I was messing around with the color codes trying to understand how color code is used in bash script and I found that it works fine without including \[\] around it as in here:
This..
red="\033[38;5;203m"
export PS1="$red\u$green\$(__git_ps1)$blue \W"
..gives the same result as that:
red="\[\033[38;5;203m\]"
export PS1="$red\u$green\$(__git_ps1)$blue \W"
So is the second form necessary?
If your prompt contains non-printing characters
that are not enclosed in \[...\],
then the shell will miscalculate the width of the prompt.
As a result, it will be confused about where the cursor is,
and it will update the display erroneously.
A classic example of this occurs
if you type a command so long that it's longer than the window is wide,
so it wraps to the next line,
and then you backspace back up to the first line.
