eshell-eval-using-options

eshell-eval-using-options is a Lisp macro in `esh-opt.el'.

(eshell-eval-using-options NAME MACRO-ARGS OPTIONS &rest BODY-FORMS)

Process NAME's MACRO-ARGS using a set of command line OPTIONS.
After doing so, stores settings in local symbols as declared by OPTIONS;
then evaluates BODY-FORMS -- assuming all was OK.

OPTIONS is a list, beginning with one or more elements of the form:
(SHORT LONG VALUE SYMBOL HELP-STRING)
Each of these elements represents a particular command-line switch.

SHORT is either nil, or a character that can be used as a switch -SHORT.
LONG is either nil, or a string that can be used as a switch --LONG.
At least one of SHORT and LONG must be non-nil.
VALUE is the value associated with the option. It can be either:
t - the option needs a value to be specified after the switch;
nil - the option is given the value t;
anything else - specifies the actual value for the option.
SYMBOL is either nil, or the name of the Lisp symbol that will be bound
to VALUE. A nil SYMBOL calls `eshell-show-usage', and so is appropriate
for a "--help" type option.
HELP-STRING is a documentation string for the option.

Any remaining elements of OPTIONS are :KEYWORD arguments. Some take
arguments, some do not. The recognized :KEYWORDS are:

:external STRING
STRING is an external command to run if there are unknown switches.

:usage STRING
STRING is the initial part of the command's documentation string.
It appears before the options are listed.

:post-usage STRING
STRING is an optional trailing part of the command's documentation string.
It appears after the options, but before the final part of the
documentation about the associated external command (if there is one).

:show-usage
If present, then show the usage message if the command is called with no
arguments.

:preserve-args
If present, do not pass MACRO-ARGS through `eshell-flatten-list'
and `eshell-stringify-list'.

For example, OPTIONS might look like:

'((?C nil nil multi-column "multi-column display")
(nil "help" nil nil "show this usage display")
(?r "reverse" nil reverse-list "reverse order while sorting")
:external "ls"
:usage "[OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically across.")

`eshell-eval-using-options' returns the value of the last form in
BODY-FORMS. If instead an external command is run (because of
an unknown option), the tag `eshell-external' will be thrown with
the new process for its value.

Lastly, any remaining arguments will be available in a locally
interned variable `args' (created using a `let' form).