Struct clap::Arg
[−]
[src]
pub struct Arg<'a, 'b> where 'a: 'b {
// some fields omitted
}
The abstract representation of a command line argument. Used to set all the options and relationships that define a valid argument for the program.
There are two methods for constructing Arg
s, using the builder pattern and setting options
manually, or using a usage string which is far less verbose but has fewer options. You can also
use a combination of the two methods to achieve the best of both worlds.
Examples
// Using the traditional builder pattern and setting each option manually let cfg = Arg::with_name("config") .short("c") .long("config") .takes_value(true) .value_name("FILE") .help("Provides a config file to myprog"); // Using a usage string (setting a similar argument to the one above) let input = Arg::from_usage("-i, --input=[FILE] 'Provides an input file to the program'");
Methods
impl<'a, 'b> Arg<'a, 'b>
[src]
fn with_name(n: &'a str) -> Self
Creates a new instance of Arg
using a unique string name. The name will be used to get
information about whether or not the argument was used at runtime, get values, set
relationships with other args, etc..
NOTE: In the case of arguments that take values (i.e. takes_value(true)
)
and positional arguments (i.e. those without a preceding -
or --
) the name will also
be displayed when the user prints the usage/help information of the program.
Examples
Arg::with_name("config")
fn from_usage(u: &'a str) -> Self
Creates a new instance of Arg
from a usage string. Allows creation of basic settings for
the Arg
. The syntax is flexible, but there are some rules to follow.
NOTE: Not all settings may be set using the usage string method. Some properties are only available via the builder pattern.
NOTE: Only ASCII values in from_usage
strings are officially supported. Some UTF-8
codepoints may work just fine, but this is not guaranteed.
Syntax
Usage strings typically following the form:
[explicit name] [short] [long] [value names] [help string]
This is not a hard rule as the attributes can appear in other orders. There are also several additional sigils which denote additional settings. Below are the details of each portion of the string.
Explicit Name
This is an optional field, if it's omitted the argumenet will use one of the additioinal fields as the name using the following priority order:
- Explicit Name (This always takes precedence when present)
- Long
- Short
- Value Name
clap
determines explicit names as the first string of characters between either []
or
<>
where []
has the dual notation of meaning the argument is optional, and <>
meaning
the argument is required.
Explicit names may be followed by:
* The multiple denotation ...
Example explicit names as follows (ename
for an optional argument, and rname
for a
required argument):
[ename] -s, --long 'some flag'
<rname> -r, --longer 'some other flag'
Short
This is set by placing a single character after a leading -
.
Shorts may be followed by
* The multiple denotation ...
* An optional comma ,
which is cosmetic only
* Value notation
Example shorts are as follows (-s
, and -r
):
-s, --long 'some flag'
<rname> -r [val], --longer 'some option'
Long
This is set by placing a word (no spaces) after a leading --
.
Shorts may be followed by
* The multiple denotation ...
* Value notation
Example longs are as follows (--some
, and --rapid
):
-s, --some 'some flag'
--rapid=[FILE] 'some option'
Values (Value Notation)
This is set by placing a word(s) between []
or <>
optionally after =
(although this
is cosmetic only and does not affect functionality). If an explicit name has not been
set, using <>
will denote a required argument, and []
will denote an optional argument
Values may be followed by
* The multiple denotation ...
* More Value notation
More than one value will also implicitly set the arguments number of values, i.e. having
two values, --option [val1] [val2]
specifies that in order for option to be satisified it
must receive exactly two values
Example values are as follows (FILE
, and SPEED
):
-s, --some [FILE] 'some option'
--rapid=<SPEED>... 'some required multiple option'
Help String
The help string is denoted between a pair of single quotes ''
and may contain any characters.
Example help strings are as follows:
-s, --some [FILE] 'some option'
--rapid=<SPEED>... 'some required multiple option'
Additional Sigils
Multiple notation ...
(three consecutive dots/periods) specifies that this argument may
be used multiple times. Do not confuse multiple occurrences (...
) with multiple values.
--option val1 val2
is a single occurrence with multiple values. --flag --flag
is
multiple occurrences (and then you can obviously have instances of both as well)
Examples
App::new("myprog") .args(&[ Arg::from_usage("--config <FILE> 'a required file for the configuration and no short'"), Arg::from_usage("-d, --debug... 'turns on debugging information and allows multiples'"), Arg::from_usage("[input] 'an optional input file to use'") ])
fn short<S: AsRef<str>>(self, s: S) -> Self
Sets the short version of the argument without the preceding -
.
By default clap
automatically assigns V
and h
to display version and help information
respectively. You may use V
or h
for your own purposes, in which case clap
simply
will not assign those to the displaying of version or help.
NOTE: Any leading -
characters will be stripped, and only the first
non -
character will be used as the short
version
Examples
Arg::with_name("config") .short("c")
fn long(self, l: &'b str) -> Self
Sets the long version of the argument without the preceding --
.
By default clap
automatically assigns version
and help
to display version and help
information respectively. You may use version
or help
for your own purposes, in which
case clap
simply will not assign those to the displaying of version or help automatically,
and you will have to do so manually.
NOTE: Any leading -
characters will be stripped
Examples
Arg::with_name("cfg") .long("config")
fn help(self, h: &'b str) -> Self
Sets the help text of the argument that will be displayed to the user when they print the usage/help information.
Examples
Arg::with_name("config") .help("The config file used by the myprog")
fn required(self, r: bool) -> Self
Sets whether or not the argument is required by default. Required by default means it is required, when no other conflicting rules have been evaluated. Conflicting rules take precedence over being required.
NOTE: Flags (i.e. not positional, or arguments that take values) cannot be required.
Example
Arg::with_name("config") .required(true)
fn conflicts_with(self, name: &'a str) -> Self
Sets a conflicting argument by name. I.e. when using this argument, the following argument can't be present and vice versa.
NOTE: Conflicting rules take precedence over being required by default. Conflict rules only need to be set for one of the two arguments, they do not need to be set for each.
Examples
Arg::with_name("debug"); // ... Arg::with_name("config") .conflicts_with("debug")
fn conflicts_with_all(self, names: &[&'a str]) -> Self
Sets multiple conflicting arguments by names. I.e. when using this argument, the following arguments can't be present.
NOTE: Conflicting rules take precedence over being required by default. Conflict rules only need to be set for one of the two arguments, they do not need to be set for each.
Examples
Arg::with_name("debug"); Arg::with_name("input"); // ... Arg::with_name("config") .conflicts_with_all(&["debug", "input"])
fn overrides_with(self, name: &'a str) -> Self
Sets a overridable argument by name. I.e. this argument and the following argument will override each other in POSIX style (whichever argument was specified at runtime last "wins")
NOTE: When an argument is overriden it is essentially as if it never was used, any conflicts, requirements, etc. are evaluated after all "overrides" have been removed
Examples
let res = App::new("posix") .arg(Arg::from_usage("-f, --flag 'some flag'") .conflicts_with("debug")) .arg(Arg::from_usage("-d, --debug 'other flag'")) .arg(Arg::from_usage("-c, --color 'third flag'") .overrides_with("flag")) .get_matches_from_safe(vec!["", "-f", "-d", "-c"]); // ^~~~~~~~~~~~^~~~~ flag is overriden by --color assert!(res.is_ok()); let m = res.unwrap(); assert!(m.is_present("color")); assert!(m.is_present("debug")); assert!(!m.is_present("flag"));
fn overrides_with_all(self, names: &[&'a str]) -> Self
Sets a mutually overridable argument by name. I.e. this argument and the following argument will override each other in POSIX style (whichever argument was specified at runtime last "wins")
NOTE: When an argument is overriden it is essentially as if it never was used, any conflicts, requirements, etc. are evaluated after all "overrides" have been removed
Examples
let res = App::new("posix") .arg(Arg::from_usage("-f, --flag 'some flag'") .conflicts_with("debug")) .arg(Arg::from_usage("-d, --debug 'other flag'")) .arg(Arg::from_usage("-c, --color 'third flag'") .overrides_with_all(&["flag", "debug"])) .get_matches_from_safe(vec!["posix", "-f", "-d", "-c"]); // ^~~~~~^~~~~~^~~~~ flag and debug are overriden by --color assert!(res.is_ok()); let m = res.unwrap(); assert!(m.is_present("color")); assert!(!m.is_present("debug")); assert!(!m.is_present("flag"));
fn requires(self, name: &'a str) -> Self
Sets an argument by name that is required when this one is present I.e. when using this argument, the following argument must be present.
NOTE: Conflicting rules and override rules take precedence over being required
Examples
let m = App::new("group_required") .arg(Arg::from_usage("-f, --flag 'some flag'")) .group(ArgGroup::with_name("gr") .required(true) .arg("some") .arg("other")) .arg(Arg::from_usage("--some 'some arg'")) .arg(Arg::from_usage("--other 'other arg'")) .get_matches_from(vec!["", "-f", "--some"]); assert!(m.is_present("some")); assert!(!m.is_present("other")); assert!(m.is_present("flag"));
fn requires_all(self, names: &[&'a str]) -> Self
Sets arguments by names that are required when this one is present I.e. when using this argument, the following arguments must be present.
NOTE: Mutually exclusive and override rules take precedence over being required by default.
Examples
let result = App::new("flag_required") .arg(Arg::from_usage("-d 'debugging mode'")) .arg(Arg::from_usage("-f, --flag 'some flag'") .requires_all(&["color", "d"])) .arg(Arg::from_usage("-c, --color 'third flag'")) .get_matches_from_safe(vec!["flag_required", "-f"]); assert!(result.is_err()); let err = result.err().unwrap(); assert_eq!(err.kind, ErrorKind::MissingRequiredArgument);
fn takes_value(self, tv: bool) -> Self
Specifies that the argument takes an additional value at run time.
Examples
Arg::with_name("config") .takes_value(true)
fn index(self, idx: u8) -> Self
Specifies the index of a positional argument starting at 1.
Examples
Arg::with_name("file") .index(1)
fn multiple(self, multi: bool) -> Self
Specifies that the flag or option may appear more than once. For flags, this results
in the number of occurrences of the flag being recorded. For example -ddd
would count as
three occurrences. The form -d -d -d
would also be recognized as three occurrences. For
options there is a distinct difference in multiple occurrences vs multiple values.
For example, --opt val1 val2
is one occurrence, but multiple values. --opt val1 --opt val2
is multiple occurrences. This setting applies to occurrences and not values.
To specify that an option may receive multiple values, use Arg::min_values
,
Arg::max_values
, or Arg::number_of_values
depending on your use case. Note also, that
Arg::value_names
implicitly sets multiple values, but not multiple occurrences.
Examples
Arg::with_name("debug") .short("d") .multiple(true)
fn global(self, g: bool) -> Self
Specifies that an argument can be matched to all child subcommands.
NOTE: Global arguments only propagate down, not up (to parent commands)
NOTE: Global arguments cannot be required.
NOTE: Global arguments, when matched, only exist in the command's matches that they
were matched to. For example, if you defined a --flag
global argument in the top most
parent command, but the user supplied the arguments top cmd1 cmd2 --flag
only cmd2
's
ArgMatches
would return true
if tested for .is_present("flag")
.
Examples
Arg::with_name("debug") .short("d") .global(true)
fn empty_values(self, ev: bool) -> Self
Allows an argument to accept explicit empty values. An empty value must be specified at the
command line with an explicit ""
, or ''
NOTE: Defaults to true
(Explicit empty values are allowed)
NOTE: Implicitly sets takes_value(true)
when set to false
Examples
Arg::with_name("file") .long("file") .empty_values(false)
fn hidden(self, h: bool) -> Self
Hides an argument from help message output.
NOTE: This does not hide the argument from usage strings on error
Examples
Arg::with_name("debug") .hidden(true)
fn possible_values(self, names: &[&'b str]) -> Self
Specifies a list of possible values for this argument. At runtime, clap
verifies that only
one of the specified values was used, or fails with an error message.
NOTE: This setting only applies to options and positional arguments
Examples
let res = App::new("possible_values") .arg(Arg::with_name("option") .short("-o") .long("--option") .takes_value(true) .possible_values(&["fast", "slow"])) .get_matches_from_safe(vec!["myprog", "--option", "fast"]); assert!(res.is_ok()); let m = res.unwrap(); assert!(m.is_present("option")); assert_eq!(m.value_of("option"), Some("fast"));
The next example shows a failed parse
let res = App::new("possible_values") .arg(Arg::with_name("option") .short("-o") .long("--option") .takes_value(true) .possible_values(&["fast", "slow"])) .get_matches_from_safe(vec!["myprog", "--option", "wrong"]); assert!(res.is_err()); let err = res.unwrap_err(); assert_eq!(err.kind, ErrorKind::InvalidValue);
fn possible_value(self, name: &'b str) -> Self
Specifies a possible value for this argument. At runtime, clap
verifies that only
one of the specified values was used, or fails with error message.
Examples
let res = App::new("possible_values") .arg(Arg::with_name("option") .short("-o") .long("--option") .takes_value(true) .possible_value("slow") .possible_value("fast")) .get_matches_from_safe(vec!["myprog", "--option", "fast"]); assert!(res.is_ok()); let m = res.unwrap(); assert!(m.is_present("option")); assert_eq!(m.value_of("option"), Some("fast"));
The next example shows a failed parse
let res = App::new("possible_values") .arg(Arg::with_name("option") .short("-o") .long("--option") .takes_value(true) .possible_value("slow") .possible_value("fast")) .get_matches_from_safe(vec!["myprog", "--option", "wrong"]); assert!(res.is_err()); let err = res.unwrap_err(); assert_eq!(err.kind, ErrorKind::InvalidValue);
fn group(self, name: &'a str) -> Self
Specifies the name of the group the argument belongs to.
Examples
Arg::with_name("debug") .index(1) .group("mode")
fn number_of_values(self, qty: u8) -> Self
Specifies how many values are required to satisfy this argument. For example, if you had a
-f <file>
argument where you wanted exactly 3 'files' you would set
.number_of_values(3)
, and this argument wouldn't be satisfied unless the user provided
3 and only 3 values.
NOTE: Does not require .multiple(true)
to be set. Setting .multiple(true)
would
allow -f <file> <file> <file> -f <file> <file> <file>
where as not setting
.multiple(true)
would only allow one occurrence of this argument.
Examples
Arg::with_name("file") .short("f") .number_of_values(3)
fn validator<F>(self, f: F) -> Self where F: Fn(String) -> Result<(), String> + 'static
Allows one to perform a custom validation on the argument value. You provide a closure which
accepts a String
value, a Result
where the Err(String)
is a message displayed to the
user.
NOTE: The error message does not need to contain the error:
portion, only the
message.
NOTE: There is a small performance hit for using validators, as they are implemented
with Rc
pointers. And the value to be checked will be allocated an extra time in order to
to be passed to the closure. This performance hit is extremely minimal in the grand scheme
of things.
Examples
fn has_at(v: String) -> Result<(), String> { if v.contains("@") { return Ok(()); } Err(String::from("The value did not contain the required @ sigil")) } let res = App::new("validators") .arg(Arg::with_name("file") .index(1) .validator(has_at)) .get_matches_from_safe(vec![ "validators", "some@file" ]); assert!(res.is_ok()); assert_eq!(res.unwrap().value_of("file"), Some("some@file"));
fn max_values(self, qty: u8) -> Self
Specifies the maximum number of values are for this argument. For example, if you had a
-f <file>
argument where you wanted up to 3 'files' you would set
.max_values(3)
, and this argument would be satisfied if the user provided, 1, 2, or 3
values.
NOTE: This does not implicitly set mulitple(true)
. This is because -o val -o val
is
multiples occurrences but a single value and -o val1 val2
is a single occurence with
multple values. For positional arguments this does set multiple(true)
because there
is no way to determine the diffrence between multiple occureces and multiple values.
Examples
Arg::with_name("file") .short("f") .max_values(3)
fn min_values(self, qty: u8) -> Self
Specifies the minimum number of values are for this argument. For example, if you had a
-f <file>
argument where you wanted at least 2 'files' you would set
.min_values(2)
, and this argument would be satisfied if the user provided, 2 or more
values.
NOTE: This does not implicitly set mulitple(true)
. This is because -o val -o val
is
multiples occurrences but a single value and -o val1 val2
is a single occurence with
multple values. For positional arguments this does set multiple(true)
because there
is no way to determine the diffrence between multiple occureces and multiple values.
Examples
Arg::with_name("file") .short("f") .min_values(3)
fn use_delimiter(self, d: bool) -> Self
Specifies whether or not an arugment should allow grouping of multiple values via a
delimter. I.e. shoulde --option=val1,val2,val3
be parsed as three values (val1
, val2
,
and val3
) or as a single value (val1,val2,val3
). Defaults to using ,
(comma) as the
value delimiter for all arguments that accept values (options and positional arguments)
NOTE: The defalt is true
. Setting the value to true
will reset any previous use of
Arg::value_delimiter
back to the default of ,
(comma).
Examples
The following example shows the default behavior.
let delims = App::new("delims") .arg(Arg::with_name("option") .long("option") .takes_value(true)) .get_matches_from(vec![ "delims", "--option=val1,val2,val3", ]); assert!(delims.is_present("option")); assert_eq!(delims.occurrences_of("option"), 1); assert_eq!(delims.values_of("option").unwrap().collect::<Vec<_>>(), ["val1", "val2", "val3"]);
The next example shows the difference when turning delimiters off.
let nodelims = App::new("nodelims") .arg(Arg::with_name("option") .long("option") .use_delimiter(false) .takes_value(true)) .get_matches_from(vec![ "nodelims", "--option=val1,val2,val3", ]); assert!(nodelims.is_present("option")); assert_eq!(nodelims.occurrences_of("option"), 1); assert_eq!(nodelims.value_of("option").unwrap(), "val1,val2,val3");
fn value_delimiter(self, d: &str) -> Self
Specifies the separator to use when values are clumped together, defaults to ,
(comma).
NOTE: implicitly sets Arg::use_delimiter(true)
NOTE: implicitly sets Arg::takes_value(true)
Examples
let app = App::new("fake") .arg(Arg::with_name("config") .short("c") .long("config") .value_delimiter(";")); let m = app.get_matches_from(vec![ "fake", "--config=val1;val2;val3" ]); assert_eq!(m.values_of("config").unwrap().collect::<Vec<_>>(), ["val1", "val2", "val3"])
fn value_names(self, names: &[&'b str]) -> Self
Specifies names for values of option arguments. These names are cosmetic only, used for
help and usage strings only. The names are not used to access arguments. The values of
the arguments are accessed in numeric order (i.e. if you specify two names one
and two
one
will be the first matched value, two
will be the second).
NOTE: This implicitly sets .number_of_values()
if the number of value names is
greater than one. I.e. be aware that the number of "names" you set for the values, will be
the exact number of values required to satisfy this argument
NOTE: implicitly sets Arg::takes_value(true)
NOTE: Does not require or imply .multiple(true)
.
Examples
Arg::with_name("speed") .short("s") .value_names(&["fast", "slow"])
fn value_name(self, name: &'b str) -> Self
Specifies the name for value of option or positional arguments inside of help documenation. This name is cosmetic only, the name is not used to access arguments.
NOTE: implicitly sets Arg::takes_value(true)
Examples
Arg::with_name("input") .index(1) .value_name("FILE")
fn is_set(&self, s: ArgSettings) -> bool
Checks if one of the ArgSettings
settings is set for the argument
fn set(self, s: ArgSettings) -> Self
Sets one of the ArgSettings
settings for the argument
fn unset(self, s: ArgSettings) -> Self
Unsets one of the ArgSettings
settings for the argument