Get a free file unit number

[jaeger0]

I have maybe a trivial question, but however I can not fount the function in the manual.

I'm using a lot of files, so I want to use an unique file unit-number, not used somewhere else at the same time. Is there a method to proof if a file-unit is arlready used ?

[GVautier]

[cpp]
integer*4 function get_free_file_unit_number

integer*4, parameter :: first_unit=  10
integer*4, parameter :: last_unit =9999
logical*4 test

do get_free_file_unit_number=first_unit,last_unit
    inquire(get_free_file_unit_number,opened=test)
    if (.not.test) return
enddo
get_free_file_unit_number=-1
end function[/cpp]