How to check which terminal emulator is being currently used?

This function should do the job:

container() {
    pid=$$
    while true; do
        pid=$(ps -h -o ppid -p $pid 2>/dev/null)
        case $(ps -h -o comm -p $pid 2>/dev/null) in
        (gnome-terminal) echo "Running in gnome terminal";return;;
        (xterm) echo "Running in xterm";return;;
        (rxvt) echo "Running in rxvt";return;;
        (python) if [ ! -z "$(ps -h -o args -p $pid 2>/dev/null | grep guake)" ]; then echo "Running in Guake"; return; fi ;;
        esac
        [[ $(echo $pid) == 1 ]] && break
    done
}
container

Try this:

echo $TERM

This is more authoritative, but could be messed up by your programs. However on mine, it says xterm and on ttys it says linux, which I think stands for Linux Console.

You can get the terminal emulator name, by grepping the parents process name. Therefore it works with every terminal emulator.

In bash, zsh, etc.:

basename "/"$(ps -f -p $(cat /proc/$(echo $$)/stat | cut -d \  -f 4) | tail -1 | sed 's/^.* //')

With fish-shell:

basename "/"(ps -f -p (cat /proc/(echo %self)/stat | cut -d \  -f 4) | tail -1 | sed 's/^.* //')