To compile:
   Need the following commands to be installed

     gcc         gnu C compiler
     gfortran    gnu Fortran compiler
     make        gnu make
     various sh utilies

   The includeemakefile/code is for the linux environment.  
To compile type

   $ tar -xzf gfsnemsio2grb.tgz
   $ cd gfsnesmsio2grb
   $ make
   makefile:43: *** ERROR, get wgrib2 source by "wget https://www.ftp.cpc.ncep.noaa.gov/wd51we/wgrib2/wgrib2.tgz".  Stop.

The gfsnemsio2grb distribution does not include a copy of wgrib2.  You 
can download the wgrib2 code as suggested by the error message.

   $ wget https://www.ftp.cpc.ncep.noaa.gov/wd51we/wgrib2/wgrib2.tgz

This will retrieve a copy of wgrib2.tgz.  Now to continue the make by

   $ make

If all goes well, you will find the executable in bin/gfsnemsio2grb

   $ cp bin/gfsnesmio2grb (directory on your path)

You will find the documentation for the code at 

     https://www.cpc.ncep.noaa.gov/products/wesley/gfsnemsio2grb.html