bash prompt and echoing colors inside a function

\[ and \] must be used in $PS* directly, rather than just having them output via echo.

LIGHTGREEN="\033[1;32m"
LIGHTRED="\033[1;31m"
WHITE="\033[0;37m"
RESET="\033[0;00m"

function error_test {
    if [[ $? = "0" ]]; then
        echo -e "$LIGHTGREEN"
    else
        echo -e "$LIGHTRED"
    fi
}

PS1="\u\[\$(error_test)\]@\w\[$RESET\] \$ "

I found this topic looking for answer how to set bash color with escaping \[ \] from bash function.

Actually there is solution. Bash allows to generate PS1 prompt each time prompt is rendered.

set_bash_prompt(){
    PS1="\u@\h $(call_your_function) $>"
}

PROMPT_COMMAND=set_bash_prompt

This way, PS1 will be interpreted each time prompt will be displayed, so it will call function and render properly all escaping sequences including \[ \] which are important for counting length of prompt (e.g. to make command history work correctly).

Hopefully this will help someone, as I spend half a day to solve this issue.

Use \001 instead of \[ and \002 instead of \], and be aware of the consequences of usingPROMPT_COMMAND as that method will reset the prompt every single time (which can also be just what you want).

The solution for bash prompt echoing colors inside a function is explained here:

The \[ \] are only special when you assign PS1, if you print them inside a function that runs when the prompt is displayed it doesn't work. In this case you need to use the bytes \001 and \002

There is also this other answer that points in the same direction:

bash-specific \[ and \] are in fact translated to \001 and \002

Setting PS1 inside a function called by PROMPT_COMMAND as suggested in the accepted aswer resets PS1 every single time not allowing other scripts to easily modify your promtp (for example Python virtualnenv activate.sh):

$ echo $PS1
<your PS1>
$ PS1="(TEST)$PS1"
$ echo $PS1
<(TEST) is not prepended to PS1 if you are using PROMPT_COMMAND as it is reset>