Simplifying advanced Bash prompt variable (PS1) code

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 "
}