Simplifying advanced Bash prompt variable (PS1) code - bash

Question

So I've found the following cool Bash prompt:
..with the very basic logic of:
PS1="\[\033[01;37m\]\$? \$(if [[ \$? == 0 ]]; then echo \"\[\033[01;32m\]\342\234\223\"; else echo \"\[\033[01;31m\]\342\234\227\"; fi) $(if [[ ${EUID} == 0 ]]; then echo '\[\033[01;31m\]\h'; else echo '\[\033[01;32m\]\u#\h'; fi)\[\033[01;34m\] \w \$\[\033[00m\] "
However, this is not very basic and happens to be an incredible mess. I'd like to make it more readable.
How?

Answer 1

Use PROMPT_COMMAND to build the value up in a sane fashion. This saves a lot of quoting and makes the text much more readable. Note that you can use \e instead of \033 to represent the escape character inside a prompt.
set_prompt () {
local last_command=$? # Must come first!
PS1=""
# Add a bright white exit status for the last command
PS1+='\[\e[01;37m\]$? '
# If it was successful, print a green check mark. Otherwise, print
# a red X.
if [[ $last_command == 0 ]]; then
PS1+='\[\e[01;32m\]\342\234\223 '
else
PS1+='\[\e[01;31m\]\342\234\227 '
fi
# If root, just print the host in red. Otherwise, print the current user
# and host in green.
# in
if [[ $EUID == 0 ]]; then
PS1+='\[\e[01;31m\]\h '
else
PS1+='\[\e[01;32m\]\u#\h '
fi
# Print the working directory and prompt marker in blue, and reset
# the text color to the default.
PS1+='\[\e[01;34m\] \w \$\[\e[00m\] '
}
PROMPT_COMMAND='set_prompt'
You can define variables for the more esoteric escape sequences, at the cost of needing some extra escapes inside the double quotes, to accommodate parameter expansion.
set_prompt () {
local last_command=$? # Must come first!
PS1=""
local blue='\[\e[01;34m\]'
local white='\[\e[01;37m\]'
local red='\[\e[01;31m\]'
local green='\[\e[01;32m\]'
local reset='\[\e[00m\]'
local fancyX='\342\234\227'
local checkmark='\342\234\223'
PS1+="$white\$? "
if [[ $last_command == 0 ]]; then
PS1+="$green$checkmark "
else
PS1+="$red$fancyX "
fi
if [[ $EUID == 0 ]]; then
PS1+="$red\\h "
else
PS1+="$green\\u#\\h "
fi
PS1+="$blue\\w \\\$$reset "
}