netCDF是一個非常通用的數(shù)據(jù)格式，大量的軟件都支持此格式的讀和寫，比如paraview, tecplot, surfer, gmt,matlab等等。所以如果自己寫的計算程序?qū)⑤敵鑫募袷娇蛇x 為netcdf那將是很方便使用的。

安裝netCDF

Mac系統(tǒng)下直接使用 brew install netcdf就可以安裝最新版的netcdf，默認(rèn)安裝目錄為 /usr/local/Cellar/netcdf/4.6.3_1，該目錄下有include, lib文件夾，會編程序的都知道這意味著什么！

代碼中使用netCDF

程序源碼

比如一個簡單的測試程序，來自netcdf源代碼中的例子,這段C++代碼是寫一個簡單的nc文件

#include <iostream>
#include <netcdf>
#include <vector>
using namespace std;
using namespace netCDF;
using namespace netCDF::exceptions;
// We are writing 2D data, a 6 x 12 grid. 
static const int NX = 6;
static const int NY = 12;
// Return this in event of a problem.
static const int NC_ERR = 2;

int main()
{
  int dataOut[NX][NY];
  for(int i = 0; i < NX; I++)
    for(int j = 0; j < NY; j++)
      dataOut[i][j] = i * NY + j;
  try
    {  
      NcFile dataFile("simple_xy.nc", NcFile::replace);
      NcDim xDim = dataFile.addDim("x", NX);
      NcDim yDim = dataFile.addDim("y", NY);
      vector<NcDim> dims;
      dims.push_back(xDim);
      dims.push_back(yDim);
      NcVar data = dataFile.addVar("data", ncInt, dims);
      data.putVar(dataOut);
      return 0; 
    }
  catch(NcException& e)
    {e.what();
      return NC_ERR;
    }
}

CMake文件

# CMake 最低版本號要求
cmake_minimum_required (VERSION 2.8)

# 項目信息
project (testnc)

# 添加頭文件目錄和鏈接庫目錄
include_directories(/usr/local/Cellar/netcdf/4.6.3_1/include )
link_directories(/usr/local/Cellar/netcdf/4.6.3_1/lib)

# 指定生成目標(biāo)
add_executable(testnc main.cpp)

# 添加鏈接庫
target_link_libraries(testnc netcdf-cxx4)

編譯生成

創(chuàng)建一個build目錄，然后進(jìn)入build目錄，使用命令 cmake ..生成makefile；最后用命令 make 就可以生成testnc可執(zhí)行文件，這個可執(zhí)行文件可以直接運行會生成一個simple_xy.nc的nc數(shù)據(jù)文件。

雷區(qū)

netcdf的lib文件夾下共有四個.a文件，我們在c++代碼中要使用的是libnetcdf-cxx4.a這個文件

netcdf的鏈接庫

如果設(shè)置為target_link_libraries(testnc netcdf)或target_link_libraries(testnc netcdf_c++)都會導(dǎo)致如下的編譯錯誤

[ 50%] Building CXX object CMakeFiles/testnc.dir/main.cpp.o
[100%] Linking CXX executable testnc
Undefined symbols for architecture x86_64:
  "netCDF::NcDim::NcDim(netCDF::NcDim const&)", referenced from:
      void std::__1::allocator<netCDF::NcDim>::construct<netCDF::NcDim>(netCDF::NcDim*, netCDF::NcDim const&) in main.cpp.o
  "netCDF::ncInt", referenced from:
      _main in main.cpp.o
  "netCDF::NcFile::NcFile(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, netCDF::Nc
File::FileMode)", referenced from:
      _main in main.cpp.o
  "netCDF::NcFile::~NcFile()", referenced from:
      _main in main.cpp.o
  "netCDF::NcVar::putVar(void const*) const", referenced from:
      _main in main.cpp.o
  "netCDF::NcGroup::addDim(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned 
long) const", referenced from:
      _main in main.cpp.o
  "netCDF::NcGroup::addVar(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, netCDF::NcType const&, std::__1::vector<netCDF::NcDim, std::__1::allocator<netCDF::NcDim> > const&) const", referenced from:
      _main in main.cpp.o
  "typeinfo for netCDF::exceptions::NcException", referenced from:
      GCC_except_table0 in main.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [testnc] Error 1
make[1]: *** [CMakeFiles/testnc.dir/all] Error 2
make: *** [all] Error 2