macro_rules! arg {
( $name:ident: $($tail:tt)+ ) => { ... };
( $($tail:tt)+ ) => { ... };
}
Expand description
Create an Arg
from a usage string.
Allows creation of basic settings for the Arg
.
NOTE: Not all settings may be set using the usage string method. Some properties are only available via the builder pattern.
Syntax
Usage strings typically following the form:
[explicit name] [short] [long] [value names] [...] [help string]
Explicit Name
The name may be either a bare-word or a string, followed by a :
, like name:
or
"name":
.
Note: This is an optional field, if it’s omitted the argument will use one of the additional fields as the name using the following priority order:
- Explicit Name
- Long
- Value Name
See Arg::name
.
Short
A short flag is a -
followed by either a bare-character or quoted character, like -f
or
-'f'
.
See Arg::short
.
Long
A long flag is a --
followed by either a bare-word or a string, like --foo
or
--"foo"
.
See Arg::long
.
Values (Value Notation)
This is set by placing bare-word between:
[]
like[FOO]
- Positional argument: optional
- Named argument: optional value
<>
like<FOO>
: required
See Arg::value_name
.
...
...
(three consecutive dots/periods) specifies that this argument may occur multiple
times (not to be confused with multiple values per occurrence).
See Arg::multiple_occurrences
.
Help String
The help string is denoted between a pair of double quotes ""
and may contain any
characters.
Examples
Command::new("prog")
.args(&[
arg!(--config <FILE> "a required file for the configuration and no short"),
arg!(-d --debug ... "turns on debugging information and allows multiples"),
arg!([input] "an optional input file to use")
])