cheat sheets.

$ command line ruby cheat sheets
%b    => Binary integer
%c    => Single character
%d    => Decimal integer
%e    => Decimal integer displayed in exponential form (3e+07)
%E    => Decimal integer displayed in exponential form (3E+07)
%f    => Floating point number
%g    => Same as %e if exponent is less than -4, %f otherwise
%G    => Same as %E if exponent is less than -4, %f otherwise
%o    => Octal integer
%s    => String
%u    => Unsigned decimal integer
%x    => Hexadecimal integer (2a)
%X    => Hexadecimal integer uppercase (2A)
%02d  => 0 padded two digits
%.02f => round to the hundredths
%+    => +/- sign

width & alignment
"%10s" % "hello" => "     hello"    
"%-10s" % "hello" => "hello     "