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What are the most inscrutable lines of $SHELL you've ever written?

I'm sure some of you have absolute monstrosities of sigils (I know I do, in my .zshrc alone). Post them without context, and try and guess what other users's lines are. If you want to provide context or guess, use the markdown editor to spoiler-tag your guesses and explanations!

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  • I have this in my laptop's .bashrc

    PS1='\e[0m\n\e[40m[\e[32m\u\e[37m] [\e[31m\A \d\e[31m] [\e[33m`pwd`\e[37m]\e[K\n\e[K\n\e[1A'
PS0='\e[0m\n'
    hint

    some of the escape sequences move the cursor

    full explanation

    generates the prompt:

    
[username] [00:01 Thu Jan 1] [/home/username]
█

    with a slightly brighter/darker background (depending on terminal colors), while also resetting it to not effect the appearance of command outputs

    • \e[0m\n: new blank line
    • \e[40m: sets the background color for the prompt
    • [: literal text
    • \e[32m\u\e37m: username in green, reset color for brackets
    • ] [: literal text
    • \e[31m\A \d\e[31m: time/date in red, reset color
    • ] [: literal text
    • \e[33mpwd\e[37m: calls pwd, prints it in orange
    • ]: literal text
    • \e[K\n: fill the rest of the prompt line with the background
    • \e[K\n: fill the line where commands are typed with the background
    • \e[1A: move the cursor up so that it's in the background-filled area

    I am colorblind so I may have gotten colors wrong, but that's hardly where the interesting bit is.

    • That doesn't seem sensible. Moving the cursor will confuse bash and you can get the same effect by just omitting the last \n.

      Note that bash 5.0, but not earlier or later versions, is buggy with multiline prompts even if they're correct.

      Your colors should use 39 (or 49) for reset.

      Avoid doing external commands in subshells when there's a perfectly good prompt-expansion string that works.

      You seem to be generating several unnecessary blank lines, though I haven't analyzed them in depth; remember that doing them conditionally is an option, like I do:

      #PS1 built up incrementally before this, including things like setting TTY title for appropriate terminals
PS0='vvv \D{%F %T%z}\n'
PS1='^^^ \D{%F %T%z}\n'"$PS1"
prompt-command-exit-nonzero()
{
    # TODO map signal names and <sysexits.h> and 126/127 errors?
    # (128 also appears in some weird job-control cases; there are also
    # numerous cases where $? is not in $PIPESTATUS)
    # This has to come first since $? will be invalidated.
    # It's also one of the few cases where `*` is non-buggy for an array.
    local e=$? pipestatus="${PIPESTATUS[*]}"
    # Fixup newline. Note that interactive shells specifically use stderr
    # for the prompt, not stdin, stdout, or /dev/tty
    printf '\e[93;41m%%\e[39;49m%'"$((COLUMNS-1))"'s\r' >&2
    # if e or any pipestatus is nonzero
    if [[ -n "${e/0}${pipestatus//[ 0]}" ]]
    then
        if [[ "$pipestatus" != "$e" ]]
        then
            local pipestatus_no_SIGPIPE="${pipestatus//141 /}"
            local color=41
            if [[ -z "${pipestatus_no_SIGPIPE//[ 0]}" ]]
            then
                color=43
            fi
            printf '\e[%smexit_status: %s (%s)\e[49m\n' "$color" "$e" "${pipestatus// / | }" >&2
        else
            printf '\e[41mexit_status: %s\e[49m\n' "$e" >&2
        fi
    fi
}
PROMPT_COMMAND='prompt-command-exit-nonzero'
48 comments