Bash Prompt with Last Exit Code

Question

So, I\'ve been trying to customize by bash prompt so that it will look like

[feralin@localhost ~]$ _

with colors. I managed to get constant

Answer 1

To preserve original prompt format (not just colors), you could append following to the end of ~/.bashrc:

PS1_ORIG=$PS1 # original primary prompt value
PROMPT_COMMAND=__update_prompt # Func to be re-evaluated after each command is executed
__update_prompt() {
    local PREVIOUS_EXIT_CODE="$?"
    if [ $PREVIOUS_EXIT_CODE != 0 ]; then
        local RedCol='\[\e[0;31m\]'
        local ResetCol='\[\e[0m\]'
        local replacement="${RedCol}\u${ResetCol}"

        # Replace username color
        PS1=${PS1_ORIG//]\\u/]$replacement}
        ## Alternative: keep same colors, append exit code
        #PS1="$PS1_ORIG[${RedCol}error=$PREVIOUS_EXIT_CODE${ResetCol}]$ "
    else
        PS1=$PS1_ORIG
    fi
}

See also the comment about the alternative approach that preserves username color and just appends error code in red to the end of original prompt format