What directory is '~' when I type 'cd

问题:

I'm only new to using SSH, but when I log in I end up in the directory ~, which in general is the same directory when FTPing in. I can still go to /, but I don't know what the ~ means. Home? Where is it in relation to /, or how could I find out?

回答1:

~ is an alias to the currently logged in users home directory. To find out where that really is, type pwd (stands for: Print Working Directory) right after logging in, which should give you the location relative to /. It's probably something like:

/home/myusername

回答2:

~ is your home directory, yes. Which is very nice since your home directory is not always where you think it should be (/home/).

Also, fun fact: You can use "cd ~myuser" to get to the home directory of the user "myuser".

回答3:

As others have commented, the tilde indicates your current $HOME directory. This may or may not be the same as the value of ~username for your user name. On my machine, $HOME and ~ both refer to /work1/jleffler. However, ~jleffler is a reference to an NFS mounted directory, /u/jleffler, as specified in the /etc/passwd file (or any equivalent database - the POSIX standard defines the behaviour in terms of the getpwnam() function; see below). My profile carefully sets $HOME. It is interesting (aka exasperating) to work out which software packages use the wrong definition of the home directory.

For most people, ~ and ~username are the same for their user name, but that is not required. Given that you are asking the question, it is almost certainly the case that ~ and ~username are the same.

Quote from section 2.6.1 'Tilde Expansion' of POSIX.1-2008:

A "tilde-prefix" consists of an unquoted <tilde> character at the beginning of a word, followed by all of the characters preceding the first unquoted <slash> in the word, or all the characters in the word if there is no <slash>. [...] If the login name is null (that is, the tilde-prefix contains only the tilde), the tilde-prefix is replaced by the value of the variable HOME. If HOME is unset, the results are unspecified. Otherwise, the tilde-prefix shall be replaced by a pathname of the initial working directory associated with the login name obtained using the getpwnam() function [...]. If the system does not recognize the login name, the results are undefined.

回答4:

You can try realpath

realpath ~

回答5:

Yes, it is the home directory of the user you logged in as. You can use the command pwd (print working directory) to see where it is located on the file system.

回答6:

~ expands to your home directory, as has been pointed out, but I think it's worth noting that isn't a feature of ssh itself.

ssh (among many other wonderful features!) lets you establish a remote shell, and this shell can provided by many different pieces of software.

On a *nix system, your account will be associated with a particular shell, GNU bash is a popular choice. And it so happens than in bash, and most other POSIX compliant shells, the tilde character expands as a shortcut to your home directory.

回答7:

/ is the root of the file system ~/ or ~ is the root of your profile, ~/ is always /home/username

回答8:

Different shells may or may not handle this differently, but Johnathan got the closest without coming out and saying it. The shell expands "~" to whatever's stored in the $HOME environment variable. The shell expands ~username to whatever's listed in the shell field of /etc/passwd for the given username. If you don't override it, the shell (or ssh, depending on the implementation) will set $HOME to be the home field from /etc/passwd, so they're both the same (assuming you're "username") until you change one.

As to why you see a ~ in ssh...

The prompt says "~" is your current directory most likely because you're using Bash as your shell, and the value of $PS1 (the prompt string you see - it's set in /etc/profile or /etc/profile.d/*, more than likely) contains a \w or a \W somewhere. The \w string in the prompt shows the current directory, and collapses to a "~" when you're in the directory specified by $HOME. Here's a little demo starting in my homedir - note how the "\w" gets replaced with either the current directory or with a ~, based on what the value of HOME is set to. Also note that the trailing slash doesn't work - HOME can't end with a slash for this to work. :)

danny@machine ~ > export PS1='\w > '     # change my prompt (effective on next line)
~ > cd /tmp                              # move to /tmp to demonstrate
/tmp > export HOME=/tmp/                 # set HOME to include trailing /
/tmp > export HOME=/tmp                  # try again without trailing /
~ >                                      # notice that this works
~ > cd /home/danny                       # back to homedir
/home/danny > export HOME=/home/danny    # see how it's /home/danny, not ~
~ > export PS1='danny@machine \w > '     # after resetting $HOME, it should work ok
danny@machine ~ >                        # hooray!

回答9:

~ is your home directory. To see the path type:

echo ~

in the terminal

回答10:

And home, in relation to /, isn't necessarily always in the same place. That's why the ~ shortcut is so useful. The path to home should be in $HOME. Try typing

echo $HOME

回答11:

Home directory need not necessarily be under /home as kigurai has pointed out.