fish-shell/doc_src/cmds/eval.rst

.. _cmd-eval:

eval - evaluate the specified commands
======================================

Synopsis
--------

.. synopsis::

    eval [COMMANDS ...]

Description
-----------
**eval** evaluates the specified parameters as a command.
If more than one parameter is specified, all parameters will be joined using a space character as a separator.

If the command does not need access to stdin, consider using :doc:`source <source>` instead.

If no piping or other compound shell constructs are required, variable-expansion-as-command, as in  ``set cmd ls -la; $cmd``, is also an option.

Example
-------

The following code will call the ls command and truncate each filename to the first 12 characters.

::

    set cmd ls \| cut -c 1-12
    eval $cmd
docs: Add labels to all commands This allows us to use :ref: references, which don't require hardcoding it as html [ci skip] 2019-03-31 17:05:09 +08:00			`.. _cmd-eval:`

Switch command docs from \section to reStructuredText 2018-12-17 09:39:33 +08:00			`eval - evaluate the specified commands`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`======================================`
Switch command docs from \section to reStructuredText 2018-12-17 09:39:33 +08:00
Migrate the 'synopsis' sections to .rst format 2018-12-18 09:58:24 +08:00			`Synopsis`
			`--------`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
docs synopsis: add HTML highlighing and automate manpage markup Recent synopsis changes move from literal code blocks to [RST line blocks]. This does not translate well to HTML: it's not rendered in monospace, so aligment is lost. Additionally, we don't get syntax highlighting in HTML, which adds differences to our code samples which are highlighted. We hard-wrap synopsis lines (like code blocks). To align continuation lines in manpages we need [backslashes in weird places]. Combined with the *, , and `` markup, it's a bit hard to get the alignment right. Fix these by moving synopsis sources back to code blocks and compute HTML syntax highlighting and manpage markup with a custom Sphinx extension. The new Pygments lexer can tokenize a synopsis and assign the various highlighting roles, which closely matches fish's syntax highlighing: - command/keyword (dark blue) - parameter (light blue) - operator like and/or/not/&&/\|\| (cyan) - grammar metacharacter (black) For manpage output, we don't project the fish syntax highlighting but follow the markup convention in GNU's man(1): bold text type exactly as shown. italic text replace with appropriate argument. To make it easy to separate these two automatically, formalize that (italic) placeholders must be uppercase; while all lowercase text is interpreted literally (so rendered bold). This makes manpages more consistent, see string-join(1) and and(1). Implementation notes: Since we want manpage formatting but Sphinx's Pygments highlighing plugin does not support manpage output, add our custom "synopsis" directive. This directive parses differently when manpage output is specified. This means that the HTML and manpage build processes must not share a cache, because the parsed doctrees are cached. Work around this by using separate cache locations for build targets "sphinx-docs" (which creates HTML) and "sphinx-manpages". A better solution would be to only override Sphinx's ManualPageBuilder but that would take a bit more code (ideally we could override ManualPageWriter but Sphinx 4.3.2 doesn't really support that). --- Alternative solution: stick with line blocks but use roles like :command: or :option: (or custom ones). While this would make it possible to produce HTML that is consistent with code blocks (by adding a bit of CSS), the source would look uglier and is harder to maintain. (Let's say we want to add custom formatting to the [\|] metacharacters in HTML. This is much easier with the proposed patch.) --- [RST line blocks]: https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#line-blocks [backslashes in weird places]: https://github.com/fish-shell/fish-shell/pull/8626#discussion_r782837750 2022-01-09 22:09:46 +08:00			`.. synopsis::`

			`eval [COMMANDS ...]`
Migrate the 'synopsis' sections to .rst format 2018-12-18 09:58:24 +08:00
Convert \\subsection sections into rst format 2018-12-19 10:44:30 +08:00			`Description`
Fix command section separator line lengths 2019-01-03 12:10:47 +08:00			`-----------`
Commit doc_src progress. This is continuing the work I've been doing to remove the :: formatting for the synopsis sections of our manual pages. 2021-12-18 05:58:38 +08:00			`eval evaluates the specified parameters as a command.`
			`If more than one parameter is specified, all parameters will be joined using a space character as a separator.`
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
docs: Use :doc: role when linking to commands This makes it so we link to the very top of the document instead of a special anchor we manually include. So clicking e.g. :doc:`string <cmds/string>` will link you to cmds/string.html instead of cmds/string.html#cmd-string. I would love to have a way to say "this document from the root of the document path", but that doesn't appear to work, I tried `/cmds/string`. So we'll just have to use cmds/string in normal documents and plain `string` from other commands. 2022-09-24 01:57:49 +08:00			If the command does not need access to stdin, consider using :doc:`source <source>` instead.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
"eval" example to use $cmd as an array Signed-off-by: Osamu Aoki <osamu@debian.org> 2019-11-18 23:02:21 +08:00			If no piping or other compound shell constructs are required, variable-expansion-as-command, as in ``set cmd ls -la; $cmd``, is also an option.
Copy doc_src to sphinx_doc_src and add a TOC 2018-12-17 05:08:41 +08:00
Variables as commands are in fact supported, eval docs should not claim otherwise. (#5819) Provide an example that somewhat justifies eval's existence in light of this change. Also correct similar misinformation found in a comment. 2019-04-26 21:30:13 +08:00			`Example`
			`-------`
Switch \fish sections to rst format 2018-12-19 11:14:04 +08:00
Variables as commands are in fact supported, eval docs should not claim otherwise. (#5819) Provide an example that somewhat justifies eval's existence in light of this change. Also correct similar misinformation found in a comment. 2019-04-26 21:30:13 +08:00			`The following code will call the ls command and truncate each filename to the first 12 characters.`
Switch \fish sections to rst format 2018-12-19 11:14:04 +08:00
			`::`

Variables as commands are in fact supported, eval docs should not claim otherwise. (#5819) Provide an example that somewhat justifies eval's existence in light of this change. Also correct similar misinformation found in a comment. 2019-04-26 21:30:13 +08:00			`set cmd ls \\| cut -c 1-12`
Switch \fish sections to rst format 2018-12-19 11:14:04 +08:00			`eval $cmd`