# PRINT input file section

This is a very simple section that allows linear combinations of calculated properties to be written to standard output. The syntax of this section is:

    PRINT {what} [id op id op...] END

The first mandatory argument is `what`, the quantity to manipulate or print. This variable is a string that can assume the following values:

`elecEnergy`
  Print electrostatic energies as calculated with an earlier ELEC input file section calcenergy command.
`elecForce`
  Print electrostatic forces as calculated with an earlier ELEC input file section calcforce command.
`apolEnergy`
  Print apolar energies as calculated with an earlier APOLAR input file section calcenergy command.
`apolForce`
  Print electrostatic forces as calculated with an earlier APOLAR input file section calcforce command.

The next arguments are a series of `id op id op id op ... id` commands where every `id` is immediately followed by an `op` and another `id`.

`id`
  This is a variable string or integer denoting the ID of a particular ELEC input file section or APOLAR input file section calculations. String values of `id` correspond to the optional “names” that can be assigned to ELEC input file section or APOLAR input file section calculations. Integer values of id are assumed to corresponding to the sequentially-assigned integer IDs for ELEC input file section or APOLAR input file section calculations. These IDs start at 1 and are incremented (independently) for each new ELEC input file section or APOLAR input file section calculation.
`op`
  Specify the arithmetic operation (`+` for addition and `-` for subtraction) to be performed on the calculated quantities

For example:

    # Energy change due to binding
    print energy complex - ligand - protein end
    # Energy change due to solvation
    print energy solvated - reference end
    # Solvation energy change due to binding
    print energy complex_solv - complex_ref - ligand_solv + ligand_ref - protein_solv + protein_ref end