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docs: Reword quotes

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Also explain that `$(foo)` is also done in double-quotes.
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Fabian Boehm 2023-01-18 16:38:01 +01:00
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doc_src/language.rst
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@ -69,30 +69,31 @@ Here we define some of the terms used on this page and throughout the rest of th
Quotes
------
Sometimes features like :ref:`parameter expansion <expand>` and :ref:`character escapes <escapes>` get in the way. When that happens, you can use quotes, either single (``'``) or double (``"``). Between single quotes, fish performs no expansions. Between double quotes, fish only performs :ref:`variable expansion <expand-variable>`. No other kind of expansion (including :ref:`brace expansion <expand-brace>` or parameter expansion) is performed, and escape sequences (for example, ``\n``) are ignored. Within quotes, whitespace is not used to separate arguments, allowing quoted arguments to contain spaces.
Sometimes you want to give a command an argument that contains characters special to fish, like spaces or ``$`` or ``*``. To do that, you can use quotes::
rm "my file.txt"
to remove a file called ``my file.txt`` instead of trying to remove two files, ``my`` and ``file.txt``.
Fish understands two kinds of quotes: Single (``'``) and double (``"``), and both work slightly differently.
Between single quotes, fish performs no expansions. Between double quotes, fish only performs :ref:`variable expansion <expand-variable>` and :ref:`command substitution <expand-command-substitution>` in the ``$(command)``. No other kind of expansion (including :ref:`brace expansion <expand-brace>` or parameter expansion) is performed, and escape sequences (for example, ``\n``) are ignored. Within quotes, whitespace is not used to separate arguments, allowing quoted arguments to contain spaces.
The only meaningful escape sequences in single quotes are ``\'``, which escapes a single quote and ``\\``, which escapes the backslash symbol. The only meaningful escapes in double quotes are ``\"``, which escapes a double quote, ``\$``, which escapes a dollar character, ``\`` followed by a newline, which deletes the backslash and the newline, and ``\\``, which escapes the backslash symbol.
Single quotes have no special meaning within double quotes and vice versa.
Example::
rm "cumbersome filename.txt"
removes the file ``cumbersome filename.txt``, while
::
rm cumbersome filename.txt
removes two files, ``cumbersome`` and ``filename.txt``.
Another example::
More examples::
grep 'enabled)$' foo.txt
searches for lines ending in ``enabled)`` in ``foo.txt`` (the ``$`` is special to ``grep``: it matches the end of the line).
::
apt install "postgres-*"
installs all packages with a name starting with "postgres-", instead of looking through the current directory for files named "postgres-something".
.. _escapes:
Escaping Characters