Compiling and Linking Fortran Code with external modules and libraries

Dear all,

I am trying to create a fortran program. I have already done this in Windows and using Visual Studio.

In linux I am using ifort (ifort (IFORT) 14.0.2 20140120).

I am very new to this. I appreciate your help. I will explain the procedure I am taking below.

I have my source code ( File1.f90, File2.f90, File3.f90 and main.f90) and then I have a folder full of external libraries (*.a and *.mod )

I have not written these libraries nor I have any idea which compiler was used to compile and create those libraries.

I try to first compile my files using the following:

File1.90  and File2.f90 are not using these external libraries while File3.90 is using these external libraries. At last main.f90 is using File3.90. In order to compile I have used the following commands:

ifort -c File1.f90

ifort -c File2.f90

ifort -c File3.f90 -I  mylib&modulesDirectoryAddress     

ifort -c main.f90  -I  mylib&modulesDirectoryAddress

All files are compiled successfully but when I try to link them using the following command I ran in to error :

ifort  File1.o File2.o File3.o main.o -I  mylib&modulesDirectoryAddress

The error is this:

File3.f90 undefined reference to `m_get_mp_myFunction_'

myFunction is a function that I call inside File3.f90 from one of the external modules/libraries.

 subroutine File3_internalFunction
    use externalModule, only : myFunction
      implicit none

      !external
      character(len=*), intent(in) :: fname
      integer,          intent(in) :: timeStep
      character(len=32), intent(in)::  vname
      real, pointer   :: varValue(:)
      logical:: stopIfNotPresent
      character(len=256) ::  firstPartOfString
      character(len=80) ::  outpStr

      varValue => myFunction(fname, vname, timeStep)
   
    end subroutine

Could you please let me know what is the possible reason that I am getting the above error?  Also do I need to have additional compile or link options that I am missing right now ? I am coming from Visual Studio and I am  quite confused how to get the same exectuable here?

Also are there any system-dependent options that I will need to define?I am trying to get an executable for 64-bit Linux systems.

I would really appreciate your help.

Thank you very much in Advance for your help.

Kind Regards,

Heli