bash中的＃：（hashtag/pound冒号）的用途

Question

我最近在查看Homebrew源代码。由于它是一种流行的工具，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（而且很难搜索符号，所以我找不到任何提及的符号）。这是一个公认的约定吗？它有特殊的意义吗？

Answer 1

它看起来是某种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，并记录下面的脚本。这是即使在Library/Homebrew/cmd/vendor-install.sh，其中类似的评论，可以发现这是标有@hide_from_man_page更加明显：

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

因此，据推测，这不是正是如此注释的所有片段，包括在手册页。

但是，您选择了一个不幸的示例，因为update被视为“基本命令”，因此记录在联机帮助页的单独部分中。让我们选择一个非基本的命令，比如style，您可以在Library/Homebrew/cmd/style.rb发现：

#: * `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，当你看看Library/Homebrew/manpages/brew.1.md.erb，你可以看到，他们是确实这得到手册页片段自动包含到主brew.1手册页：

# 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`. 

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

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

你可以看到生成的输出share/man/man1/brew.1：

.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脚本中可接受的约定，但是在各种语言和/或文档工具中使用了类似的约定。 JavaDoc（/**），Doxygen（/**,/*!,///,//!），JsDoc（/**）或C9（///）。