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string-replace - replace substrings
===================================
Synopsis
--------
.. BEGIN SYNOPSIS
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
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.. synopsis ::
string replace [-a | --all] [-f | --filter] [-i | --ignore-case]
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[-r | --regex] [(-m | --max-matches) MAX] [-q | --quiet]
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PATTERN REPLACEMENT [STRING ...]
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.. END SYNOPSIS
Description
-----------
.. BEGIN DESCRIPTION
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`` string replace `` is similar to `` string match `` but replaces non-overlapping matching substrings with a replacement string and prints the result. By default, *PATTERN* is treated as a literal substring to be matched.
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If **-r** or **--regex** is given, *PATTERN* is interpreted as a Perl-compatible regular expression, and *REPLACEMENT* can contain C-style escape sequences like **\t** as well as references to capturing groups by number or name as *$n* or *${n}* .
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If you specify the **-f** or **--filter** flag then each input string is printed only if a replacement was done. This is useful where you would otherwise use this idiom: `` a_cmd | string match pattern | string replace pattern new_pattern `` . You can instead just write `` a_cmd | string replace --filter pattern new_pattern `` .
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If **--max-matches MAX** or **-m MAX** is used, `` string replace `` will stop all processing after MAX lines of input have matched the specified pattern. In the event of `` --filter `` or `` -f `` , this means the output will be MAX lines in length. This can be used as an "early exit" optimization when processing long inputs but expecting a limited and fixed number of outputs that might be found considerably before the input stream has been exhausted.
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Exit status: 0 if at least one replacement was performed, or 1 otherwise.
.. END DESCRIPTION
Examples
--------
.. BEGIN EXAMPLES
Replace Literal Examples
^^^^^^^^^^^^^^^^^^^^^^^^
::
>_ string replace is was 'blue is my favorite'
blue was my favorite
>_ string replace 3rd last 1st 2nd 3rd
1st
2nd
last
>_ string replace -a ' ' _ 'spaces to underscores'
spaces_to_underscores
Replace Regex Examples
^^^^^^^^^^^^^^^^^^^^^^
::
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>_ string replace -r -a '[^\d.]+' ' ' '0 one two 3.14 four 5x'
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0 3.14 5
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>_ string replace -r '(\w+)\s+(\w+)' '$2 $1 $$' 'left right'
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right left $
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>_ string replace -r '\s*newline\s* ' '\n' 'put a newline here'
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put a
here
.. END EXAMPLES