How the PS1 of the title doesn't overwrite the PS1 of the prompt

Question

I noticed that in ~/.bashrc there are two sets of PS1 :

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$'
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h:\w\a\]$PS1"
    ;;
*)
    ;;
esac

The first one checks for $color_prompt , if it true or not and decides for the text of the prompt .
The second one checks for $TERM and decides for the title .

But both of them changes the same environment variable, so when the terminal starts and "see" that PS1 is set for the text of the prompt , how it can also set the title? Is ~/.bashrc being loaded twice?

Answer 1

The first condition sets $PS1 according to whether $color_prompt is enabled or not. The second assigned extends this by setting $PS1 to an expression the contains the previous value of $PS1

PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h:\w\a\]$PS1"
# Here ---------------------------------------------------^