The -write_sec option writes the current grib message section (0-8)
to file. The only options that applies to the file are the -header,
-no_header, -append, and
The default -header option put a 4-byte unsigned integer header and trailer around the section data.
The header and trailer are the number of bytes of the section.
The -write_sec option is by codes that need low-level access to the grib data.
-write_sec N file N = 0..8
file = file to write
wgrib2 IN.grb -write_sec 0 sec0.dat -write_sec 1 sec1.dat -write_sec 2 sec2.dat -write_sec 3 sec3.dat \
-write_sec 4 sec4.dat -write_sec 5 sec5.dat -write_sec 6 sec6.dat -write_sec 7 sec7.dat