Enables multiple Application level settings

See AppSettings for a full list of possibilities and examples.

Examples

App::new("myprog")
    .settings(&[AppSettings::SubcommandRequired,
                 AppSettings::WaitOnError])

fn arg<A: Borrow<Arg<'a, 'b>> + 'a>(self, a: A) -> Self

Adds an argument to the list of valid possibilties.

Examples

App::new("myprog")
    // Adding a single "flag" argument with a short and help text, using Arg::with_name()
    .arg(
        Arg::with_name("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_usage()
    .arg(
        Arg::from_usage("-c --config=[CONFIG] 'Optionally sets a config file to use'")
    )

fn args(self, args: &[Arg<'a, 'b>]) -> Self

Adds multiple arguments to the list of valid possibilties

Examples

App::new("myprog")
    .args(
        &[Arg::from_usage("[debug] -d 'turns on debugging info'"),
         Arg::with_name("input").index(1).help("the input file to use")]
    )

fn arg_from_usage(self, usage: &'a str) -> Self

A convienience method for adding a single argument from a usage type string. The string used follows the same rules and syntax as Arg::from_usage()

NOTE: The downside to using this method is that you can not set any additional properties of the Arg other than what Arg::from_usage() supports.

Examples

App::new("myprog")
    .arg_from_usage("-c --config=<FILE> 'Sets a configuration file to use'")

fn args_from_usage(self, usage: &'a str) -> Self

Adds multiple arguments at once from a usage string, one per line. See Arg::from_usage() for details on the syntax and rules supported.

NOTE: Like App::arg_from_usage() the downside is you only set properties for the Args which Arg::from_usage() supports.

Examples

App::new("myprog")
    .args_from_usage(
        "-c --config=[FILE] 'Sets a configuration file to use'
         [debug]... -d 'Sets the debugging level'
         <FILE> 'The input file to use'"
    )

fn group(self, group: ArgGroup<'a>) -> Self

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. For instance, you can make an entire ArgGroup required, meaning that one (and only one) argument from that group must be present at runtime.

You can also do things such as 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.

Another added benfit of ArgGroups is that you can extract a value from a group instead of determining exactly which argument was used.

Finally, using ArgGroups to ensure exclusion between arguments is another very common use

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.

App::new("app")
    .args_from_usage(
        "--set-ver [ver] 'set the version manually'
         --major         'auto increase major'
         --minor         'auto increase minor'
         --patch         'auto increase patch'")
    .group(ArgGroup::with_name("vers")
         .args(&["set-ver", "major", "minor","patch"])
         .required(true))

fn groups(self, groups: &[ArgGroup<'a>]) -> Self

Adds multiple ArgGroups to the application at once.

Examples

App::new("app")
    .args_from_usage(
        "--set-ver [ver] 'set the version manually'
         --major         'auto increase major'
         --minor         'auto increase minor'
         --patch         'auto increase patch'
         -c [FILE]       'a config file'
         -i [IFACE]      'an interface'")
    .groups(&[
        ArgGroup::with_name("vers")
            .args(&["set-ver", "major", "minor","patch"])
            .required(true),
        ArgGroup::with_name("input")
            .args(&["c", "i"])
    ])

fn subcommand(self, subcmd: App<'a, 'b>) -> Self

Adds a subcommand to the list of valid possibilties. Subcommands are effectively sub-apps, because they can contain their own arguments, subcommands, version, usage, etc. They also function just like apps, in that they get their own auto generated help, version, and usage.

Examples

App::new("myprog")
    .subcommand(SubCommand::with_name("config")
        .about("Controls configuration features")
        .arg_from_usage("<config> 'Required configuration file to use'"))

fn subcommands<I>(self, subcmds: I) -> Self where I: IntoIterator<Item=App<'a, 'b>>

Adds multiple subcommands to the list of valid possibilties by iterating over a Vec of SubCommands

Examples

.subcommands( vec![
       SubCommand::with_name("config").about("Controls configuration functionality")
                                .arg(Arg::with_name("config_file").index(1)),
       SubCommand::with_name("debug").about("Controls debug functionality")])

fn display_order(self, ord: usize) -> Self

Allows custom ordering of subcommands within the help message. Subcommands with a lower value will be displayed first in the help message. This is helpful when one would like to emphasise frequently used subcommands, or prioritize those towards the top of the list. Duplicate values are allowed. Subcommands with duplicate display orders will be displayed in alphabetical order.

NOTE: The default is 999 for all subcommands.

Examples

let m = App::new("cust-ord")
    .subcommand(SubCommand::with_name("alpha") // typically subcommands are grouped
                                               // alphabetically by name. Subcommands
                                               // without a display_order have a value of
                                               // 999 and are displayed alphabetically with
                                               // all other 999 subcommands
        .about("Some help and text"))
    .subcommand(SubCommand::with_name("beta")
        .display_order(1)   // In order to force this subcommand to appear *first*
                            // all we have to do is give it a value lower than 999.
                            // Any other subcommands with a value of 1 will be displayed
                            // alphabetically with this one...then 2 values, then 3, etc.
        .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 [FLAGS] [OPTIONS]

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

SUBCOMMANDS:
    beta    I should be first!
    alpha   Some help and text

fn print_help(&self) -> ClapResult<()>

Prints the full help message to io::stdout() using a BufWriter

Examples

let app = App::new("myprog");
app.print_help();

fn write_help<W: Write>(&self, w: &mut W) -> ClapResult<()>

Writes the full help message to the user to a io::Write object

Examples

use std::io;
let mut app = App::new("myprog");
let mut out = io::stdout();
app.write_help(&mut out).ok().expect("failed to write to stdout");

fn get_matches(self) -> ArgMatches<'a>

Starts the parsing process, upon a failed parse an error will be displayed to the user and the process with exit with the appropriate error code. By default this method gets matches from env::args_os

Examples

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

fn get_matches_safe(self) -> ClapResult<ArgMatches<'a>>

Starts the parsing process. This method will return a Result type instead of exiting the the process on failed parse. By default this method gets matches from env::args_os

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

Examples

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

fn get_matches_from<I, T>(self, itr: I) -> ArgMatches<'a> where I: IntoIterator<Item=T>, T: Into<OsString>

Starts the parsing process. Like App::get_matches this method does not return a Result and will automatically exit with an error message. This method, however, lets you specify what iterator to use when performing matches, such as a Vec of your making.

NOTE: The first argument will be parsed as the binary name unless AppSettings::NoBinaryName is used

Examples

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

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

fn get_matches_from_safe<I, T>(self, itr: I) -> ClapResult<ArgMatches<'a>> where I: IntoIterator<Item=T>, T: Into<OsString>

Starts the parsing process. A combination of App::get_matches_from, and App::get_matches_safe

NOTE: This method WILL NOT exit when --help or --version (or short versions) are used. It will return an error, where the kind is a ErrorKind::HelpDisplayed or ErrorKind::VersionDisplayed 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 AppSettings::NoBinaryName is used

Examples

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

let matches = App::new("myprog")
    // Args and options go here...
    .get_matches_from_safe(arg_vec)
    .unwrap_or_else( |e| { panic!("An error occurs: {}", e) });

fn get_matches_from_safe_borrow<I, T>(&mut self, itr: I) -> ClapResult<ArgMatches<'a>> where I: IntoIterator<Item=T>, T: Into<OsString>

Starts the parsing process without consuming the App struct self. This is normally not the desired functionality, instead prefer App::get_matches_from_safe which does consume self.

NOTE: The first argument will be parsed as the binary name unless AppSettings::NoBinaryName is used

Examples

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

let mut app = App::new("myprog");
    // Args and options go here...
let matches = app.get_matches_from_safe_borrow(arg_vec)
    .unwrap_or_else( |e| { panic!("An error occurs: {}", e) });

Trait Implementations

impl<'a, 'b> Clone for App<'a, 'b>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'n, 'e> Display for App<'n, 'e>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.