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crates.io · #36 most downloaded on crates.io
A simple to use, efficient, and full-featured Command Line Argument Parser
Last release 18 days ago
14 Sep 2026
Release timing varies
gaps range from 8 days to 3 months
Nearly every release is documented
notes for 56 of the last 60 stable releases
92 versions withdrawn
withdrawn after publishing
12 years old
462 releases · first in 2015
Low Index Multiples: fixes a bug where using low index multiples was propagated to subcommands (33924e88, closes #725)
One column per quarter.
Error Output: conflicting errors are now symmetrical, meaning more consistent and less confusing (3d37001d, closes #718)
Derive display order after propagation (9cb6facf, closes #706)
Fish Completions: fixes a bug where single quotes are not escaped (780b4a18, closes #704)
Help Message: fixes a regression bug where args with multiple(true) threw off alignment (ebddac79, closes #702)
Completions: adds ZSH completion support (3e36b0ba, closes #699)
AppSettings: adds new setting AppSettings::AllowNegativeNumbers (ab064546, closes #696)
with_defaults: Deprecate App::with_defaults() (26085409, closes #638)
arg_aliases: Ability to alias arguments (33b5f6ef, closes #669)
updates README.md with new website information and updated video tutorials info
Help Wrapping: fixes a regression-bug where the old {n} newline char stopped working (92ac353b, closes #661)
Help: adds ability to hide the possible values on a per argument basis (9151ef73, closes #640)
'{n}' to insert newlines in help text (c5a2b352)Help Wrapping: removes the verbage about using '{n}' to insert newlines in help text
Help Wrapping: makes some minor changes to when next line help is automatically used
Settings: fixes an issue where settings weren't propagated down through grandchild subcommands (b3efc107, closes #638)
Groups: fixes some usage strings that contain both args in groups and ones that conflict with each other (3d782def, closes #616)
Help Wrapping: fixes a bug where help is wrapped incorrectly and causing a panic with some non-English characters (d0b442c7, closes #626)
Help: adds new short hand way to use source formatting and ignore term width in help messages (7dfdaf20, closes #625)
fixes a bug where the help is printed twice (a643fb28, closes #623)
Help Subcommand: fixes misleading usage string when using multi-level subcommmands (e203515e, closes #618)
Completions: one can generate a basic fish completions script at compile time
Nothing published for this version
Nothing published for this version
Nothing published for this version
fixes some errors in the completion docs
Arg: adds new setting Arg::require_delimiter which requires val delimiter to parse multiple values
options with multiple values and using delimiters no longer parse additional values after a trailing space
ArgGroup: vastly improves ArgGroup docs by adding better examples (9e5f4f5d, closes #534)
removes extra newline from help output
App::before_help and App::after_help now correctly wrap (1f4da767, closes #516)removes extra newline from help output
Subcommand Aliases: fixes lifetime issue when setting multiple aliases at once
SubCommand Aliases: adds feature to yaml configs too
now properly dedups args that are also in groups (3ca0947c, closes #498)
Nothing published for this version
Nothing published for this version
Help: adds support for displaying info before help message
macros.rs: Added write_nspaces macro (a new version of write_spaces)
Arg Groups: fixes bug where arg name isn't printed properly (3019a685, closes #476)
Empty Values: fixes bug where empty values weren't stored (885d166f, closes #470)
fixes compiling with debug cargo feature
Help Subcommand: fixes issue where help and version flags weren't properly displayed (205b07bf, closes #466)
Help Message: fixes bug with wrapping in the middle of a unicode sequence (05365ddc, closes #456)
Nothing published for this version
Help Message: can auto wrap and aligning help text to term width (e36af026, closes #428)
Nightly: fixes failing nightly build (d752c170, closes #434)
AppSettings: clarifies that AppSettings do not propagate (3c8db0e9, closes #429)
Default Values: adds support for default values in args (73211952, closes #418)
Positional Arguments: now displays value name if appropriate (f0a99916, closes #420)
Multiple Values: fixes bug where number_of_values wasn't respected
adds support for building ArgGroups from standalone YAML
values: adds support for up to u64::max values per arg
arg_enum: enum declared with arg_enum returns [&'static str; #] instead of Vec
fixes cargo features to NOT require nightly with unstable features (dcbcc60c, closes #402)
There is now a priority of order to determine the name - This is perhaps the biggest breaking change. See the documentation for full details. Prior to…
App<'a, 'b, 'c, 'd, 'e, 'f> => App<'a, 'b>Arg<'a, 'b, 'c, 'd, 'e, 'f> => Arg<'a, 'b>ArgMatches<'a, 'b> => ArgMatches<'a>App::arg_group => App::groupApp::arg_groups => App::groupsArgGroup::add => ArgGroup::argArgGroup::add_all => ArgGroup::argsClapError => ErrorClapError::error_type => Error::kindClapResult => ResultClapErrorType => ErrorKindApp::subcommands_negate_reqsApp::subcommand_requiredApp::arg_required_else_helpApp::global_version(bool)App::versionless_subcommandsApp::unified_help_messagesApp::wait_on_errorApp::subcommand_required_else_helpSubCommand::newApp::error_on_no_subcommandArg::newArg::mutually_excludesArg::mutually_excludes_allArg::mutually_overrides_withsimple_enum!InvalidUnicode => InvalidUtf8InvalidArgument => UnknownArgument-o, --option <FILE> <FILE2> 'some option which takes two files'ArgMatches::values_of returns an Values now which implements Iterator (should not break any code)crate_version! returns &'static str instead of Stringclap_app! macro requires compiling with the unstable feature because the syntax could change slightly in the futureNothing published for this version
fixes an issue where invalid short args didn't cause an error
17_yaml: conditinonally compile 17_yaml example
Errors: fixes some instances when errors are missing a final newline
Errors: fixes a compiling bug when built on Windows or without the color feature
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