31.11. Finding (Anyone's) Home Directory, Quickly
Most shells have a shortcut for the pathname to your home directory: a tilde (~), often called "twiddle" by Unix-heads. You can use ~ in a pathname to the home directory from wherever you are. For example, from any directory, you can list your home directory or edit your .cshrc file in it by typing:
% ls ~ ... % vi ~/.cshrc
You could change your current directory to your home directory by typing cd ~ or cd $HOME, but all shells have a shorter shortcut: typing plain cd with no argument also takes you home.
If your shell understands the tilde, it should also have an abbreviation for other users' home directories: a tilde with the username on the end. For example, the home directory for mandi, which might really be /remote/users/m/a/mandi, could be abbreviated ~mandi. On your account, if Mandi told you to copy the file named menu.c from her src directory, you could type:
% cp ~mandi/src/menu.c .
Don't confuse this with filenames like report~. Some programs, like the GNU Emacs (Section 19.4) editor and vi, may create temporary filenames that end with a ~ (tilde).
Your version of the Bourne shell might also emulate the special "directory" /u -- if your system administrator hasn't already set up /u, that is. It's a directory full of symbolic links (Section 10.4) to users' home directories. For instance, /u/jane could be a link to /home/users/jane. Many systems are now using /home for home directories, in favor of the old /usr/users or /u conventions. Darwin uses /Users/username (note the uppercase U!), but the tilde works the same there, too.
If all else fails, here's a trick that's probably too ugly to type a lot, but it's useful in Bourne shell scripts, where you don't want to "hardcode" users' home directory pathnames. This command calls the C shell to put mandi's home directory pathname into $dir:
username=mandi dir=`csh -fc "echo ~$username"`
In fact, using echo (Section 27.5) yourself is a good way to see how ~ works. Try echo ~, echo ~/xyz, echo ~xyz, and so on. Note that different shells do different things when ~user doesn't match any user: some print an error, others return the unmatched string.
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