ljust(*args)
If integer is greater than the length of str, returns a new String of length integer with str left justified and padded with padstr; otherwise, returns str.
"hello".ljust(4) #=> "hello" "hello".ljust(20) #=> "hello " "hello".ljust(20, '1234') #=> "hello123412341234123"
static VALUE rb_str_ljust(int argc, VALUE *argv, VALUE str) { return rb_str_justify(argc, argv, str, 'l'); }