在C ++中为非现有函数抛出错误

Question

我正在编写C ++程序并在执行时遇到以下错误：

系统未在此范围内声明

#include <iostream>
#include "commands.h"

using namespace std;


void retrieveDataset(const char* input) 
{
const char* command = "wget ";
std::string buf(command);
buf.append(input);
const char * c = buf.c_str();
system(c);
}

void generateInputLayer(const char* input)
{
const char * start = "generateNetCDF -d gl_input -i ";
std::string buf(start);
buf.append(input);
const char * end = " -o gl_input.nc -f features_input -s samples_input -c";
buf.append(end);
const char * c = buf.c_str();
system(c);
}

void generateOutputLayer(const char * input)
{
const char * start = "generateNetCDF -d gl_output -i ";
std::string buf(start);
buf.append(input);
const char * end = " -o gl_output.nc -f features_output -s samples_input -c";
buf.append(end);
const char * c = buf.c_str();
system(c);
}

void train(int batchSize, int num_epochs)
{
const char * start = "train -c config.json -i gl_input.nc -o gl_output.nc -n gl.nc -b ";
std::string buf(start);
std::string batchString = std::to_string(batchSize);
std::string epochString = std::to_string(num_epochs);
char const *b = batchString.c_str();
char const *e = epochString.c_str();
buf.append(b);
const char * middle =  " -e ";
buf.append(middle);
buf.append(e);
const char * c = buf.c_str();
std::cout << c;
system(c);
}

void predict(int num_recommendations, const char * input) 
{
const char * start = "predict -b 1024 -d gl -i features_input -o features_output -k ";
std::string buf(start);
std::string recString = std::to_string(num_recommendations);
char const *r = recString.c_str();
buf.append(r);
const char * next = " -n gl.nc -f ";
buf.append(next);
buf.append(input);
const char * last = " -s recs -r ";
buf.append(last);
buf.append(input);
const char * c = buf.c_str();
system(c);
}

系统正在向我提出错误：错误：在此范围系统中未声明'system'（c）; 系统（c）在代码中的位置。

Commands.h文件如下：

#include <stdio.h>
#include <iostream>

void retrieveDataset(const char* input);
void generateInputLayer(const char* input);
void generateOutputLayer(const char * input);
void train(int batchSize, int num_epochs);
void predict(int num_recommendations, const char * input);

请帮助。 C ++新手