Features

The four steps

Every FLAP program follows the same four steps: initialise the CLI, define the arguments, parse, get the values.

program myprogram
use flap
implicit none
type(command_line_interface) :: cli
character(256)               :: outfile
integer                      :: error

call cli%init(progname='myprogram', description='Does something useful')              ! 1. initialise
call cli%add(switch='--output', switch_ab='-o', help='Output file', required=.true., &
             act='store', error=error)                                                 ! 2. define
call cli%parse(error=error)                                                            ! 3. parse
if (error /= 0) stop 1, quiet=.true.
call cli%get(switch='-o', val=outfile, error=error)                                    ! 4. get
endprogram myprogram

Feature map

Area	Features	Where
Arguments	named switches with abbreviations; positionals; flags (store_true/store_false) and flag pairs --x/--no-x; counters (-vvv); repeatable options (append); optional values (store*); hidden arguments; value placeholders (metavar)	Defining Arguments
Values	typed get into any integer, real, logical or character kind; fixed-size lists (nargs='N') and runtime-sized ones ('+', '*', get_varying); KEY=VALUE maps; inline values --opt=value; shell-like splitting of parse(args=...)	Arguments, Parsing
Sources	environment variables (explicit or generated names, comma-separated lists, flag words); INI configuration files; the source of every value (get_source, provenance); ignore_env for reproducible runs	Advanced
Validation	required options; choices (also case-insensitive); numeric ranges with open bounds or clamping; path checks (exist, readable, writable, -); mutually exclusive pairs, sets and commands; deprecated options and commands; application errors in FLAP's style (raise_error)	Arguments, Advanced, Errors
Commands	git-style commands, each with its options and help; aliases; option sets copied between commands; several commands per command line	Subcommands
Help and errors	help and usage generated from the definitions; "did you mean" suggestions; a hint line after an error; a shorter output after an error (usage_on_error); colours; case-insensitive switches and commands; alternate actions (--list-models)	Output, Errors
Generated files	man page (--man), Markdown (--markdown), completion scripts for bash, zsh, fish and PowerShell, printed or installed by the program itself (--show-completion, --install-completion)	Output Formats
Testing	parse a string (parse(args=...)), parse again (reset_parse), statuses returned instead of stopping (standalone=.false.), output units of your choice	Parsing, Errors
Menus	interactive numbered menus: single or multiple choice, defaults, yes/no questions, retries; safe in batch jobs	Interactive Menus

Every error and status has a named constant exported by the flap module (see Error Codes).

Module architecture

Use only the flap module: it exports the types, the error codes, the statuses and the source constants.

Any feature request is welcome: open an issue on GitHub.