Lua: string of specific length

Question

local data = "here is a string"
local no = 12
foo = string.format("%50s %05d",data,no)
print(foo:len(),string.format("%q",foo))

defines foo as a string of specific length

"                                  here is a string 00012"

However, is there an easy way to get

"here is a string                                   00012"

I know, that I can fill up the string data with spaces

while data:len() < 50 do data = data.." " end

Answer 1

Add a minus to format string %-50s to align text to the left:

foo = string.format("%-50s %05d","here is a string", 12)
print(foo:len(), foo)

Output:

56  here is a string                                   00012

Allowed flags:

- : left align result inside field
+ : always prefix with a sign, using + if field positive
0 : left-fill with zeroes rather than spaces
(space) : If positive, put a space where the + would have been
# : Changes the behaviour of various formats, as follows:
  For octal conversion (o), prefixes the number with 0 - if necessary.
  For hex conversion (x), prefixes the number with 0x
  For hex conversion (X), prefixes the number with 0X
  For e, E and f formats, always show the decimal point.
  For g and G format, always show the decimal point, and do not truncate trailing zeroes.
  The option to 'always show the decimal point' would only apply if you had the precision set to 0.