kakoune/doc/pages/command-parsing.asciidoc
2022-10-25 16:51:26 +11:00

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= Command Parsing
Kakoune commands, either loaded from a script or written in the command
prompt, are parsed according to the following rules:
== Basic parsing
- Commands are terminated by a `;` or an end of line.
- Words (command names and parameters) are delimited by whitespaces.
== Quoted Strings
If a word starts with `'`, `"`, or `%X` with `X` a _non-nestable_ punctuation
character (see <<command-parsing#balanced-strings,Balanced Strings>> below for
nestable characters), it is parsed as a quoted string whose delimiter is,
respectively, `'`, `"`, or `X`.
A quoted string contains every character (including whitespaces). Doubling
a closing delimiter escapes it. Thus, for example, entering two closing
delimiters at the end of a quoted string will render one of the characters
literally; that is, it will be considered as part of the quoted string's
content.
Inside double quotes, `%`-strings are processed unless the `%` is escaped by
doubling it. Double quotes inside these nested strings must also be escaped.
No other escaping takes place in quoted strings.
=== Quoted Strings Examples
- `'foo'` contains *foo*.
- `foo'bar'` is read verbatim, so it contains *foo'bar'*.
- `foo%|bar|` is read verbatim, so it contains *foo%|bar|*.
- `'foo''bar'` is a single word whose content is *foo'bar*.
- `"baz"""` is a single word whose content is *baz"*.
- `%|foo||bar|` is a single word whose content is *foo|bar*.
- `"foo %|""bar| %%,baz,"` is a single word whose content is *foo "bar %,baz,*.
== Balanced Strings
If a word starts with `%X` with `X` a _nestable_ punctuation character (one
of `(`, `[`, `{` and `<`), it is parsed as a balanced string whose closing
delimiter matches that of its opening delimiter (respectively, `)`, `]`,
`}`, and `>`).
There is no way to escape the opening and closing characters, even if they
are nested inside some other kind of string.
=== Balanced Strings Examples
- `%{foo}` contains *foo*.
- `%{foo\{bar}}` contains *foo\{bar}*.
- `foo%{bar}` contains *foo%{bar}*.
- `"foo %{bar}"` is a single word whose content is *foo bar*.
- `%{foo\{}` is a parse error, since the `{}` delimiters are not balanced.
- `%[foo\{]` contains *foo\{*, since it uses different delimiters.
== Non-Quoted words
Other words are non-quoted. Non-quoted words are terminated by either a
whitespace or a `;`.
If they start with a `\` followed by a `%`, `'`, or `"`, then that leading
`\` escapes those characters and is discarded.
If a whitespace or `;` is preceded by a `\`, then the `\` is discarded, and
the whitespace or `;` becomes part of the word. Any other `\` is treated
as a literal `\`.
== Typed Expansions
Quoted and Balanced strings starting with `%` might have an optional
alphabetic *expansion type* between the `%` and their delimiter (which is
always a punctuation character). This *expansion type* defines how the
string's content is going to be expanded. Rules for expanding and escaping
expansion types are the same as for `%`-strings.
- If the *expansion type* is empty, the string content is used verbatim.
- If the *expansion type* is one of `sh`, `reg`, `opt`, `val` or `arg`,
the string is expanded as described in <<expansions#,`:doc expansions`>>.
- For any other *expansion type*, a parsing error is raised.