wgrib2           revised 7.2016, 2.2021

wgrib2 is a program to read/write grib2 files.


For documentation, see

    http://www.cpc.ncep.noaa.gov/products/wesley/wgrib2/index.html


For documentation of commonly used program options, type

    wgrib2


For documentation of all program options, type

   wgrib2 -help all

For documenation of any program option that is poorly described on-line
or by the "wgrib2 -help all", check the source code by searching
for "f_{option}" where the option does not include the minus sign.


Default makefile options

	USE_NETCDF3=1
	USE_NETCDF4=0
	USE_REGEX=1
	USE_TIGGE=1
	USE_MYSQL=0
	USE_IPOLATES=3
        USE_SPECTRAL=1
	USE_UDF=0
	USE_OPENMP=1
	USE_PROJ4=0
	USE_WMO_VALIDATION=0
	DISABLE_TIMEZONE=0
	MAKE_FTN_API=0
        MAKE_SHARED_LIB=0

	USE_G2CLIB=0
	USE_PNG=1
	USE_JASPER=1
	USE_OPENJPEG=1
	USE_AEC=1

To compile without netcdf,    set USE_NETCDF3=0 and USE_NETCDF4=0
To compile with netcdf v3, set USE_NETCDF3=1 and USE_NETCDF4=0
To compile with netcdf v4, set USE_NETCDF3=0 and USE_NETCDF4=1

For netcdf4, the netcdf4 and hdf5 libraries are usually not included 
  in the wgrib2.tgz file to save space.  The makefile suggests
  how to download the netcdf4 and hdf5 libraries.

If you have non-POSIX C compiler system that doesn't include <regex.h>, then
you have to set USE_REGEX=0.  This disables the use of regular expressions. 

No harm to keep TIGGE support on.  USE_TIGGE=1

Support for Mysql is an option.  You have to modify the makefile to indicate 
the locations of the mysql includes and libraries and set USE_MYSQL=1

The option -new_grid uses the ipolates library to do the interpolation.
The default is to USE_IPOLATES=3, and USE_SPECTRAL=1.  The interpolation
libraries are written in fortran and work with the supported compilers.
For other compilers, you are on your own.  The source code and makefile 
will have to be modified to use the ipolates option.  Consult a local 
expert if you want to install this optional package.  No help is available 
from NCEP for installing the package.

User Defined Functions (UDF) allow you to run shell commands from
within wgrib2. UDF are not available on windows machines unless
<unistd.h> is implimented by the compiler (cygwin, MinGW).  For
the security paranoid, turn off UDF by USE_UDF=0.  

OpenMP allows wgrib2 to run on many cores for a faster run time.  See 
README.openmp.  The USE_OPENMP option will compile wgrib2 with openmp 
for several compilers.

Proj4 is a open-source geolocation library.  Usually the faster gctpc library
is used for geolocation.  At the current time, Proj4 does not add any
capabilty over gctpc.

Wgrib2 has been used to test proposals to the WMO grib standard.  Developers
might want to have conditional compilation of the tests using 

        #ifdef WMO_VALIDATION
            ... test code ...
        #endif

and compile using

	USE_WMO_VALIDATION=1


If you have a non-POSIX C compiler system that doesn't support time zones
or supports time zones in a non-POSIX manner, then you have to set
DISABLE_TIMEZONE to 1.

Wgrib2 is both a stand alone utility and a library that is callable
from both C, Fortran and python.  To enable the making the wgrib2 library, 
you have to set

	MAKE_FTN_API=1

For use with python, you have to make a shared library using

        MAKE_SHARED_LIB=1

To make a library, you have tocompile by

        $ make lib

In older versions of wgrib2, the g2clib was the default decoder of grib files.
In the current version, you can use g2clib as an optional decoder.  The main 
use of compiling wgrib2 with g2clib is for testing g2clib.

	USE_G2CLIB=1

Support for the png, jpeg2000 and CDCSD(AEC) compression can be turned off through 
the following options.

	USE_PNG=0
	USE_JASPER=0
        USE_OPENJPEG=0
        USE_AEC=0

Some of the optional libraries require CMake.  Some of the optional libraries will
run a configure script.  Both features can make cross compiling difficult.