Enum clap::AppSettings

#[non_exhaustive]
pub enum AppSettings {
    IgnoreErrors,
    WaitOnError,
    AllowHyphenValues,
    AllowNegativeNumbers,
    AllArgsOverrideSelf,
    AllowMissingPositional,
    TrailingVarArg,
    DontDelimitTrailingValues,
    InferLongArgs,
    InferSubcommands,
    SubcommandRequired,
    SubcommandRequiredElseHelp,
    AllowExternalSubcommands,
    AllowInvalidUtf8ForExternalSubcommands,
    UseLongFormatForHelpSubcommand,
    SubcommandsNegateReqs,
    ArgsNegateSubcommands,
    SubcommandPrecedenceOverArg,
    ArgRequiredElseHelp,
    DeriveDisplayOrder,
    DontCollapseArgsInUsage,
    NextLineHelp,
    DisableColoredHelp,
    DisableHelpFlag,
    DisableHelpSubcommand,
    DisableVersionFlag,
    PropagateVersion,
    Hidden,
    HidePossibleValues,
    HelpExpected,
    NoBinaryName,
    NoAutoHelp,
    NoAutoVersion,
    AllowLeadingHyphen,
    StrictUtf8,
    UnifiedHelpMessage,
    ColoredHelp,
    ColorAuto,
    ColorAlways,
    ColorNever,
    DisableHelpFlags,
    DisableVersion,
    GlobalVersion,
    HidePossibleValuesInHelp,
    UnifiedHelp,
    // some variants omitted
}

Application level settings, which affect how App operates

NOTE: When these settings are used, they apply only to current command, and are not propagated down or up through child or parent subcommands

Variants (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.

IgnoreErrors

Try not to fail on parse errors, like missing option values.

Note: Make sure you apply it as global_setting if you want this setting to be propagated to subcommands and sub-subcommands!

let app = App::new("app")
  .global_setting(AppSettings::IgnoreErrors)
  .arg(arg!(-c --config <FILE> "Sets a custom config file").required(false))
  .arg(arg!(-x --stuff <FILE> "Sets a custom stuff file").required(false))
  .arg(arg!(f: -f "Flag"));

let r = app.try_get_matches_from(vec!["app", "-c", "file", "-f", "-x"]);

assert!(r.is_ok(), "unexpected error: {:?}", r);
let m = r.unwrap();
assert_eq!(m.value_of("config"), Some("file"));
assert!(m.is_present("f"));
assert_eq!(m.value_of("stuff"), None);

WaitOnError

Display the message “Press [ENTER]/[RETURN] to continue…” and wait for user before exiting

This is most useful when writing an application which is run from a GUI shortcut, or on Windows where a user tries to open the binary by double-clicking instead of using the command line.

Examples

App::new("myprog")
    .global_setting(AppSettings::WaitOnError);

AllowHyphenValues

Specifies that leading hyphens are allowed in all argument values (e.g. -10).

Otherwise they will be parsed as another flag or option. See also AppSettings::AllowNegativeNumbers.

NOTE: Use this setting with caution as it silences certain circumstances which would otherwise be an error (such as accidentally forgetting to specify a value for leading option). It is preferred to set this on a per argument basis, via Arg::allow_hyphen_values.

Examples

// Imagine you needed to represent negative numbers as well, such as -10
let m = App::new("nums")
    .setting(AppSettings::AllowHyphenValues)
    .arg(Arg::new("neg"))
    .get_matches_from(vec![
        "nums", "-20"
    ]);

assert_eq!(m.value_of("neg"), Some("-20"));

AllowNegativeNumbers

Allows negative numbers to pass as values.

This is similar to AppSettings::AllowHyphenValues except that it only allows numbers, all other undefined leading hyphens will fail to parse.

Examples

let res = App::new("myprog")
    .global_setting(AppSettings::AllowNegativeNumbers)
    .arg(Arg::new("num"))
    .try_get_matches_from(vec![
        "myprog", "-20"
    ]);
assert!(res.is_ok());
let m = res.unwrap();
assert_eq!(m.value_of("num").unwrap(), "-20");

AllArgsOverrideSelf

Specifies that all arguments override themselves.

This is the equivalent to saying the foo arg using Arg::overrides_with("foo") for all defined arguments.

AllowMissingPositional

Allows one to implement two styles of CLIs where positionals can be used out of order.

The first example is a CLI where the second to last positional argument is optional, but the final positional argument is required. Such as $ prog [optional] <required> where one of the two following usages is allowed:

• $ prog [optional] <required>
• $ prog <required>

This would otherwise not be allowed. This is useful when [optional] has a default value.

Note: when using this style of “missing positionals” the final positional must be required if -- will not be used to skip to the final positional argument.

Note: This style also only allows a single positional argument to be “skipped” without the use of --. To skip more than one, see the second example.

The second example is when one wants to skip multiple optional positional arguments, and use of the -- operator is OK (but not required if all arguments will be specified anyways).

For example, imagine a CLI which has three positional arguments [foo] [bar] [baz]... where baz accepts multiple values (similar to man ARGS... style training arguments).

With this setting the following invocations are posisble:

• $ prog foo bar baz1 baz2 baz3
• $ prog foo -- baz1 baz2 baz3
• $ prog -- baz1 baz2 baz3

Examples

Style number one from above:

// Assume there is an external subcommand named "subcmd"
let m = App::new("myprog")
    .setting(AppSettings::AllowMissingPositional)
    .arg(Arg::new("arg1"))
    .arg(Arg::new("arg2")
        .required(true))
    .get_matches_from(vec![
        "prog", "other"
    ]);

assert_eq!(m.value_of("arg1"), None);
assert_eq!(m.value_of("arg2"), Some("other"));

Now the same example, but using a default value for the first optional positional argument

// Assume there is an external subcommand named "subcmd"
let m = App::new("myprog")
    .setting(AppSettings::AllowMissingPositional)
    .arg(Arg::new("arg1")
        .default_value("something"))
    .arg(Arg::new("arg2")
        .required(true))
    .get_matches_from(vec![
        "prog", "other"
    ]);

assert_eq!(m.value_of("arg1"), Some("something"));
assert_eq!(m.value_of("arg2"), Some("other"));

Style number two from above:

// Assume there is an external subcommand named "subcmd"
let m = App::new("myprog")
    .setting(AppSettings::AllowMissingPositional)
    .arg(Arg::new("foo"))
    .arg(Arg::new("bar"))
    .arg(Arg::new("baz").takes_value(true).multiple_values(true))
    .get_matches_from(vec![
        "prog", "foo", "bar", "baz1", "baz2", "baz3"
    ]);

assert_eq!(m.value_of("foo"), Some("foo"));
assert_eq!(m.value_of("bar"), Some("bar"));
assert_eq!(m.values_of("baz").unwrap().collect::<Vec<_>>(), &["baz1", "baz2", "baz3"]);

Now nofice if we don’t specify foo or baz but use the -- operator.

// Assume there is an external subcommand named "subcmd"
let m = App::new("myprog")
    .setting(AppSettings::AllowMissingPositional)
    .arg(Arg::new("foo"))
    .arg(Arg::new("bar"))
    .arg(Arg::new("baz").takes_value(true).multiple_values(true))
    .get_matches_from(vec![
        "prog", "--", "baz1", "baz2", "baz3"
    ]);

assert_eq!(m.value_of("foo"), None);
assert_eq!(m.value_of("bar"), None);
assert_eq!(m.values_of("baz").unwrap().collect::<Vec<_>>(), &["baz1", "baz2", "baz3"]);

TrailingVarArg

Specifies that the final positional argument is a “VarArg” and that clap should not attempt to parse any further args.

The values of the trailing positional argument will contain all args from itself on.

NOTE: The final positional argument must have Arg::multiple_values(true) or the usage string equivalent.

Examples

let m = App::new("myprog")
    .setting(AppSettings::TrailingVarArg)
    .arg(arg!(<cmd> ... "commands to run"))
    .get_matches_from(vec!["myprog", "arg1", "-r", "val1"]);

let trail: Vec<&str> = m.values_of("cmd").unwrap().collect();
assert_eq!(trail, ["arg1", "-r", "val1"]);

DontDelimitTrailingValues

Disables the automatic delimiting of values when -- or AppSettings::TrailingVarArg was used.

NOTE: The same thing can be done manually by setting the final positional argument to Arg::use_delimiter(false). Using this setting is safer, because it’s easier to locate when making changes.

Examples

App::new("myprog")
    .setting(AppSettings::DontDelimitTrailingValues)
    .get_matches();

InferLongArgs

Allow partial matches of long arguments or their aliases.

For example, to match an argument named --test, one could use --t, --te, --tes, and --test.

NOTE: The match must not be ambiguous at all in order to succeed. i.e. to match --te to --test there could not also be another argument or alias --temp because both start with --te

InferSubcommands

Allow partial matches of subcommand names and their aliases.

For example, to match a subcommand named test, one could use t, te, tes, and test.

NOTE: The match must not be ambiguous at all in order to succeed. i.e. to match te to test there could not also be a subcommand or alias temp because both start with te

CAUTION: This setting can interfere with positional/free arguments, take care when designing CLIs which allow inferred subcommands and have potential positional/free arguments whose values could start with the same characters as subcommands. If this is the case, it’s recommended to use settings such as AppSettings::ArgsNegateSubcommands in conjunction with this setting.

Examples

let m = App::new("prog")
    .global_setting(AppSettings::InferSubcommands)
    .subcommand(App::new("test"))
    .get_matches_from(vec![
        "prog", "te"
    ]);
assert_eq!(m.subcommand_name(), Some("test"));

SubcommandRequired

If no subcommand is present at runtime, error and exit gracefully.

Examples

let err = App::new("myprog")
    .setting(AppSettings::SubcommandRequired)
    .subcommand(App::new("test"))
    .try_get_matches_from(vec![
        "myprog",
    ]);
assert!(err.is_err());
assert_eq!(err.unwrap_err().kind, ErrorKind::MissingSubcommand);

SubcommandRequiredElseHelp

Display help if no subcommands are present at runtime and exit gracefully (i.e. an empty run such as $ myprog).

NOTE: This should not be used with AppSettings::SubcommandRequired as they do nearly same thing; this prints the help text, and the other prints an error.

NOTE: If the user specifies arguments at runtime, but no subcommand the help text will still be displayed and exit. If this is not the desired result, consider using AppSettings::ArgRequiredElseHelp instead.

Examples

App::new("myprog")
    .setting(AppSettings::SubcommandRequiredElseHelp);

AllowExternalSubcommands

Assume unexpected positional arguments are a subcommand.

NOTE: Use this setting with caution, as a truly unexpected argument (i.e. one that is NOT an external subcommand) will not cause an error and instead be treated as a potential subcommand. One should check for such cases manually and inform the user appropriately.

Examples

// Assume there is an external subcommand named "subcmd"
let m = App::new("myprog")
    .setting(AppSettings::AllowExternalSubcommands)
    .get_matches_from(vec![
        "myprog", "subcmd", "--option", "value", "-fff", "--flag"
    ]);

// All trailing arguments will be stored under the subcommand's sub-matches using an empty
// string argument name
match m.subcommand() {
    Some((external, ext_m)) => {
         let ext_args: Vec<&str> = ext_m.values_of("").unwrap().collect();
         assert_eq!(external, "subcmd");
         assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    },
    _ => {},
}

AllowInvalidUtf8ForExternalSubcommands

Specifies that external subcommands that are invalid UTF-8 should not be treated as an error.

NOTE: Using external subcommand argument values with invalid UTF-8 requires using ArgMatches::values_of_os or ArgMatches::values_of_lossy for those particular arguments which may contain invalid UTF-8 values

NOTE: Setting this requires AppSettings::AllowExternalSubcommands

Platform Specific

Non Windows systems only

Examples

// Assume there is an external subcommand named "subcmd"
let m = App::new("myprog")
   .setting(AppSettings::AllowInvalidUtf8ForExternalSubcommands)
   .setting(AppSettings::AllowExternalSubcommands)
   .get_matches_from(vec![
       "myprog", "subcmd", "--option", "value", "-fff", "--flag"
   ]);

// All trailing arguments will be stored under the subcommand's sub-matches using an empty
// string argument name
match m.subcommand() {
   Some((external, ext_m)) => {
        let ext_args: Vec<&std::ffi::OsStr> = ext_m.values_of_os("").unwrap().collect();
        assert_eq!(external, "subcmd");
        assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
   },
   _ => {},
}

UseLongFormatForHelpSubcommand

Specifies that the help subcommand should print the long help message (--help).

NOTE: This setting is useless if AppSettings::DisableHelpSubcommand or AppSettings::NoAutoHelp is set, or if the app contains no subcommands at all.

Examples

App::new("myprog")
    .global_setting(AppSettings::UseLongFormatForHelpSubcommand)
    .subcommand(App::new("test")
        .arg(Arg::new("foo")
            .help("short form about message")
            .long_help("long form about message")
        )
    )
    .get_matches();

SubcommandsNegateReqs

Allows subcommands to override all requirements of the parent command.

For example, if you had a subcommand or top level application with a required argument that is only required as long as there is no subcommand present, using this setting would allow you to set those arguments to Arg::required(true) and yet receive no error so long as the user uses a valid subcommand instead.

NOTE: This defaults to false (using subcommand does not negate requirements)

Examples

This first example shows that it is an error to not use a required argument

let err = App::new("myprog")
    .setting(AppSettings::SubcommandsNegateReqs)
    .arg(Arg::new("opt").required(true))
    .subcommand(App::new("test"))
    .try_get_matches_from(vec![
        "myprog"
    ]);
assert!(err.is_err());
assert_eq!(err.unwrap_err().kind, ErrorKind::MissingRequiredArgument);

This next example shows that it is no longer error to not use a required argument if a valid subcommand is used.

let noerr = App::new("myprog")
    .setting(AppSettings::SubcommandsNegateReqs)
    .arg(Arg::new("opt").required(true))
    .subcommand(App::new("test"))
    .try_get_matches_from(vec![
        "myprog", "test"
    ]);
assert!(noerr.is_ok());

ArgsNegateSubcommands

Specifies that use of an argument prevents the use of subcommands.

By default clap allows arguments between subcommands such as <cmd> [cmd_args] <subcmd> [subcmd_args] <subsubcmd> [subsubcmd_args].

This setting disables that functionality and says that arguments can only follow the final subcommand. For instance using this setting makes only the following invocations possible:

• <cmd> <subcmd> <subsubcmd> [subsubcmd_args]
• <cmd> <subcmd> [subcmd_args]
• <cmd> [cmd_args]

Examples

App::new("myprog")
    .setting(AppSettings::ArgsNegateSubcommands);

SubcommandPrecedenceOverArg

Prevent subcommands from being consumed as an arguments value.

By default, if an option taking multiple values is followed by a subcommand, the subcommand will be parsed as another value.

app --foo val1 val2 subcommand
          --------- ----------
            values   another value

This setting instructs the parser to stop when encountering a subcommand instead of greedily consuming arguments.

app --foo val1 val2 subcommand
          --------- ----------
            values   subcommand

Note: Make sure you apply it as global_setting if you want this setting to be propagated to subcommands and sub-subcommands!

Examples

let app = App::new("app").subcommand(App::new("sub")).arg(
    Arg::new("arg")
        .long("arg")
        .multiple_values(true)
        .takes_value(true),
);

let matches = app
    .clone()
    .try_get_matches_from(&["app", "--arg", "1", "2", "3", "sub"])
    .unwrap();

assert_eq!(
    matches.values_of("arg").unwrap().collect::<Vec<_>>(),
    &["1", "2", "3", "sub"]
);
assert!(matches.subcommand_matches("sub").is_none());

let matches = app
    .setting(AppSettings::SubcommandPrecedenceOverArg)
    .try_get_matches_from(&["app", "--arg", "1", "2", "3", "sub"])
    .unwrap();

assert_eq!(
    matches.values_of("arg").unwrap().collect::<Vec<_>>(),
    &["1", "2", "3"]
);
assert!(matches.subcommand_matches("sub").is_some());

ArgRequiredElseHelp

Exit gracefully if no arguments are present (e.g. $ myprog).

NOTE: subcommands count as arguments

NOTE: Setting Arg::default_value effectively disables this option as it will ensure that some argument is always present.

Examples

App::new("myprog")
    .setting(AppSettings::ArgRequiredElseHelp);

DeriveDisplayOrder

Displays the arguments and subcommands in the help message in the order that they were declared in, and not alphabetically which is the default.

To override the declaration order, see Arg::display_order and App::display_order.

Examples

App::new("myprog")
    .global_setting(AppSettings::DeriveDisplayOrder)
    .get_matches();

DontCollapseArgsInUsage

Disables the automatic collapsing of positional args into [ARGS] inside the usage string.

Examples

App::new("myprog")
    .global_setting(AppSettings::DontCollapseArgsInUsage)
    .get_matches();

NextLineHelp

Places the help string for all arguments on the line after the argument.

Examples

App::new("myprog")
    .global_setting(AppSettings::NextLineHelp)
    .get_matches();

DisableColoredHelp

Disables colorized help messages.

Examples

App::new("myprog")
    .setting(AppSettings::DisableColoredHelp)
    .get_matches();

DisableHelpFlag

Disables -h and --help flag.

Examples

let res = App::new("myprog")
    .setting(AppSettings::DisableHelpFlag)
    .try_get_matches_from(vec![
        "myprog", "-h"
    ]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind, ErrorKind::UnknownArgument);

DisableHelpSubcommand

Disables the help subcommand.

Examples

let res = App::new("myprog")
    .setting(AppSettings::DisableHelpSubcommand)
    // Normally, creating a subcommand causes a `help` subcommand to automatically
    // be generated as well
    .subcommand(App::new("test"))
    .try_get_matches_from(vec![
        "myprog", "help"
    ]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind, ErrorKind::UnknownArgument);

DisableVersionFlag

Disables -V and --version flag.

Examples

let res = App::new("myprog")
    .setting(AppSettings::DisableVersionFlag)
    .try_get_matches_from(vec![
        "myprog", "-V"
    ]);
assert!(res.is_err());
assert_eq!(res.unwrap_err().kind, ErrorKind::UnknownArgument);

PropagateVersion

Specifies to use the version of the current command for all subcommands.

Defaults to false; subcommands have independent version strings from their parents.

Note: Make sure you apply it as global_setting if you want this setting to be propagated to subcommands and sub-subcommands!

Examples

App::new("myprog")
    .version("v1.1")
    .global_setting(AppSettings::PropagateVersion)
    .subcommand(App::new("test"))
    .get_matches();
// running `$ myprog test --version` will display
// "myprog-test v1.1"

Hidden

Specifies that this subcommand should be hidden from help messages

Examples

App::new("myprog")
    .subcommand(App::new("test")
    .setting(AppSettings::Hidden))

HidePossibleValues

Tells clap not to print possible values when displaying help information.

This can be useful if there are many values, or they are explained elsewhere.

To set this per argument, see Arg::hide_possible_values.

HelpExpected

Panic if help descriptions are omitted.

NOTE: When deriving Parser, you could instead check this at compile-time with #![deny(missing_docs)]

Examples

App::new("myprog")
    .global_setting(AppSettings::HelpExpected)
    .arg(
        Arg::new("foo").help("It does foo stuff")
        // As required via AppSettings::HelpExpected, a help message was supplied
     )

Panics

App::new("myapp")
    .global_setting(AppSettings::HelpExpected)
    .arg(
        Arg::new("foo")
        // Someone forgot to put .about("...") here
        // Since the setting AppSettings::HelpExpected is activated, this will lead to
        // a panic (if you are in debug mode)
    )

NoBinaryName

Specifies that the parser should not assume the first argument passed is the binary name.

This is normally the case when using a “daemon” style mode, or an interactive CLI where one would not normally type the binary or program name for each command.

Examples

let m = App::new("myprog")
    .setting(AppSettings::NoBinaryName)
    .arg(arg!(<cmd> ... "commands to run"))
    .get_matches_from(vec!["command", "set"]);

let cmds: Vec<&str> = m.values_of("cmd").unwrap().collect();
assert_eq!(cmds, ["command", "set"]);

NoAutoHelp

Treat the auto-generated -h, --help flags like any other flag, and not print the help message.

This allows one to handle printing of the help message manually.

let result = App::new("myprog")
    .setting(AppSettings::NoAutoHelp)
    .try_get_matches_from("myprog --help".split(" "));

// Normally, if `--help` is used clap prints the help message and returns an
// ErrorKind::DisplayHelp
//
// However, `--help` was treated like a normal flag

assert!(result.is_ok());
assert!(result.unwrap().is_present("help"));

NoAutoVersion

Treat the auto-generated -V, --version flags like any other flag, and not print the version message.

This allows one to handle printing of the version message manually.

let result = App::new("myprog")
    .version("3.0")
    .setting(AppSettings::NoAutoVersion)
    .try_get_matches_from("myprog --version".split(" "));

// Normally, if `--version` is used clap prints the version message and returns an
// ErrorKind::DisplayVersion
//
// However, `--version` was treated like a normal flag

assert!(result.is_ok());
assert!(result.unwrap().is_present("version"));

AllowLeadingHyphen

👎 Deprecated since 3.0.0:

Replaced with AppSettings::AllowHyphenValues

Deprecated, replaced with AppSettings::AllowHyphenValues

StrictUtf8

👎 Deprecated since 3.0.0:

This is now the default see AppSettings::AllowInvalidUtf8ForExternalSubcommands and ArgSettings::AllowInvalidUtf8 for the opposite.

Deprecated, this is now the default, see AppSettings::AllowInvalidUtf8ForExternalSubcommands and ArgSettings::AllowInvalidUtf8 for the opposite.

UnifiedHelpMessage

👎 Deprecated since 3.0.0:

This is now the default

Deprecated, this is now the default

ColoredHelp

👎 Deprecated since 3.0.0:

This is now the default

Deprecated, this is now the default

ColorAuto

👎 Deprecated since 3.0.0:

Replaced with App::color

Deprecated, see App::color

ColorAlways

👎 Deprecated since 3.0.0:

Replaced with App::color

Deprecated, replaced with App::color

ColorNever

👎 Deprecated since 3.0.0:

Replaced with App::color

Deprecated, replaced with App::color

DisableHelpFlags

👎 Deprecated since 3.0.0:

Replaced with AppSettings::DisableHelpFlag

Deprecated, replaced with AppSettings::DisableHelpFlag

DisableVersion

👎 Deprecated since 3.0.0:

Replaced with AppSettings::DisableVersionFlag

Deprecated, replaced with AppSettings::DisableVersionFlag

GlobalVersion

👎 Deprecated since 3.0.0:

Replaced with AppSettings::PropagateVersion

Deprecated, replaced with AppSettings::PropagateVersion

HidePossibleValuesInHelp

👎 Deprecated since 3.0.0:

Replaced with AppSettings::HidePossibleValues

Deprecated, replaced with AppSettings::HidePossibleValues

UnifiedHelp

👎 Deprecated since 3.0.0:

This is now the default

Deprecated, this is now the default

Trait Implementations

impl BitOr<AppSettings> for AppSettings

type Output = AppFlags

The resulting type after applying the | operator.

fn bitor(self, rhs: Self) -> Self::Output

Performs the | operation.

impl Clone for AppSettings

fn clone(&self) -> AppSettings

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for AppSettings

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

Formats the value using the given formatter.

impl PartialEq<AppSettings> for AppSettings

fn eq(&self, other: &AppSettings) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl Copy for AppSettings

impl StructuralPartialEq for AppSettings