# kcli
**kcli** is a module that implements common routines used by command-line utilities, such as option parsing, usage display, and more.

## functions

### kcli_usage(kcli_set, kiochan)
kcli_usage() takes a `kcli_set` and prints a succinct usage summary to a [kiochan](../kio/kio.md).

## types

### struct kcli_set
`kcli_set` is a struct containing information about your program, such as its name, a synopsis of its function, a pointer to `argv`, and a list of `kcli_opt`s.

 * `const char* name` - program name (if null, will be determined from argv instead)
 * `size_t argc` - the number of arguments in the `argv` array.
 * `const char** argv` - the `argv` pointer passed to the `entry` function, representing the command-line arguments passed to the program.
 * `const char* desc` - program description
 * `const kcli_param* params` - a list of options expected by the program.
 * `size_t paramc` - the number of params in the list to process.
 * `const kcli_opt* opts` - a list of options expected by the program.
 * `size_t optc` - the number of options in the list to process.

a kcli_set might be used like so:

    #include <k/core.h>
    #include <k/io.h>
    #include <k/cli.h>
    u8 entry(kenv e) {
    	kcli_flag aardvark;
    	kcli_flag zebra;
    	char* user;
    	char* password;
		long age;
		kcli_param* params = {
    		{ "user", kcli_param_string, kcli_class_required,
    		  &user, "the user to log in as" }
			  // or Kcli_param(user,string,required,"the user to log in as"),

			{ "age", kcli_param_dec, kcli_class_optional,
    		  &age, "the age of the user" }
			  // or Kcli_param(age,dec,optional,"the age of the user"),
		};
    	kcli_opt* options = {
    		{ 'a', "aardvark", kcli_opt_flag, &aardvark,
    		  "a nocturnal burrowing mammal" },
			  // or Kcli_opt(aardvark, 'a', flag, "a nocturnal burrowing mammal")
    		{ 'z', "zebra", kcli_opt_flag, &zebra,
    		  "a striped equine" },
    		{ 'p', "password", kcli_opt_string, &password,
    		  "the password to log in with" }
    	};
    	kcli_set me = {
    		"demo", e.argc, e.argv,
    		"a demonstration of the kcli_set type",
			params, Kmsz(params),
			options, Kmsz(options)
    	},
		size_t args_parsed = kcli_parse(&me);
		if (args_parsed == 0) { kcli_usage(&me, e.err); return 1; }

		return 0;
	}

### struct kcli_opt
a `kcli_opt` is a representation of a command-line flag and its function. each option must have a unique `id` and/or a unique `name`.

 * `char id` - the short single-character form of the flag (or NUL for no short form)
 * `const char* name` - the long string form of the flag (or NULL for no long form)
 * `kcli_opt_kind kind` - enum that describes how the flag will function
 * `void* val` - a pointer to an appropriate type to store the return value in.
 * `const char* desc` - a description of the flag's purpose and function (or NULL for no description)

#### enum kcli_opt_kind

 * `kcli_opt_none` - flag is disabled and will not be shown in usage
 * `kcli_opt_string` - flag tells kcli to add a string to the list of expected parameters; appropriate string will be returned
 * `kcli_opt_oct` - flag tells kcli to add an octal number to the list of expected parameters
 * `kcli_opt_dec` - flag tells kcli to add a decimal number to the list of expected parameters
 * `kcli_opt_hex` - flag tells kcli to add a hexdecimal number to the list of expected parameters
 * `kcli_opt_flag` - flag is an option: will return `kcli_flag_on` if entered at least once, `kcli_flag_off` otherwise.
 * `kcli_opt_toggle` - flag toggles value on and off: will return `kcli_flag_on` if entered an odd number of times, `kcli_flag_off` otherwise.
 * `kcli_opt_accumulate` - flag increments a value every time it is entered; often used to implement `-v (--verbose)`-style options (e.g. `-vvvv` would return a value of `4`).

### struct kcli_param
`kcli_param` describes a parameter that may be passed to the program whether or not any flags are passed.

 * `const char* name` - a short name for the parameter
 * `kcli_param_kind kind` - the kind of parameter passed
 * `kcli_class class` - whether or not the parameter is optional
 * `void* val` - a pointer to an appropriate type of variable to fill
 * `const char* desc` - a description of the parameter's function

#### enum kcli_param_kind
 * `kcli_param_none` - parameter is disabled and will not be expected or accepted
 * `kcli_param_string` - parameter will not be parsed; a raw string will be returned
 * `kcli_param_oct` - parameter will be parsed as an octal number
 * `kcli_param_dec` - parameter will be parsed as a decimal number
 * `kcli_param_hex` - parameter will be parsed as a hexadecimal number

### enum kcli_class
 * `kcli_class_forbidden` - parameter may not be passed
 * `kcli_class_optional` - parameter may or may not be passed
 * `kcli_class_required` - parameter must be passed

### enum kcli_flag
results that an option of kind `kcli_opt_flag` can return.

 * `kcli_flag_off = 0` - flag is off
 * `kcli_flag_on = 1` - flag is on
 
## macros

### Kcli_param(field, kind, class, description)
a convenience macro for filling out parameter lists.

`Kcli_param(field,a,b,"description")` is transformed into:

    { "field", kcli_param_a, kcli_class_b, &field, "description" }

### Kcli_opt(field, kind, class, description)
a convenience macro for filling out option lists.

`Kcli_opt(name,'n',string,"description")` is transformed into:

    { 'n', "name", kcli_opt_string, &name, "description" }
