diff --git a/.github/workflows/Linux_options.yml b/.github/workflows/Linux_options.yml
index 9611cc2f..7a80c83b 100644
--- a/.github/workflows/Linux_options.yml
+++ b/.github/workflows/Linux_options.yml
@@ -30,6 +30,9 @@ jobs:
         - {
             options: "-DUSE_IPOLATES=1"
           }
+        - {
+            options: "-DUSE_NETCDF4=ON"
+          }
           
     steps:
 
@@ -40,7 +43,7 @@ jobs:
         sudo apt-get install libpng-dev autotools-dev autoconf
 
     - name: checkout-jasper
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with:
         repository: jasper-software/jasper
         path: jasper
@@ -55,7 +58,7 @@ jobs:
         make install
 
     - name: checkout-sp
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with:
         repository: NOAA-EMC/NCEPLIBS-sp
         path: sp
@@ -96,7 +99,7 @@ jobs:
         make install
           
     - name: checkout-ip2
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with:
         repository: NOAA-EMC/NCEPLIBS-ip2
         path: ip2
@@ -112,7 +115,7 @@ jobs:
         make install        
 
     - name: checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with: 
         path: wgrib2
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8417db41..b3f74c11 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -34,14 +34,12 @@ option(USE_AEC "Use AEC?" off)
 option(MAKE_FTN_API "add ftn api?" off)
 option(DISABLE_STAT "disable posix feature" off)
 set(BUILD_COMMENTS "stock build")
-
 option(BUILD_LIB "Build wgrib2 library?" on)
 option(BUILD_SHARED_LIB "Build shared library?" off)
 
-
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
-#set default install path if not provided
+# Set default install path if not provided.
 if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
   set(CMAKE_INSTALL_PREFIX
     "${CMAKE_BINARY_DIR}/install"
@@ -50,6 +48,7 @@ endif()
 
 include(GNUInstallDirs)
 
+# Set compiler flags.
 message(STATUS "Setting compiler flags...")
 if(CMAKE_C_COMPILER_ID MATCHES "^(Intel)$")
   set(CMAKE_C_FLAGS "-g -traceback ${CMAKE_C_FLAGS} -DIFORT")
@@ -67,7 +66,6 @@ elseif(CMAKE_Fortran_COMPILER_ID MATCHES "^(GNU)$")
   set(CMAKE_Fortran_FLAGS_DEBUG "-ggdb -O0")
 endif()
 
-
 message(STATUS "Checking if user wants to use NCEPLIBS-g2c...")
 if(USE_G2CLIB) 
   if(USE_PNG) 
@@ -129,12 +127,13 @@ if(USE_PNG)
   find_package(PNG REQUIRED)
 endif()
 
-# write config.h
+# Start to write config.h.
 message(STATUS "Writing config.h...")
 FILE(WRITE "wgrib2/config.h" "/* config.h generated by cmake */\n")
 FILE(APPEND "wgrib2/config.h" "#ifndef _CONFIG_H\n")
 FILE(APPEND "wgrib2/config.h" "#define _CONFIG_H\n")
 
+# Add lines to config.h for each of the user options.
 FOREACH(var IN ITEMS USE_NETCDF3 USE_NETCDF4 USE_HDF5 USE_REGEX USE_TIGGE USE_MYSQL
    USE_IPOLATES USE_UDF USE_OPENMP USE_PROJ4 USE_WMO_VALIDATION DISABLE_TIMEZONE
    DISABLE_ALARM USE_NAMES USE_G2CLIB USE_PNG USE_JASPER USE_OPENJPEG MAKE_FTN_API USE_AEC BUILD_COMMENTS)
@@ -151,16 +150,19 @@ FOREACH(var IN ITEMS USE_NETCDF3 USE_NETCDF4 USE_HDF5 USE_REGEX USE_TIGGE USE_MY
    endif()
 ENDFOREACH()
 
+# Add some compiler information to config.h.
 FILE(APPEND "wgrib2/config.h" "#define CC \"${CMAKE_C_COMPILER} ${CMAKE_C_COMPILER_ID}\"\n")
 FILE(APPEND "wgrib2/config.h" "#define FORTRAN \"${CMAKE_Fortran_COMPILER} ${CMAKE_Fortran_COMPILER_ID}\"\n")
 FILE(APPEND "wgrib2/config.h" "#define CPPFLAGS \"${CMAKE_C_FLAGS}\"\n")
 FILE(APPEND "wgrib2/config.h" "#define FFLAGS \"${CMAKE_Fortran_FLAGS}\"\n")
 FILE(APPEND "wgrib2/config.h" "#endif\n")
 
+# Compile the wgrib2 code.
 message(STATUS "Adding wgrib2, aux_probs subdirectories...")
 add_subdirectory(wgrib2)
 add_subdirectory(aux_progs)
 
+# Build wgrib2 library if desired.
 if(BUILD_LIB)
   message(STATUS "Adding wgrib2 library build...")
   ### Package config