How BASH Changes Terminal Window Title

In many distributions bash automatically changes the terminal title. I thought it was hardcoded in bash, but it turns out to be not. It is usually implemented with PROMPT_COMMAND.

Environment variable $PROMPT_COMMAND defines the command to be automatically executed before displaying the primary prompt (i.e. $PS1). It is set by a script that is sourced by interative instances of bash. In Gentoo it is in /etc/bash/bashrc:

case ${TERM} in
    xterm*|rxvt*|Eterm|aterm|kterm|gnome*|interix)
        PROMPT_COMMAND='echo -ne "\033]0;${USER}@${HOSTNAME%%.*}:${PWD/$HOME/~}\007"'
        ;;
    screen)
        PROMPT_COMMAND='echo -ne "\033_${USER}@${HOSTNAME%%.*}:${PWD/$HOME/~}\033\\"'
        ;;
esac

In fact, the first version above also works with newer versions of screen.