Underline a string until the end of the line

Question

I have the following code which displays a message based on whether or not the last command was executed successfully (which is prepended to PS1):

function previous_command() {
    exit_code=$?
    if [ $exit_code -eq 0 ]; then
        echo -e "\033[1;4;32mCommand successful\033[00m"
    else
        echo -e "\033[1;4;31mCommand failed with exit code $exit_code\033[00m"
    fi
}

What I want to do is have the underline extend all the way to the edge of the current terminal window, like this:

Assuming the exit code is one character long, I can hard-code it to 80 characters by just adding spaces, but this fails if I resize the window or get an exit code of 10 or greater.

How can I make this function dynamically continue the line to the edge of the terminal window?

Answer 1

You can left align a string with spaces to 42 characters with printf "%-42s". You can get the window width with $COLUMNS. Putting them together, we get:

printf "\033[1;4;31m%-${COLUMNS}s\033[00m" "Command failed with $RANDOM"

No matter how many digits the (here random) number is, the line always extends all the way to the edge.