Getting a dynamic bash prompt PS1 right

Question

I'm working on a dynamic bash prompt where I want reported in PS1 which version of a config file is enabled on the local filesystem. This is a contrived example of what I'm trying to do, simplified. The things that are going wrong: bad wrapping and/or escape brackets appearing. Can anyone spot what I'm doing wrong?

If the contrived config matches "v2", I want to see that version in PS1 as YELLOW. If it's "v1", in the prompt as GREEN. The setup:

$ grep FOOVER foo-*.conf
foo-v1.conf:# FOOVER xyz-v1
foo-v2.conf:# FOOVER zet-v2

I'd then symlink foo.conf foo-v1.conf. My bashrc:

 0 GREEN=$(tput setaf 034)
 1 YELLOW=$(tput setaf 3)
 2 BLUE=$(tput setaf 4)
 3 CYAN=$(tput setaf 6)
 4 BOLD=$(tput bold)
 5 RESET=$(tput sgr0)
 6 CONF=$HOME/foo.conf
 7
 8 function __get_foo_version () {
 9   FOOVER=$(grep FOOVER $CONF | awk '{print $3}')
10   if [[ "$FOOVER" =~ v2$ ]]; then
11     style_foover="${BOLD}${YELLOW}$FOOVER"
12     #style_foover="\[${BOLD}${YELLOW}\]$FOOVER"
13   elif [[ "$FOOVER" =~ v1$ ]]; then
14     style_foover="${BOLD}${GREEN}$FOOVER"
15     #style_foover="\[${BOLD}${GREEN}\]$FOOVER"
16   fi
17   echo $style_foover
18 }
19
20 style_host="\[${RESET}${BLUE}\]"
21 style_path="\[${RESET}${CYAN}\]"
22 style_reset="\[${RESET}\]"
23
24 PS1='user@'
25 PS1+="${style_host}host"
26 PS1+="${style_reset} "
27 PS1+="\$(__get_foo_version) "
28 PS1+="${style_reset}"
29 PS1+="${style_path}\W"
30 PS1+="${style_reset} $ "

When I run the above, I get this behavior, which looks good at first: http://imgur.com/HIR3SoA

But when I up-arrow to a long command, the bad wrapping happens: http://imgur.com/qLfdUor

When I disable lines 11, 14 and enable lines 12, 15, I get the brackets that are intended to handle non-printing chars showing up in PS1:

(not enough reputation points to post more than 2 links :( imgur.com slash nkXFDyJ)

user@host \[\]xyz-v1 ~ $

.. and I still get the bad wrapping in this case.

Answer 1

Use \x01 (or \001) and \x02 (or \002) and then evaluate them with echo -e:

    function __get_foo_version () {
      FOOVER=$(grep FOOVER $CONF | awk '{print $3}')
      if [[ "$FOOVER" =~ v2$ ]]; then
        #style_foover="${BOLD}${YELLOW}$FOOVER"
>>>     style_foover="\x01${BOLD}${YELLOW}\x02$FOOVER"
      elif [[ "$FOOVER" =~ v1$ ]]; then
        #style_foover="${BOLD}${GREEN}$FOOVER"
>>>     style_foover="\x01${BOLD}${GREEN}\x02$FOOVER"
      fi
>>>   echo -e "$style_foover"
    }

A more complete answer as to why this fixes it is here: https://superuser.com/questions/301353/escape-non-printing-characters-in-a-function-for-a-bash-prompt