#: (hashtag/磅冒号) in bash 的目的是什么

Question

我最近在查看 Homebrew 源代码。由于它是一种流行的工具，因此代码可能相对干净。我注意到他们使用#: 评论风格（例如：update.sh）。我在其他任何地方都没有看到过（而且很难搜索符号，所以我找不到任何提及它的内容）。这是公认的约定吗？有什么特殊含义吗？

Answer 1

它看起来像是联机帮助页的某种文档片段：它以标准联机帮助页样式编写，并记录了后面的脚本。这在Library/Homebrew/cmd/vendor-install.sh 中更加明显，可以找到类似的评论，并带有@hide_from_man_page 的标签：

#: @hide_from_man_page
#:  * `vendor-install` [<target>]:
#:     Install vendor version of Homebrew dependencies.

因此，据推测，所有未如此注释的片段都包含在手册页中。

不过，您选择了一个不幸的示例，因为 update 被认为是“基本命令”，因此记录在手册页的单独部分中。让我们选择一个非必要的命令，例如style，您可以在Library/Homebrew/cmd/style.rb 中找到它：

#:  * `style` [`--fix`] [`--display-cop-names`] [<formulae>|<files>]:
#:    Check formulae or files for conformance to Homebrew style guidelines.
#:
#:    <formulae> is a list of formula names.
#:
#:    <files> is a list of file names.
#:
#:    <formulae> and <files> may not be combined. If both are omitted, style will run
#:    style checks on the whole Homebrew `Library`, including core code and all
#:    formulae.
#:
#:    If `--fix` is passed and `HOMEBREW_DEVELOPER` is set, style violations
#:    will be automatically fixed using RuboCop's `--auto-correct` feature.
#:
#:    If `--display-cop-names` is passed, the RuboCop cop name for each violation
#:    is included in the output.
#:
#:    Exits with a non-zero status if any style violations are found.

现在，当您查看 Library/Homebrew/manpages/brew.1.md.erb 时，您会发现它们是确实手册页片段，它们会自动包含在主要的 brew.1 手册页中：

# To make changes to this man page:
#
# - For changes to a specific command (appears in the `COMMANDS` section):
#   - Edit the top comment in `Library/Homebrew/cmd/<command>.{rb,sh}`.
#   - Make sure to use the line prefix `#:` for the comments to be recognized as
#     documentation. If in doubt, compare with already documented commands.
# - For other changes: Edit this file.
#
# When done, regenerate the man page and its HTML version by running `brew man`.

还有here's the line where they get included into the manpage:

<%= commands.join("\n") %>

你可以在share/man/man1/brew.1看到生成的输出：

.TP
\fBstyle\fR [\fB\-\-fix\fR] [\fB\-\-display\-cop\-names\fR] [\fIformulae\fR|\fIfiles\fR]
Check formulae or files for conformance to Homebrew style guidelines\.
.
.IP
\fIformulae\fR is a list of formula names\.
.
.IP
\fIfiles\fR is a list of file names\.
.
.IP
\fIformulae\fR and \fIfiles\fR may not be combined\. If both are omitted, style will run style checks on the whole Homebrew \fBLibrary\fR, including core code and all formulae\.
.
.IP
If \fB\-\-fix\fR is passed and \fBHOMEBREW_DEVELOPER\fR is set, style violations will be automatically fixed using RuboCop\'s \fB\-\-auto\-correct\fR feature\.
.
.IP
If \fB\-\-display\-cop\-names\fR is passed, the RuboCop cop name for each violation is included in the output\.
.
.IP
Exits with a non\-zero status if any style violations are found\.
.

和share/doc/homebrew/brew.1.html:

<dt><code>style</code> [<code>--fix</code>] [<code>--display-cop-names</code>] [<var>formulae</var>|<var>files</var>]</dt><dd><p>Check formulae or files for conformance to Homebrew style guidelines.</p>

<p><var>formulae</var> is a list of formula names.</p>

<p><var>files</var> is a list of file names.</p>

<p><var>formulae</var> and <var>files</var> may not be combined. If both are omitted, style will run
style checks on the whole Homebrew <code>Library</code>, including core code and all
formulae.</p>

<p>If <code>--fix</code> is passed and <code>HOMEBREW_DEVELOPER</code> is set, style violations
will be automatically fixed using RuboCop's <code>--auto-correct</code> feature.</p>

<p>If <code>--display-cop-names</code> is passed, the RuboCop cop name for each violation
is included in the output.</p>

我不知道这是否是 shell 脚本中公认的约定，但类似的约定用于各种语言和/或文档工具，例如JavaDoc (/**)、Doxygen (/**、/*!、///、//!)、JsDoc (/**) 或 C♯ (///)。