tilde
TLDR
Home directory
$ cd ~
Another user's home directory$ cd ~[username]
Previous directory$ cd ~-
Current directory$ echo ~+
Case modification (bash 4+)$ echo ${var~~}
SYNOPSIS
~
~username
~+
~-
DESCRIPTION
~ (tilde) is expanded by the shell to directory paths. It's a shorthand that avoids hardcoding paths like /home/user.
Tilde expansion only occurs at the start of a word or after :. In the middle of text, ~ is literal.
$ cd ~ # Go home
cd ~/Documents # Home subdirectory
cd ~root # Root's home
PATH=$PATH:~/bin # After : works
The ~+ and ~- forms mirror the pushd/popd directory stack, allowing quick navigation between recent directories.cd ~/Documents # Home subdirectory
cd ~root # Root's home
PATH=$PATH:~/bin # After : works
EXAMPLES
$ # Copy to home
cp file.txt ~
# Use another user's home
sudo cp config ~www-data/
# Toggle between directories
cd /var/log
cd /etc
cd ~- # Back to /var/log
cd ~- # Back to /etc
# Case toggle (bash 4+)
name="Hello"
echo ${name~~} # hELLO
cp file.txt ~
# Use another user's home
sudo cp config ~www-data/
# Toggle between directories
cd /var/log
cd /etc
cd ~- # Back to /var/log
cd ~- # Back to /etc
# Case toggle (bash 4+)
name="Hello"
echo ${name~~} # hELLO
TILDE EXPANSIONS
~
Current user's home directory ($HOME)~username
Specified user's home directory~+
Current working directory ($PWD)~-
Previous working directory ($OLDPWD)
PARAMETER EXPANSION (bash 4+)
${var^}
Uppercase first character${var^^}
Uppercase all characters${var,}
Lowercase first character${var,,}
Lowercase all characters${var~}
Toggle case of first character${var~~}
Toggle case of all characters
CAVEATS
Tilde only expands when unquoted and at word start. "~" is literal, not home.
~user looks up the user in the password database, not just string concatenation.
~- is empty if no previous directory (new shell).
