Linux bash 中波浪号的含义（不是主目录）
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Meaning of tilde in Linux bash (not home directory)
提问by jbu
First off, I know that ~/is the home directory. CDing to ~or ~/takes me to the home directory.
首先，我知道那~/是主目录。CDing 到~或~/带我到主目录。
However, cd ~Xtakes me to a special place, where Xseems to be anything.
然而，cd ~X把我带到了一个特殊的地方，那里X似乎什么都没有。
In bash, if I hit "cd ~" and hit tab, it shows a bunch of possible ~Xoptions like ~mailand ~postgresand ~ssh. Going to those folders and doing a pwdshows me that these folders are not in the home directory; they're all over the place.
在 bash 中，如果我点击“ cd ~”并点击 Tab，它会显示一堆可能的~X选项，比如~mailand~postgres和~ssh。转到这些文件夹并执行 apwd显示这些文件夹不在主目录中；他们到处都是。
They are not aliases. I've checked.
They're not env.variables, or else they'd require a $.
它们不是别名。我查过了。它们不是env.变量，否则它们需要一个$.
What is setting these links, and where can I find where these are being set?
什么是设置这些链接，我在哪里可以找到这些链接的设置位置？
回答by Sean Bright
Are they the home directories of users in /etc/passwd? Services like postgres, sendmail, apache, etc., create system users that have home directories just like normal users.
他们是用户的主目录/etc/passwd吗？postgres、sendmail、apache 等服务会像普通用户一样创建具有主目录的系统用户。
回答by Ana Betts
Those are the home directories of the users. Try cd ~(your username), for example.
这些是用户的主目录。试试cd ~(your username)，例如。
回答by Joakim Elofsson
Those are users. Check your /etc/passwd.
那些是用户。检查您的/etc/passwd.
cd ~usernametakes you to that user's home directory.
cd ~username将您带到该用户的主目录。
回答by Jonathan Leffler
On my machine, because of the way I have things set up, doing:
在我的机器上，由于我设置的方式，执行以下操作：
cd ~ # /work1/jleffler
cd ~jleffler # /u/jleffler
The first pays attention to the value of environment variable $HOME; I deliberately set my $HOMEto a local file system instead of an NFS-mounted file system. The second reads from the password file (approximately; NIS complicates things a bit) and finds that the password file says my home directory is /u/jlefflerand changes to that directory.
第一个注意环境变量的值$HOME；我特意将 my 设置$HOME为本地文件系统而不是 NFS 挂载的文件系统。第二个从密码文件中读取（大约；NIS 使事情复杂化了一点）并发现密码文件说我的主目录是/u/jleffler并更改为该目录。
The annoying stuff is that most software behaves as above (and the POSIX specification for the shell requires this behaviour). I use some software (and I don't have much choice about using it) that treats the information from the password file as the current value of $HOME, which is wrong.
令人讨厌的是，大多数软件的行为都如上（并且 shell 的 POSIX 规范要求这种行为）。我使用了一些软件（我没有太多使用它的选择）将密码文件中的信息视为 $HOME 的当前值，这是错误的。
Applying this to the question - as others have pointed out, 'cd ~x' goes to the home directory of user 'x', and more generally, whenever tilde expansion is done, ~xmeans the home directory of user 'x' (and it is an error if user 'x' does not exist).
将此应用于问题 - 正如其他人指出的那样，“ cd ~x”转到用户“x”的主目录，更一般地说，每当完成波浪号扩展时，都~x意味着用户“x”的主目录（这是一个错误如果用户“x”不存在）。
It might be worth mentioning that:
可能值得一提的是：
cd ~- # Change to previous directory ($OLDPWD)
cd ~+ # Change to current directory ($PWD)
I can't immediately find a use for '~+', unless you do some weird stuff with moving symlinks in the path leading to the current directory.
我无法立即找到 ' ~+'的用途，除非您在通向当前目录的路径中移动符号链接来做一些奇怪的事情。
You can also do:
你也可以这样做：
cd -
That means the same as ~-.
这意味着与~-.
回答by TheBonsai
Tilde expansion in Bash:
Bash 中的波浪号扩展：
http://bash-hackers.org/wiki/doku.php/syntax/expansion/tilde
http://bash-hackers.org/wiki/doku.php/syntax/expansion/tilde
回答by tylerl
It's a Bash feature called "tilde expansion". It's a function of the shell, not the OS. You'll get different behavior with csh, for example.
这是一个名为“波浪号扩展”的 Bash 功能。这是外壳的功能，而不是操作系统。例如，使用 csh 会得到不同的行为。
To answer your question about where the information comes from: your home directory comes from the variable $HOME(no matter what you store there), while other user's homes are retrieved real-time using getpwent(). This function is usually controlled by NSS; so by default values are pulled out of /etc/passwd, though it can be configured to retrieve the information using any source desired, such as NIS, LDAP or an SQL database.
回答有关信息来自何处的问题：您的主目录来自变量$HOME（无论您在那里存储什么），而其他用户的主目录使用getpwent(). 该功能通常由NSS控制；因此，默认情况下会从 中提取值/etc/passwd，但可以将其配置为使用所需的任何来源（例如 NIS、LDAP 或 SQL 数据库）检索信息。
Tilde expansion is more than home directory lookup. Here's a summary:
波浪号扩展不仅仅是主目录查找。这是一个总结：
~ $HOME
~fred (freds home dir)
~+ $PWD (same effect as ./)
~- $OLDPWD (your previous directory)
~1 `dirs +1`
~2 `dirs +2`
~-1 `dirs -1`
dirsand ~1, ~-1, etc., are used in conjunction with pushdand popd.
dirs和~1、~-1等与pushd和结合使用popd。
回答by mgalgs
If you're using autofsthen the expansion might actually be coming from /etc/auto.home(or similar for your distro). For example, my /etc/auto.masterlooks like:
如果您正在使用，autofs那么扩展实际上可能来自/etc/auto.home（或类似于您的发行版）。例如，我的/etc/auto.master样子：
/home2 auto.home --timeout 60
and /etc/auto.homelooks like:
和/etc/auto.home看起来像：
mgalgs -rw,noquota,intr space:/space/mgalgs
回答by JS.
It's possible you're seeing OpenDirectory/ActiveDirectory/LDAP users "automounted" into your home directory.
您可能会看到 OpenDirectory/ActiveDirectory/LDAP 用户“自动挂载”到您的主目录中。
In *nix, ~will resolve to your home directory. Likewise ~Xwill resolve to 'user X'.
在 *nix 中，~将解析到您的主目录。同样~X将解析为“用户 X”。
Similar to automount for directories, OpenDirectory/ActiveDirectory/LDAP is used in larger/corporate environments to automount user directories. These users may be actual people or they can be machine accounts created to provide various features.
与目录的自动挂载类似，OpenDirectory/ActiveDirectory/LDAP 用于大型/公司环境以自动挂载用户目录。这些用户可能是真实的人，也可能是为提供各种功能而创建的机器帐户。
If you type ~Tabyou'll see a list of the users on your machine.
如果您键入，~Tab您将看到您机器上的用户列表。
