Bash prompt that won't clobber long commands

Question

I'm trying to set up a bash prompt for - hostname(screen#):directory$ which is coloured green if the last command completed successfully, red if not. This is what I have so far, which actually does the job but seems to cause display problems if the command wraps a line:

 PS1="\[\`if [[ \$? = "0" ]]; then echo '\e[32m'; else echo '\e[31m' ; fi\` - \h(${WINDOW}):\W$\e[00m "

Googling the issue I found this helpful SO post with a comment that mentions wrapping nonprinting characters in \\[ and \\] to avoid this issue. Therefore I tried the following, but it did not solve the issue, and furthermore breaks the colour change:

PS1="\[\`if [[ \$? = "0" ]]; then echo '\e[32m'; else echo '\e[31m' ; fi\`\] - \h(${WINDOW}):\W$\[\e[00m\] "

How can I keep the structure of this prompt, with colours, but fix it so that long commands are displayed properly?

Answer 1

I have a fancy prompt with colors, and now bash doesn't seem to know how wide my terminal is. Lines wrap around incorrectly.

---

I have another proper way to do this, put this code in your ~/.bashrc or create a new file and source file :

PROMPT_COMMAND=$(
    cat<<-'EOF'

    retval=$?

    RED=$(tput setaf 1)
    GREEN=$(tput setaf 2)
    STOP=$(tput sgr0)

    # arithmetic using bash parameter expansion on a array
    if (($retval + ${PIPESTATUS[@]/%/+} + 0)); then
        PS1="\[$RED\]\u@\h:\w$ \[$STOP\]"
    else
        PS1="\[$GREEN\]\u@\h:\w$ \[$STOP\]"
    fi
EOF
)

That will do the trick =)

Bash will run the code inside PROMPT_COMMAND for each commands.

If you have copy/paste problem, you can download the script

EXPLANATIONS

• (( )) is arithmetic in bash, see http://wiki.bash-hackers.org/syntax/arith_expr
• PROMPT_COMMAND : if set, the value is executed as a command prior to issuing each primary prompt. See man bash | less +/PROMPT_COMMAND
• tput is better than hard coding ANSI escape codes. See http://wiki.bash-hackers.org/scripting/terminalcodes
• PIPESTATUS : An array variable containing a list of exit status values from the processes in the most-recently-executed foreground pipeline (which may contain only a single command). See man bash | less +/PIPESTATUS
• cat<<-'EOF' is a special here doc : the - character means I can indent code, and the single quotes on 'EOF' means to not interpolate variables

Answer 2

I have a 2-line prompt, so the potentially long stuff won't affect the command line:

glennj@homebase ~/tmp
2219 $ set | grep PS1=
PS1='\n\u@\h \w\n\! \$ '

Answer 3

This is not a direct answer to the original question, it is just a usage example.

Based and thanks to @stArdustͲ's answer, I found a proper solution for a custom command prompt to show up the battery's status^*, on the top right corner of the terminal. The colors are defined in an independent file which is sourced from inside .bashrc.

PROMPT_COMMAND=$(
    cat<<-'EOF'
    function battery_percentage {
        PERCENTAGE=$(upower -i $(echo $(upower -e |grep 'battery')) |grep 'percentage' |sed -e 's/^[ \t]*//;s/[[:space:]]\+/ /g;s/[ \t]*$//' |cut -d' ' -f2 |cut -d"%" -f1)
        BColor='IGray'
        if [ "${PERCENTAGE}" -lt 15 ]
            then PColor='BlinkIRed'
                 PBackground='On_White'
            else PColor='Gray'
        fi
        echo "\001${!BColor}\002Battery\001${!PColor}\002 ${PERCENTAGE}% \001${Reset}\002"
    }

    function battery_time {
        TIME=$(upower -i $(echo $(upower -e |grep 'battery')) |grep 'time' |sed -e 's/^[ \t]*//;s/[[:space:]]\+/ /g;s/[ \t]*$//' |cut -d' ' -f4,5)
        echo "\001${IGray}\002${TIME}\001${Reset}\002"
    }

    export PS1="\[\e[s\]\[\e[1;\$((COLUMNS-26))f\]$(battery_percentage) $(battery_time)\[\e[u\]${PS1}"
EOF
)

Finally, the PS1 looks like:

\[\e[s\]\[\e[1;$((COLUMNS-26))f\]\001\e[0;38;5;8m\002Battery\001\e[0;38;5;7m\002 82% \001\e[0m\002 \001\e[0;38;5;8m\0023.6 hours\001\e[0m\002\[\e[u\]\[\e[0;38;5;232m\]\[\e[48;5;5m\] \u \[\e[0;38;5;5m\]\[\e[48;5;11m\] \[\e[0;38;5;232m\]\[\e[48;5;11m\]@\H \[\e[0;38;5;11m\]\[\e[48;5;0m\]\[\e[0m\] \[\e[0;38;5;6m\]\w\a \[\e[1;38;5;5m\]→\e[0m

Note, I do have some cursor positioning problems, though, when I scroll up and down through the command history.

---

_{* of a ThinkPad laptop}

Answer 4

Not \\[, just \[. You also have an extra \[ at the start.