Nicely formatting output to console, specifying number of tabs

Question

Provided you know the maximum length to be no more than 20 characters:

printf "%-20s %s\n", value_name, value

If you want to make it more dynamic, something like this should work nicely:

longest_key = data_hash.keys.max_by(&:length)
data_hash.each do |key, value|
  printf "%-#{longest_key.length}s %s\n", key, value
end

There is usually a %10s kind of printf scheme that formats nicely.
However, I have not used ruby at all, so you need to check that.

---

Yes, there is printf with formatting.
The above example should right align in a space of 10 chars.
You can format based on your widest field in the column.

printf ([port, ]format, arg...)

Prints arguments formatted according to the format like sprintf. If the first argument is the instance of the IO or its subclass, print redirected to that object. the default is the value of $stdout.

String has a built-in ljust for exactly this:

x = {"foo"=>37, "something long"=>42, "between"=>99}
x.each { |k, v| puts "#{k.ljust(20)} #{v}" }
# Outputs:
#  foo                  37
#  something long       42
#  between              99

Or, if you want tabs, you can do a little math (assuming tab display width of 8) and write a short display function:

def tab_pad(label, tab_stop = 4)
  label_tabs = label.length / 8
  label.ljust(label.length + tab_stop - label_tabs, "\t")
end

x.each { |k, v| puts "#{tab_pad(k)}#{v}" }
# Outputs: 
#  foo                  37
#  something long       42
#  between              99

There was few bugs in it before, but now you can use most of printf syntax with % operator:

1.9.3-p194 :025 > " %-20s %05d" % ['hello', 12]
 => " hello                00012" 

Of course you can use precalculated width too:

1.9.3-p194 :030 > "%-#{width}s %05x" % ['hello', 12]
  => "hello          0000c"