Struct clap::ArgMatches

pub struct ArgMatches { /* fields omitted */ }

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 App::get_matches family of methods.

Examples

let matches = App::new("MyApp")
    .arg(Arg::new("out")
        .long("output")
        .required(true)
        .takes_value(true))
    .arg(Arg::new("debug")
        .short('d')
        .multiple_occurrences(true))
    .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::value_of
if let Some(c) = matches.value_of("cfg") {
    println!("Value for -c: {}", c);
}

// The ArgMatches::value_of 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.value_of("out").unwrap());

// You can check the presence of an argument
if matches.is_present("out") {
    // Another way to check if an argument was present, or if it occurred multiple times is to
    // use occurrences_of() which returns 0 if an argument isn't found at runtime, or the
    // number of times that it occurred, if it was. To allow an argument to appear more than
    // once, you must use the .multiple_occurrences(true) method, otherwise it will only return 1 or 0.
    if matches.occurrences_of("debug") > 2 {
        println!("Debug mode is REALLY on, don't be crazy");
    } else {
        println!("Debug mode kind of on");
    }
}

Implementations

impl ArgMatches

pub fn value_of<T: Key>(&self, id: T) -> Option<&str>

Gets the value of a specific option or positional argument.

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

Returns None if the option wasn’t present.

NOTE: Prefer ArgMatches::values_of if getting a value for an option or positional argument that allows multiples as ArgMatches::value_of will only return the first value.

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

Panics

If the value is invalid UTF-8. See Arg::allow_invalid_utf8.

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

Examples

let m = App::new("myapp")
    .arg(Arg::new("output")
        .takes_value(true))
    .get_matches_from(vec!["myapp", "something"]);

assert_eq!(m.value_of("output"), Some("something"));

pub fn value_of_lossy<T: Key>(&self, id: T) -> Option<Cow<'_, str>>

Gets the lossy value of a specific option or positional argument.

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

A lossy value is one which contains invalid UTF-8, those invalid points will be replaced with \u{FFFD}

Returns None if the option wasn’t present.

NOTE: Recommend having set Arg::allow_invalid_utf8.

NOTE: Prefer ArgMatches::values_of_lossy if getting a value for an option or positional argument that allows multiples as ArgMatches::value_of_lossy will only return the first value.

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

Panics

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

Examples

use std::ffi::OsString;
use std::os::unix::ffi::{OsStrExt,OsStringExt};

let m = App::new("utf8")
   .arg(arg!(<arg> "some arg")
       .allow_invalid_utf8(true))
   .get_matches_from(vec![OsString::from("myprog"),
                           // "Hi {0xe9}!"
                           OsString::from_vec(vec![b'H', b'i', b' ', 0xe9, b'!'])]);
assert_eq!(&*m.value_of_lossy("arg").unwrap(), "Hi \u{FFFD}!");

pub fn value_of_os<T: Key>(&self, id: T) -> Option<&OsStr>

Get the OsStr value of a specific option or positional argument.

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

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.

NOTE: Recommend having set Arg::allow_invalid_utf8.

NOTE: Prefer ArgMatches::values_of_os if getting a value for an option or positional argument that allows multiples as ArgMatches::value_of_os will only return the first value.

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

Panics

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

Examples

use std::ffi::OsString;
use std::os::unix::ffi::{OsStrExt,OsStringExt};

let m = App::new("utf8")
   .arg(arg!(<arg> "some arg")
       .allow_invalid_utf8(true))
   .get_matches_from(vec![OsString::from("myprog"),
                           // "Hi {0xe9}!"
                           OsString::from_vec(vec![b'H', b'i', b' ', 0xe9, b'!'])]);
assert_eq!(&*m.value_of_os("arg").unwrap().as_bytes(), [b'H', b'i', b' ', 0xe9, b'!']);

pub fn values_of<T: Key>(&self, id: T) -> Option<Values<'_>>

Get an Iterator over values of a specific option or positional argument.

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

Returns None if the option wasn’t present.

Panics

If the value is invalid UTF-8. See Arg::allow_invalid_utf8.

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

Examples

let m = App::new("myprog")
    .arg(Arg::new("output")
        .multiple_occurrences(true)
        .short('o')
        .takes_value(true))
    .get_matches_from(vec![
        "myprog", "-o", "val1", "-o", "val2", "-o", "val3"
    ]);
let vals: Vec<&str> = m.values_of("output").unwrap().collect();
assert_eq!(vals, ["val1", "val2", "val3"]);

pub fn grouped_values_of<T: Key>(&self, id: T) -> Option<GroupedValues<'_>>

Placeholder documentation.

pub fn values_of_lossy<T: Key>(&self, id: T) -> Option<Vec<String>>

Get the lossy values of a specific option or positional argument.

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

A lossy value is one which contains invalid UTF-8, those invalid points will be replaced with \u{FFFD}

Returns None if the option wasn’t present.

NOTE: Recommend having set Arg::allow_invalid_utf8.

Panics

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

Examples

use std::ffi::OsString;
use std::os::unix::ffi::OsStringExt;

let m = App::new("utf8")
   .arg(arg!(<arg> ... "some arg")
       .allow_invalid_utf8(true))
   .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.values_of_lossy("arg").unwrap().into_iter();
assert_eq!(&itr.next().unwrap()[..], "Hi");
assert_eq!(&itr.next().unwrap()[..], "\u{FFFD}!");
assert_eq!(itr.next(), None);

pub fn values_of_os<T: Key>(&self, id: T) -> Option<OsValues<'_>>

Get an Iterator over OsStr values of a specific option or positional argument.

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

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.

NOTE: Recommend having set Arg::allow_invalid_utf8.

Panics

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

Examples

use std::ffi::{OsStr,OsString};
use std::os::unix::ffi::{OsStrExt,OsStringExt};

let m = App::new("utf8")
   .arg(arg!(<arg> ... "some arg")
       .allow_invalid_utf8(true))
   .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.values_of_os("arg").unwrap().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);

pub fn value_of_t<R>(&self, name: &str) -> Result<R, Error> where
    R: FromStr,
    <R as FromStr>::Err: Display, 

Parse the value (with FromStr) of a specific option or positional argument.

There are two types of errors, parse failures and those where the argument wasn’t present (such as a non-required argument). Check ErrorKind to distinguish them.

NOTE: If getting a value for an option or positional argument that allows multiples, prefer ArgMatches::values_of_t as this method will only return the first value.

Panics

If the value is invalid UTF-8. See Arg::allow_invalid_utf8.

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

Examples

let matches = App::new("myapp")
              .arg(arg!([length] "Set the length to use as a pos whole num i.e. 20"))
              .get_matches_from(&["test", "12"]);

// Specify the type explicitly (or use turbofish)
let len: u32 = matches.value_of_t("length").unwrap_or_else(|e| e.exit());
assert_eq!(len, 12);

// You can often leave the type for rustc to figure out
let also_len = matches.value_of_t("length").unwrap_or_else(|e| e.exit());
// Something that expects u32
let _: u32 = also_len;

pub fn value_of_t_or_exit<R>(&self, name: &str) -> R where
    R: FromStr,
    <R as FromStr>::Err: Display, 

Parse the value (with FromStr) of a specific option or positional argument.

If either the value is not present or parsing failed, exits the program.

Panics

If the value is invalid UTF-8. See Arg::allow_invalid_utf8.

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

Examples

let matches = App::new("myapp")
              .arg(arg!([length] "Set the length to use as a pos whole num i.e. 20"))
              .get_matches_from(&["test", "12"]);

// Specify the type explicitly (or use turbofish)
let len: u32 = matches.value_of_t_or_exit("length");
assert_eq!(len, 12);

// You can often leave the type for rustc to figure out
let also_len = matches.value_of_t_or_exit("length");
// Something that expects u32
let _: u32 = also_len;

`FromStr

pub fn values_of_t<R>(&self, name: &str) -> Result<Vec<R>, Error> where
    R: FromStr,
    <R as FromStr>::Err: Display, 

Parse the values (with FromStr) of a specific option or positional argument.

There are two types of errors, parse failures and those where the argument wasn’t present (such as a non-required argument). Check ErrorKind to distinguish them.

NOTE: If getting a value for an option or positional argument that allows multiples, prefer ArgMatches::values_of_t as this method will only return the first value.

Panics

If the value is invalid UTF-8. See Arg::allow_invalid_utf8.

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

Examples

let matches = App::new("myapp")
              .arg(arg!([length] ... "A sequence of integers because integers are neat!"))
              .get_matches_from(&["test", "12", "77", "40"]);

// Specify the type explicitly (or use turbofish)
let len: Vec<u32> = matches.values_of_t("length").unwrap_or_else(|e| e.exit());
assert_eq!(len, vec![12, 77, 40]);

// You can often leave the type for rustc to figure out
let also_len = matches.values_of_t("length").unwrap_or_else(|e| e.exit());
// Something that expects Vec<u32>
let _: Vec<u32> = also_len;

pub fn values_of_t_or_exit<R>(&self, name: &str) -> Vec<R> where
    R: FromStr,
    <R as FromStr>::Err: Display, 

Parse the values (with FromStr) of a specific option or positional argument.

If parsing (of any value) has failed, exits the program.

Panics

If the value is invalid UTF-8. See Arg::allow_invalid_utf8.

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

Examples

let matches = App::new("myapp")
              .arg(arg!([length] ... "A sequence of integers because integers are neat!"))
              .get_matches_from(&["test", "12", "77", "40"]);

// Specify the type explicitly (or use turbofish)
let len: Vec<u32> = matches.values_of_t_or_exit("length");
assert_eq!(len, vec![12, 77, 40]);

// You can often leave the type for rustc to figure out
let also_len = matches.values_of_t_or_exit("length");
// Something that expects Vec<u32>
let _: Vec<u32> = also_len;

pub fn is_present<T: Key>(&self, id: T) -> bool

Check if an argument was present at runtime.

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

Panics

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

Examples

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

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

pub fn occurrences_of<T: Key>(&self, id: T) -> u64

The number of times an argument was used at runtime.

If an argument isn’t present it will return 0.

NOTE: This returns the number of times the argument was used, not the number of values. For example, -o val1 val2 val3 -o val4 would return 2 (2 occurrences, but 4 values). See Arg::multiple_occurrences.

Panics

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

Examples

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

assert_eq!(m.occurrences_of("debug"), 3);

This next example shows that counts actual uses of the argument, not just -’s

let m = App::new("myprog")
    .arg(Arg::new("debug")
        .short('d')
        .multiple_occurrences(true))
    .arg(Arg::new("flag")
        .short('f'))
    .get_matches_from(vec![
        "myprog", "-ddfd"
    ]);

assert_eq!(m.occurrences_of("debug"), 3);
assert_eq!(m.occurrences_of("flag"), 1);

pub fn index_of<T: Key>(&self, id: T) -> Option<usize>

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 name.

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 = App::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 = App::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 = App::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 = App::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 = App::new("myapp")
    .arg(Arg::new("option")
        .short('o')
        .use_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]);

pub fn indices_of<T: Key>(&self, id: T) -> Option<Indices<'_>>

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 name.

Examples

let m = App::new("myapp")
    .arg(Arg::new("option")
        .short('o')
        .use_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 = App::new("myapp")
    .arg(Arg::new("option")
        .short('o')
        .takes_value(true)
        .multiple_occurrences(true))
    .arg(Arg::new("flag")
        .short('f')
        .multiple_occurrences(true))
    .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<_>>(), &[3, 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 = App::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]);

pub fn subcommand(&self) -> Option<(&str, &ArgMatches)>

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 = App::new("git")
     .subcommand(App::new("clone"))
     .subcommand(App::new("push"))
     .subcommand(App::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 = 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 app_m.subcommand() {
    Some((external, sub_m)) => {
         let ext_args: Vec<&str> = sub_m.values_of("").unwrap().collect();
         assert_eq!(external, "subcmd");
         assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    },
    _ => {},
}

pub fn subcommand_matches<T: Key>(&self, id: T) -> Option<&ArgMatches>

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 = App::new("myprog")
    .arg(Arg::new("debug")
        .short('d'))
    .subcommand(App::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.is_present("debug"));

// 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.value_of("opt"), Some("val"));
}

pub fn subcommand_name(&self) -> Option<&str>

The name of the current subcommand.

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

Examples

 let app_m = App::new("git")
     .subcommand(App::new("clone"))
     .subcommand(App::new("push"))
     .subcommand(App::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...
}

Trait Implementations

impl Clone for ArgMatches

fn clone(&self) -> ArgMatches

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for ArgMatches

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

Formats the value using the given formatter.

impl Default for ArgMatches

fn default() -> ArgMatches

Returns the “default value” for a type.

impl PartialEq<ArgMatches> for ArgMatches

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

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

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

This method tests for !=.

impl Eq for ArgMatches

impl StructuralEq for ArgMatches

impl StructuralPartialEq for ArgMatches