#[non_exhaustive]
pub enum ArgAction {
Set,
Append,
StoreValue,
IncOccurrence,
SetTrue,
SetFalse,
Count,
Help,
Version,
}
Expand description
Behavior of arguments when they are encountered while parsing
Examples
let cmd = Command::new("mycmd")
.arg(
Arg::new("special-help")
.short('?')
.action(clap::ArgAction::Help)
);
// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
// New help available
let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
Variants (Non-exhaustive)§
This enum is marked as non-exhaustive
Set
When encountered, store the associated value(s) in ArgMatches
Examples
let cmd = Command::new("mycmd")
.arg(
Arg::new("flag")
.long("flag")
.action(clap::ArgAction::Set)
);
let matches = cmd.try_get_matches_from(["mycmd", "--flag", "value"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_many::<String>("flag").unwrap_or_default().map(|v| v.as_str()).collect::<Vec<_>>(),
vec!["value"]
);
Append
When encountered, store the associated value(s) in ArgMatches
Examples
let cmd = Command::new("mycmd")
.arg(
Arg::new("flag")
.long("flag")
.action(clap::ArgAction::Append)
);
let matches = cmd.try_get_matches_from(["mycmd", "--flag", "value1", "--flag", "value2"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_many::<String>("flag").unwrap_or_default().map(|v| v.as_str()).collect::<Vec<_>>(),
vec!["value1", "value2"]
);
StoreValue
Deprecated, replaced with ArgAction::Set
or ArgAction::Append
Builder: Instead of arg.action(ArgAction::StoreValue)
,
- Use
arg.action(ArgAction::Set)
for single-occurrence arguments - Use
arg.action(ArgAction::Append)
for multiple-occurrence arguments
Derive: opt-in to the new behavior with #[clap(action)]
IncOccurrence
Deprecated, replaced with ArgAction::SetTrue
or ArgAction::Count
SetTrue
When encountered, act as if "true"
was encountered on the command-line
If no default_value
is set, it will be false
.
No value is allowed. To optionally accept a value, see
Arg::default_missing_value
Examples
let cmd = Command::new("mycmd")
.arg(
Arg::new("flag")
.long("flag")
.action(clap::ArgAction::SetTrue)
);
let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_one::<bool>("flag").copied(),
Some(true)
);
let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_one::<bool>("flag").copied(),
Some(false)
);
SetFalse
When encountered, act as if "false"
was encountered on the command-line
If no default_value
is set, it will be true
.
No value is allowed. To optionally accept a value, see
Arg::default_missing_value
Examples
let cmd = Command::new("mycmd")
.arg(
Arg::new("flag")
.long("flag")
.action(clap::ArgAction::SetFalse)
);
let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_one::<bool>("flag").copied(),
Some(false)
);
let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_one::<bool>("flag").copied(),
Some(true)
);
Count
When encountered, increment a u8
counter
If no default_value
is set, it will be 0
.
No value is allowed. To optionally accept a value, see
Arg::default_missing_value
Examples
let cmd = Command::new("mycmd")
.arg(
Arg::new("flag")
.long("flag")
.action(clap::ArgAction::Count)
);
let matches = cmd.clone().try_get_matches_from(["mycmd", "--flag", "--flag"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_count("flag"),
2
);
let matches = cmd.try_get_matches_from(["mycmd"]).unwrap();
assert!(matches.contains_id("flag"));
assert_eq!(matches.occurrences_of("flag"), 0);
assert_eq!(
matches.get_count("flag"),
0
);
Help
When encountered, display Command::print_help
Depending on the flag, Command::print_long_help
may be shown
Examples
let cmd = Command::new("mycmd")
.arg(
Arg::new("special-help")
.short('?')
.action(clap::ArgAction::Help)
);
// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "-h"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
// New help available
let err = cmd.try_get_matches_from(["mycmd", "-?"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayHelp);
Version
When encountered, display Command::version
Depending on the flag, Command::long_version
may be shown
Examples
let cmd = Command::new("mycmd")
.version("1.0.0")
.arg(
Arg::new("special-version")
.long("special-version")
.action(clap::ArgAction::Version)
);
// Existing help still exists
let err = cmd.clone().try_get_matches_from(["mycmd", "--version"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayVersion);
// New help available
let err = cmd.try_get_matches_from(["mycmd", "--special-version"]).unwrap_err();
assert_eq!(err.kind(), clap::error::ErrorKind::DisplayVersion);
Implementations§
source§impl ArgAction
impl ArgAction
sourcepub fn takes_values(&self) -> bool
pub fn takes_values(&self) -> bool
Returns whether this action accepts values on the command-line
default_values
and env
may still be
processed.