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:ID:       46115263-ed3d-4acc-9ec5-523d7acf87b8
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#+TITLE: Commandline interface arguments processing
#+AUTHOR: Svjatoslav Agejenko
#+LANGUAGE: en

- [[id:bb4f96cd-458c-495b-a605-313b2e3e28d2][Back to CLI Helper - library main page]]

* Terminology
** Command and argument

Every command-line application has a way of receiving input from
users, usually in the form of command-line arguments. A command-line
argument is a piece of information provided to the command-line
application when it's invoked. These arguments are provided as an
array of strings. The first element of the array (argument 0) is
typically the name of the command itself.

In the example below, 'my-video-coder' is our command, and the rest
are arguments:

#+BEGIN_SRC shell
my-video-coder encode --input vid1.mp4 vid2.mp4 vid3.mp4 --quality 5
#+END_SRC

To better understand how these concepts work together, let's break
down our example command:

| argument # | value(s)                   | type                          |
|------------+----------------------------+-------------------------------|
|          0 | my-video-coder             | command                       |
|          1 | encode                     | [[id:94242e8a-c59b-42fd-8cc7-ba3df1938119][subcommand]]                    |
|          2 | --input                    | [[id:ffedf388-4d23-41eb-98d0-83fd3940b24d][option1]]                       |
|    3, 4, 5 | vid1.mp4 vid2.mp4 vid3.mp4 | [[id:8a39d20c-421f-4bc7-94e4-8e561e58bea0][parameters for --input option]] |
|          6 | --quality                  | [[id:ffedf388-4d23-41eb-98d0-83fd3940b24d][option2]]                       |
|          7 | 5                          | [[id:8a39d20c-421f-4bc7-94e4-8e561e58bea0][parameter for --quaily option]] |

** Subcommand
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Subcommands are arguments that invoke more specific action that a
command can perform. They are often used with commands that have
multiple functions. In our example, *encode* is a subcommand of
*my-video-coder*.

** Option
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Options are arguments that change the behavior of a command or
subcommand. They usually start with a dash (-) or double dash
(--). For instance, *--input* and *--quality* are options in our
example command.

** Parameter
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Parameter provides additional information to a command, subcommand or
option.

For instance, in our example:
- 'vid1.mp4 vid2.mp4 vid3.mp4' are parameters for the *--input* option.
- '5' is a parameter for the *--quality* option.