bash PATH 中的冒号有什么作用
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What does the colon do in PATH
提问by Kabe Lee
I am new to bash, and I saw people often add :after a directory when modifying PATH. After searching for a while, I did not find an answer for that, or I believe I did not search it correctly. So I hope I could get an answer here.
我是 bash 新手，我看到人们:在修改PATH. 搜索了一段时间后，我没有找到答案，或者我相信我没有正确搜索它。所以我希望我能在这里得到答案。
Example:
例子：
/Users/chengluli/anaconda/bin:/Users/chengluli/.rbenv/shims:/
What does the :after binand shimsdo?
是什么在:以后bin和shims做？
回答by slashfoo
:is the separator. The PATHvariable is itself a list of folders that are "walked" through when you run a command.
:是分隔符。该PATH变量本身就是一个在您运行命令时“走过”的文件夹列表。
In this case, the folders on your PATHare:
在这种情况下，您的文件夹PATH是：
/Users/chengluli/anaconda/bin/Users/chengluli/.rbenv/shims/
/Users/chengluli/anaconda/bin/Users/chengluli/.rbenv/shims/
回答by cdarke
As others have said, the :is a separator (Windows uses a semi-colon ;). But you are probably thinking of a trailing colon :at the endof the PATHvariable. For example:
正如其他人所说，:is 是一个分隔符（Windows 使用分号;）。但你可能在想尾随冒号:在结束了的PATH变量。例如：
/Users/chengluli/anaconda/bin:/Users/chengluli/.rbenv/shims:
From the bash man pages:
从 bash 手册页：
A zero-length (null) directory name in the value of PATH indicates the current directory. A null directory name may appear as two adjacent colons, or as an initial or trailing colon.
PATH 值中的零长度（空）目录名称表示当前目录。空目录名称可能显示为两个相邻的冒号，或者显示为首字母或尾随冒号。
Putting the current directory in the PATH is generally considered a security risk and a bad idea. It is particularly dangerous when using the root user.
将当前目录放在 PATH 中通常被认为是一个安全风险和一个坏主意。使用 root 用户时尤其危险。
By the way, bash only uses $PATH on the first call of an external program, after that it uses a hash table. See man bashand the hashcommand
顺便说一下，bash 只在第一次调用外部程序时使用 $PATH，之后它使用哈希表。查看man bash和hash命令
回答by Huihoo
If you run ls -l 123at the command line, you are telling bash to find the command called lsin the filesystem. However, lsis just a file name, bash needs the absolute path of lsin the filesystem. So bash searches for a file called lsin a list of default directories, one by one in order.
如果您ls -l 123在命令行中运行，则是在告诉 bash 查找ls在文件系统中调用的命令。然而，ls只是一个文件名，bash需要ls文件系统中的绝对路径。因此 bash 会ls按顺序一个一个地搜索默认目录列表中调用的文件。
A list of default directories is stored in the PATHvariable, separated by :.
默认目录列表存储在PATH变量中，以:.
回答by gzh
Th quotation from output of man bashcommand
来自man bash命令输出的引用
PATH
The search path for commands. It is a colon-separated list of directories in which the shell looks for commands (see COMMAND EXECUTION below). A zero-length (null) directory name in the value of PATH indicates the current directory. A null directory name may appear as two adjacent colons, or as an initial or trailing colon. The default path is sys‐tem-dependent, and is set by the administrator who installs bash. A common value is ``/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin''.
PATH
命令的搜索路径。它是一个以冒号分隔的目录列表，shell 在其中查找命令（请参阅下面的命令执行）。PATH 值中的零长度（空）目录名称表示当前目录。空目录名称可能显示为两个相邻的冒号，或者显示为首字母或尾随冒号。默认路径依赖于系统，由安装 bash 的管理员设置。一个常见的值是“/usr/gnu/bin:/usr/local/bin:/usr/ucb:/bin:/usr/bin”。
If you have questions about bash script or environment variable, please use man bashfirstly.
如果您对 bash 脚本或环境变量有疑问，请先使用man bash。
