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Struct clap::parser::ArgMatches

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pub struct ArgMatches { /* private fields */ }
Expand description

Container for parse results.

Used to get information about the arguments that were supplied to the program at runtime by the user. New instances of this struct are obtained by using the Command::get_matches family of methods.

Examples

let matches = Command::new("MyApp")
    .arg(Arg::new("out")
        .long("output")
        .required(true)
        .takes_value(true)
        .default_value("-"))
    .arg(Arg::new("cfg")
        .short('c')
        .takes_value(true))
    .get_matches(); // builds the instance of ArgMatches

// to get information about the "cfg" argument we created, such as the value supplied we use
// various ArgMatches methods, such as [ArgMatches::get_one]
if let Some(c) = matches.get_one::<String>("cfg") {
    println!("Value for -c: {}", c);
}

// The ArgMatches::get_one method returns an Option because the user may not have supplied
// that argument at runtime. But if we specified that the argument was "required" as we did
// with the "out" argument, we can safely unwrap because `clap` verifies that was actually
// used at runtime.
println!("Value for --output: {}", matches.get_one::<String>("out").unwrap());

// You can check the presence of an argument's values
if matches.contains_id("out") {
    // However, if you want to know where the value came from
    if matches.value_source("out").expect("checked contains_id") == ValueSource::CommandLine {
        println!("`out` set by user");
    } else {
        println!("`out` is defaulted");
    }
}

Implementations

Arguments

Gets the value of a specific option or positional argument.

i.e. an argument that takes an additional value at runtime.

Returns an error if the wrong type was used.

Returns None if the option wasn’t present.

NOTE: This will always return Some(value) if default_value has been set. ArgMatches::value_source can be used to check if a value is present at runtime.

Panic

If the argument definition and access mismatch. To handle this case programmatically, see ArgMatches::try_get_one.

Examples
let m = Command::new("myapp")
    .arg(Arg::new("port")
        .value_parser(value_parser!(usize))
        .takes_value(true)
        .required(true))
    .get_matches_from(vec!["myapp", "2020"]);

let port: usize = *m
    .get_one("port")
    .expect("`port`is required");
assert_eq!(port, 2020);

Iterate over values of a specific option or positional argument.

i.e. an argument that takes multiple values at runtime.

Returns an error if the wrong type was used.

Returns None if the option wasn’t present.

Panic

If the argument definition and access mismatch. To handle this case programmatically, see ArgMatches::try_get_many.

Examples
let m = Command::new("myprog")
    .arg(Arg::new("ports")
        .action(ArgAction::Append)
        .value_parser(value_parser!(usize))
        .short('p')
        .takes_value(true)
        .required(true))
    .get_matches_from(vec![
        "myprog", "-p", "22", "-p", "80", "-p", "2020"
    ]);
let vals: Vec<usize> = m.get_many("ports")
    .expect("`port`is required")
    .copied()
    .collect();
assert_eq!(vals, [22, 80, 2020]);

Iterate over the original argument values.

An OsStr on Unix-like systems is any series of bytes, regardless of whether or not they contain valid UTF-8. Since Strings in Rust are guaranteed to be valid UTF-8, a valid filename on a Unix system as an argument value may contain invalid UTF-8.

Returns None if the option wasn’t present.

Panic

If the argument definition and access mismatch. To handle this case programmatically, see ArgMatches::try_get_raw.

Examples
use std::path::PathBuf;

let m = Command::new("utf8")
   .arg(arg!(<arg> ... "some arg").value_parser(value_parser!(PathBuf)))
   .get_matches_from(vec![OsString::from("myprog"),
                               // "Hi"
                               OsString::from_vec(vec![b'H', b'i']),
                               // "{0xe9}!"
                               OsString::from_vec(vec![0xe9, b'!'])]);

let mut itr = m.get_raw("arg")
   .expect("`port`is required")
   .into_iter();
assert_eq!(itr.next(), Some(OsStr::new("Hi")));
assert_eq!(itr.next(), Some(OsStr::from_bytes(&[0xe9, b'!'])));
assert_eq!(itr.next(), None);

Returns the value of a specific option or positional argument.

i.e. an argument that takes an additional value at runtime.

Returns an error if the wrong type was used. No item will have been removed.

Returns None if the option wasn’t present.

NOTE: This will always return Some(value) if default_value has been set. ArgMatches::value_source can be used to check if a value is present at runtime.

Panic

If the argument definition and access mismatch. To handle this case programmatically, see ArgMatches::try_remove_one.

Examples
let mut m = Command::new("myprog")
    .arg(Arg::new("file")
        .required(true)
        .takes_value(true))
    .get_matches_from(vec![
        "myprog", "file.txt",
    ]);
let vals: String = m.remove_one("file")
    .expect("`file`is required");
assert_eq!(vals, "file.txt");

Return values of a specific option or positional argument.

i.e. an argument that takes multiple values at runtime.

Returns an error if the wrong type was used. No item will have been removed.

Returns None if the option wasn’t present.

Panic

If the argument definition and access mismatch. To handle this case programmatically, see ArgMatches::try_remove_many.

Examples
let mut m = Command::new("myprog")
    .arg(Arg::new("file")
        .action(ArgAction::Append)
        .multiple_values(true)
        .required(true)
        .takes_value(true))
    .get_matches_from(vec![
        "myprog", "file1.txt", "file2.txt", "file3.txt", "file4.txt",
    ]);
let vals: Vec<String> = m.remove_many("file")
    .expect("`file`is required")
    .collect();
assert_eq!(vals, ["file1.txt", "file2.txt", "file3.txt", "file4.txt"]);

Check if values are present for the argument or group id

NOTE: This will always return true if default_value has been set. ArgMatches::value_source can be used to check if a value is present at runtime.

Panics

If id is is not a valid argument or group name. To handle this case programmatically, see ArgMatches::try_contains_id.

Examples
let m = Command::new("myprog")
    .arg(Arg::new("debug")
        .short('d'))
    .get_matches_from(vec![
        "myprog", "-d"
    ]);

assert!(m.contains_id("debug"));

Check if any args were present on the command line

Examples
let mut cmd = Command::new("myapp")
    .arg(Arg::new("output")
        .takes_value(true));

let m = cmd
    .try_get_matches_from_mut(vec!["myapp", "something"])
    .unwrap();
assert!(m.args_present());

let m = cmd
    .try_get_matches_from_mut(vec!["myapp"])
    .unwrap();
assert!(! m.args_present());

Deprecated, replaced with ArgMatches::get_one()

Deprecated, replaced with ArgMatches::get_one()

Deprecated, replaced with ArgMatches::get_one()

Deprecated, replaced with ArgMatches::get_many()

Deprecated, replaced with ArgMatches::get_many()

Deprecated, replaced with ArgMatches::get_many()

Deprecated, replaced with ArgMatches::get_one()

Deprecated, replaced with ArgMatches::get_one()

Deprecated, replaced with ArgMatches::get_many()

Deprecated, replaced with ArgMatches::get_many()

Deprecated, replaced with ArgAction::SetTrue or ArgMatches::contains_id.

Report where argument value came from

Panics

If id is is not a valid argument or group id.

Examples
let m = Command::new("myprog")
    .arg(Arg::new("debug")
        .short('d'))
    .get_matches_from(vec![
        "myprog", "-d"
    ]);

assert_eq!(m.value_source("debug"), Some(ValueSource::CommandLine));

Deprecated, replaced with ArgAction::Count, ArgMatches::get_many.len(), or ArgMatches::value_source.

The first index of that an argument showed up.

Indices are similar to argv indices, but are not exactly 1:1.

For flags (i.e. those arguments which don’t have an associated value), indices refer to occurrence of the switch, such as -f, or --flag. However, for options the indices refer to the values -o val would therefore not represent two distinct indices, only the index for val would be recorded. This is by design.

Besides the flag/option discrepancy, the primary difference between an argv index and clap index, is that clap continues counting once all arguments have properly separated, whereas an argv index does not.

The examples should clear this up.

NOTE: If an argument is allowed multiple times, this method will only give the first index. See ArgMatches::indices_of.

Panics

If id is is not a valid argument or group id.

Examples

The argv indices are listed in the comments below. See how they correspond to the clap indices. Note that if it’s not listed in a clap index, this is because it’s not saved in in an ArgMatches struct for querying.

let m = Command::new("myapp")
    .arg(Arg::new("flag")
        .short('f'))
    .arg(Arg::new("option")
        .short('o')
        .takes_value(true))
    .get_matches_from(vec!["myapp", "-f", "-o", "val"]);
           // ARGV indices: ^0       ^1    ^2    ^3
           // clap indices:          ^1          ^3

assert_eq!(m.index_of("flag"), Some(1));
assert_eq!(m.index_of("option"), Some(3));

Now notice, if we use one of the other styles of options:

let m = Command::new("myapp")
    .arg(Arg::new("flag")
        .short('f'))
    .arg(Arg::new("option")
        .short('o')
        .takes_value(true))
    .get_matches_from(vec!["myapp", "-f", "-o=val"]);
           // ARGV indices: ^0       ^1    ^2
           // clap indices:          ^1       ^3

assert_eq!(m.index_of("flag"), Some(1));
assert_eq!(m.index_of("option"), Some(3));

Things become much more complicated, or clear if we look at a more complex combination of flags. Let’s also throw in the final option style for good measure.

let m = Command::new("myapp")
    .arg(Arg::new("flag")
        .short('f'))
    .arg(Arg::new("flag2")
        .short('F'))
    .arg(Arg::new("flag3")
        .short('z'))
    .arg(Arg::new("option")
        .short('o')
        .takes_value(true))
    .get_matches_from(vec!["myapp", "-fzF", "-oval"]);
           // ARGV indices: ^0      ^1       ^2
           // clap indices:         ^1,2,3    ^5
           //
           // clap sees the above as 'myapp -f -z -F -o val'
           //                         ^0    ^1 ^2 ^3 ^4 ^5
assert_eq!(m.index_of("flag"), Some(1));
assert_eq!(m.index_of("flag2"), Some(3));
assert_eq!(m.index_of("flag3"), Some(2));
assert_eq!(m.index_of("option"), Some(5));

One final combination of flags/options to see how they combine:

let m = Command::new("myapp")
    .arg(Arg::new("flag")
        .short('f'))
    .arg(Arg::new("flag2")
        .short('F'))
    .arg(Arg::new("flag3")
        .short('z'))
    .arg(Arg::new("option")
        .short('o')
        .takes_value(true))
    .get_matches_from(vec!["myapp", "-fzFoval"]);
           // ARGV indices: ^0       ^1
           // clap indices:          ^1,2,3^5
           //
           // clap sees the above as 'myapp -f -z -F -o val'
           //                         ^0    ^1 ^2 ^3 ^4 ^5
assert_eq!(m.index_of("flag"), Some(1));
assert_eq!(m.index_of("flag2"), Some(3));
assert_eq!(m.index_of("flag3"), Some(2));
assert_eq!(m.index_of("option"), Some(5));

The last part to mention is when values are sent in multiple groups with a delimiter.

let m = Command::new("myapp")
    .arg(Arg::new("option")
        .short('o')
        .use_value_delimiter(true)
        .multiple_values(true))
    .get_matches_from(vec!["myapp", "-o=val1,val2,val3"]);
           // ARGV indices: ^0       ^1
           // clap indices:             ^2   ^3   ^4
           //
           // clap sees the above as 'myapp -o val1 val2 val3'
           //                         ^0    ^1 ^2   ^3   ^4
assert_eq!(m.index_of("option"), Some(2));
assert_eq!(m.indices_of("option").unwrap().collect::<Vec<_>>(), &[2, 3, 4]);

All indices an argument appeared at when parsing.

Indices are similar to argv indices, but are not exactly 1:1.

For flags (i.e. those arguments which don’t have an associated value), indices refer to occurrence of the switch, such as -f, or --flag. However, for options the indices refer to the values -o val would therefore not represent two distinct indices, only the index for val would be recorded. This is by design.

NOTE: For more information about how clap indices compared to argv indices, see ArgMatches::index_of

Panics

If id is is not a valid argument or group id.

Examples
let m = Command::new("myapp")
    .arg(Arg::new("option")
        .short('o')
        .use_value_delimiter(true)
        .multiple_values(true))
    .get_matches_from(vec!["myapp", "-o=val1,val2,val3"]);
           // ARGV indices: ^0       ^1
           // clap indices:             ^2   ^3   ^4
           //
           // clap sees the above as 'myapp -o val1 val2 val3'
           //                         ^0    ^1 ^2   ^3   ^4
assert_eq!(m.indices_of("option").unwrap().collect::<Vec<_>>(), &[2, 3, 4]);

Another quick example is when flags and options are used together

let m = Command::new("myapp")
    .arg(Arg::new("option")
        .short('o')
        .takes_value(true)
        .action(ArgAction::Append))
    .arg(Arg::new("flag")
        .short('f')
        .action(ArgAction::Count))
    .get_matches_from(vec!["myapp", "-o", "val1", "-f", "-o", "val2", "-f"]);
           // ARGV indices: ^0       ^1    ^2      ^3    ^4    ^5      ^6
           // clap indices:                ^2      ^3          ^5      ^6

assert_eq!(m.indices_of("option").unwrap().collect::<Vec<_>>(), &[2, 5]);
assert_eq!(m.indices_of("flag").unwrap().collect::<Vec<_>>(), &[6]);

One final example, which is an odd case; if we don’t use value delimiter as we did with the first example above instead of val1, val2 and val3 all being distinc values, they would all be a single value of val1,val2,val3, in which case they’d only receive a single index.

let m = Command::new("myapp")
    .arg(Arg::new("option")
        .short('o')
        .takes_value(true)
        .multiple_values(true))
    .get_matches_from(vec!["myapp", "-o=val1,val2,val3"]);
           // ARGV indices: ^0       ^1
           // clap indices:             ^2
           //
           // clap sees the above as 'myapp -o "val1,val2,val3"'
           //                         ^0    ^1  ^2
assert_eq!(m.indices_of("option").unwrap().collect::<Vec<_>>(), &[2]);

Subcommands

The name and ArgMatches of the current subcommand.

Subcommand values are put in a child ArgMatches

Returns None if the subcommand wasn’t present at runtime,

Examples
 let app_m = Command::new("git")
     .subcommand(Command::new("clone"))
     .subcommand(Command::new("push"))
     .subcommand(Command::new("commit"))
     .get_matches();

match app_m.subcommand() {
    Some(("clone",  sub_m)) => {}, // clone was used
    Some(("push",   sub_m)) => {}, // push was used
    Some(("commit", sub_m)) => {}, // commit was used
    _                       => {}, // Either no subcommand or one not tested for...
}

Another useful scenario is when you want to support third party, or external, subcommands. In these cases you can’t know the subcommand name ahead of time, so use a variable instead with pattern matching!

// Assume there is an external subcommand named "subcmd"
let app_m = Command::new("myprog")
    .allow_external_subcommands(true)
    .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 app_m.subcommand() {
    Some((external, sub_m)) => {
         let ext_args: Vec<&str> = sub_m.get_many::<String>("")
            .unwrap().map(|s| s.as_str()).collect();
         assert_eq!(external, "subcmd");
         assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    },
    _ => {},
}

Return the name and ArgMatches of the current subcommand.

Subcommand values are put in a child ArgMatches

Returns None if the subcommand wasn’t present at runtime,

Examples
 let mut app_m = Command::new("git")
     .subcommand(Command::new("clone"))
     .subcommand(Command::new("push"))
     .subcommand(Command::new("commit"))
     .subcommand_required(true)
     .get_matches();

let (name, sub_m) = app_m.remove_subcommand().expect("required");
match (name.as_str(), sub_m) {
    ("clone",  sub_m) => {}, // clone was used
    ("push",   sub_m) => {}, // push was used
    ("commit", sub_m) => {}, // commit was used
    (name, _)         => unimplemented!("{}", name),
}

Another useful scenario is when you want to support third party, or external, subcommands. In these cases you can’t know the subcommand name ahead of time, so use a variable instead with pattern matching!

// Assume there is an external subcommand named "subcmd"
let mut app_m = Command::new("myprog")
    .allow_external_subcommands(true)
    .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 app_m.remove_subcommand() {
    Some((external, mut sub_m)) => {
         let ext_args: Vec<String> = sub_m.remove_many("")
            .expect("`file`is required")
            .collect();
         assert_eq!(external, "subcmd");
         assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    },
    _ => {},
}

The ArgMatches for the current subcommand.

Subcommand values are put in a child ArgMatches

Returns None if the subcommand wasn’t present at runtime,

Panics

If id is is not a valid subcommand.

Examples
let app_m = Command::new("myprog")
    .arg(Arg::new("debug")
        .short('d')
        .action(ArgAction::SetTrue)
    )
    .subcommand(Command::new("test")
        .arg(Arg::new("opt")
            .long("option")
            .takes_value(true)))
    .get_matches_from(vec![
        "myprog", "-d", "test", "--option", "val"
    ]);

// Both parent commands, and child subcommands can have arguments present at the same times
assert!(*app_m.get_one::<bool>("debug").expect("defaulted by clap"));

// Get the subcommand's ArgMatches instance
if let Some(sub_m) = app_m.subcommand_matches("test") {
    // Use the struct like normal
    assert_eq!(sub_m.get_one::<String>("opt").map(|s| s.as_str()), Some("val"));
}

The name of the current subcommand.

Returns None if the subcommand wasn’t present at runtime,

Examples
 let app_m = Command::new("git")
     .subcommand(Command::new("clone"))
     .subcommand(Command::new("push"))
     .subcommand(Command::new("commit"))
     .get_matches();

match app_m.subcommand_name() {
    Some("clone")  => {}, // clone was used
    Some("push")   => {}, // push was used
    Some("commit") => {}, // commit was used
    _              => {}, // Either no subcommand or one not tested for...
}

Advanced

Non-panicking version of ArgMatches::get_one

Non-panicking version of ArgMatches::get_many

Non-panicking version of ArgMatches::get_raw

Non-panicking version of ArgMatches::remove_one

Non-panicking version of ArgMatches::remove_many

Non-panicking version of ArgMatches::contains_id

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Returns the “default value” for a type. Read more

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

This method tests for !=.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Compare self to key and return true if they are equal.

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.