bash $PATH 中 /usr/bin 和 /usr/local/bin 等的顺序
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Order of /usr/bin and /usr/local/bin and more in $PATH
提问by Bruce
On my Mac I used bash a lot. For my environment settings I added /usr/binand /usr/local/bininto $PATHas I normally did.
在我的 Mac 上，我经常使用 bash。对于我的环境设置，我像往常一样添加/usr/bin并/usr/local/bin进入$PATH。
While I do know what /usr/binand /usr/local/binare about, I am curious which should go before another, by convention? And is there a specific reason for that?
虽然我不知道什么是/usr/bin和/usr/local/bin是的，我很好奇这之前，另一个应该去，按照惯例？有什么具体原因吗？
Similar is for /usr/liband /usr/local/lib-- hopefully the answer is the same or similar.
相似是为了/usr/lib和/usr/local/lib——希望答案是相同或相似的。
a bit more -- Just an extension of the original question, how would you order the following in $PATH following the convention and why?
多一点 - 只是原始问题的扩展，您将如何按照约定在 $PATH 中订购以下内容，为什么？
/bin
/sbin
/usr/bin
/usr/sbin
/usr/local/bin
/usr/local/sbin
/opt/local/bin
/opt/local/sbin
回答by Asaph
/usr/binis where binaries supplied by the OS go. /usr/local/binis where user supplied binaries go. When you type the name of a command on the command line, the shell searches for said command in the paths contained in the $PATHenvironment variable in order. A common pattern is to have /usr/local/binprecede /usr/binin $PATH. This allows you to install alternate versions of binaries and have them gracefully "override" the binaries provided by the OS. And OS updates won't clobber your user installed packages. This pattern is notably used in OSX by the popular Homebrewpackage manager tool.
/usr/bin是操作系统提供的二进制文件所在的位置。/usr/local/bin是用户提供的二进制文件所在的位置。当您在命令行上键入命令的名称时，shell 会在$PATH环境变量中包含的路径中按顺序搜索该命令。一个常见的模式是有/usr/local/bin普瑞森/usr/bin在$PATH。这允许您安装二进制文件的替代版本，并让它们优雅地“覆盖”操作系统提供的二进制文件。并且操作系统更新不会破坏您的用户安装的软件包。流行的Homebrew包管理器工具在 OSX 中特别使用了这种模式。
For instance, at the time of this writing, OSX El Capitan supplies git version 2.5.4 (in /usr/bin). If you want a newer version, you can use Homebrew to install git version 2.7.0 (into /usr/local/bin). Since /usr/local/bincomes before /usr/binin the $PATHenvironment variable, when you issue the command gitin a shell, the newer Homebrew version will be used.
例如，在撰写本文时，OSX El Capitan 提供 git 版本 2.5.4（在 中/usr/bin）。如果你想要更新的版本，你可以使用 Homebrew 安装 git 版本 2.7.0（进入/usr/local/bin）。由于/usr/local/bin出现/usr/bin在$PATH环境变量之前，因此当您git在 shell 中发出命令时，将使用较新的 Homebrew 版本。
On fresh new Mac running OSX El Capitan (I happen to have one), the /etc/pathsfile contains the following:
在运行 OSX El Capitan 的全新 Mac 上（我碰巧有一台），该/etc/paths文件包含以下内容：
/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin
which produces the following $PATHenvironment variable:
它产生以下$PATH环境变量：
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
which is compatible with homebrew. I recommend sticking with this OSX default. If you really want to include /usr/local/sbin(listed in your question above), I would put it just before /usr/sbinfor similar reasons to above. As for /opt/local/binand /opt/local/sbin, I haven't personally found the need to add them to the path but it seems they might go in a similar spot as their /usr/localanalogs, since /opttraditionally contains user installed binaries.
这与自制软件兼容。我建议坚持使用这个 OSX 默认值。如果你真的想包括/usr/local/sbin（在你上面的问题中列出），我会把它放在前面/usr/sbin，原因与上面类似。至于/opt/local/binand /opt/local/sbin，我个人没有发现需要将它们添加到路径中，但似乎它们可能与它们的/usr/local类似物处于相似的位置，因为/opt传统上包含用户安装的二进制文件。
Note: The same explanation applies to /usr/libvs. /usr/local/lib.
注意：相同的解释适用于/usr/libvs. /usr/local/lib.
