Practical Fortran

File I/O

Scratch Unit

A scratch file is a unit with no name that is opened and discarded automatically. Useful for short-lived buffers.

Program

Play the program to write a number to a scratch unit, rewind, read it back, and double it.

file_io.f90 
program file_io_demo
    implicit none
    integer :: unit_, value_in, value_out
    value_in = 42
    open(newunit=unit_, status='scratch', action='readwrite')
    write(unit_, '(I0)') value_in
    rewind(unit_)
    read(unit_, *) value_out
    close(unit_)
    print '(I0)', value_out * 2
end program file_io_demo
scratch `status='scratch'` opens a temporary unit deleted on close.
newunit `newunit=unit_` picks an unused unit number.
rewind `rewind` returns the file position to the start before reading.