Bash/bash-completion

Installation

apt install bash-completion

Enable

1. Per User
2. Globally

Enable per user

edit ~/.bashrc

if ! shopt -oq posix; then
    if [ -f /usr/share/bash-completion/bash_completion ]; then
        . /usr/share/bash-completion/bash_completion
        elif [ -f /etc/bash_completion ]; then
            . /etc/bash_completion
        fi
    fi

• To try it without logging out and back in, run:

. ~/.bashrc

• Or open a new shell.
• Then try to use tab-completion
• That dot and space at the beginning (.) is the same as using the source keyword in bash, but is more portable.
• If you want it to work when su'd into the root account, do the same thing in root's home directory (typically /root).

Enable globally

• Do changes from (2.1) in /etc/bash.bashrc
• To anyone who's wondering why this works, the . in front of /etc/bash_completion does not refer to the current directory, since it has spaces around it.
• It instead makes the contents of the given file be evaluated in the currently running shell, instead of being executed in a new subshell. It is standardized here.
• In Bash, this . can be replaced by the command source, but this is not standardized by POSIX and is less portable so I tend to steer people away from using it.
• In this case, since it is specifically a program for extending bash, rather than something that needs to work in a bourne shell or ksh, you can feel free to substitute source for readability.
• Incidentally, this behavior (not opening a sub-shell) is similar to the way DOS/Windows .BAT scripts work normally, changing the state of the shell they are run in.
• This is why if you cd into a different path in a shell script, you won't be in that path when the script exits like you would be in a .BAT.