#!/bin/bash
function comment_line() {
    local regex="${1:?}"
    local file="${2:?}"
    local comment_mark="${3:-#}"
    sed -ri "s:^([ ]*)($regex):\\1$comment_mark\\2:" "$file"
}

function uncomment_line() {
    local regex="${1:?}"
    local file="${2:?}"
    local comment_mark="${3:-#}"
    sed -ri "s:^([ ]*)[$comment_mark]+[ ]?([ ]*$regex):\\1\\2:" "$file"
}