C++读写文件

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
	fstream myFile;
	myFile.open("saldina.txt", ios::out);  // write,清空再写入
	if (myFile.is_open())
	{
		myFile << "Hello\n";
		myFile << "This is second line\n";
		myFile.close();
	}
	myFile.open("saldina.txt", ios::app);  // append,追加
	if (myFile.is_open())
	{
		myFile << "Hello2\n";
		myFile << "This is third line\n";
		myFile.close();
	}
	myFile.open("saldina.txt", ios::in);  // read,读
	if (myFile.is_open())
	{
		string line;
		while (getline(myFile, line))
		{
			cout << line << endl;
		}
		myFile.close();
	}
}

#include <string>
#include <fstream>
#include <vector>

void write_csv(std::string filename, std::string colname, std::vector<int> vals){
    // Make a CSV file with one column of integer values
    // filename - the name of the file
    // colname - the name of the one and only column
    // vals - an integer vector of values
    
    // Create an output filestream object
    std::ofstream myFile(filename);
    
    // Send the column name to the stream
    myFile << colname << "\n";
    
    // Send data to the stream
    for(int i = 0; i < vals.size(); ++i)
    {
        myFile << vals.at(i) << "\n";
    }
    
    // Close the file
    myFile.close();
}

int main() {
    // Make a vector of length 100 filled with 1s
    std::vector<int> vec(100, 1);
    
    // Write the vector to CSV
    write_csv("ones.csv", "Col1", vec);
    
    return 0;
}

#include <string>
#include <fstream>
#include <vector>
#include <utility> // std::pair

void write_csv(std::string filename, std::vector<std::pair<std::string, std::vector<int>>> dataset){
    // Make a CSV file with one or more columns of integer values
    // Each column of data is represented by the pair <column name, column data>
    //   as std::pair<std::string, std::vector<int>>
    // The dataset is represented as a vector of these columns
    // Note that all columns should be the same size
    
    // Create an output filestream object
    std::ofstream myFile(filename);
    
    // Send column names to the stream
    for(int j = 0; j < dataset.size(); ++j)
    {
        myFile << dataset.at(j).first;
        if(j != dataset.size() - 1) myFile << ","; // No comma at end of line
    }
    myFile << "\n";
    
    // Send data to the stream
    for(int i = 0; i < dataset.at(0).second.size(); ++i)
    {
        for(int j = 0; j < dataset.size(); ++j)
        {
            myFile << dataset.at(j).second.at(i);
            if(j != dataset.size() - 1) myFile << ","; // No comma at end of line
        }
        myFile << "\n";
    }
    
    // Close the file
    myFile.close();
}

int main() {
    // Make three vectors, each of length 100 filled with 1s, 2s, and 3s
    std::vector<int> vec1(100, 1);
    std::vector<int> vec2(100, 2);
    std::vector<int> vec3(100, 3);
    
    // Wrap into a vector
    std::vector<std::pair<std::string, std::vector<int>>> vals = {{"One", vec1}, {"Two", vec2}, {"Three", vec3}};
    
    // Write the vector to CSV
    write_csv("three_cols.csv", vals);
    
    return 0;
}

#include <string>
#include <fstream>
#include <vector>
#include <utility> // std::pair
#include <stdexcept> // std::runtime_error
#include <sstream> // std::stringstream

std::vector<std::pair<std::string, std::vector<int>>> read_csv(std::string filename){
    // Reads a CSV file into a vector of <string, vector<int>> pairs where
    // each pair represents <column name, column values>

    // Create a vector of <string, int vector> pairs to store the result
    std::vector<std::pair<std::string, std::vector<int>>> result;

    // Create an input filestream
    std::ifstream myFile(filename);

    // Make sure the file is open
    if(!myFile.is_open()) throw std::runtime_error("Could not open file");

    // Helper vars
    std::string line, colname;
    int val;

    // Read the column names
    if(myFile.good())
    {
        // Extract the first line in the file
        std::getline(myFile, line);

        // Create a stringstream from line
        std::stringstream ss(line);

        // Extract each column name
        while(std::getline(ss, colname, ',')){
            
            // Initialize and add <colname, int vector> pairs to result
            result.push_back({colname, std::vector<int> {}});
        }
    }

    // Read data, line by line
    while(std::getline(myFile, line))
    {
        // Create a stringstream of the current line
        std::stringstream ss(line);
        
        // Keep track of the current column index
        int colIdx = 0;
        
        // Extract each integer
        while(ss >> val){
            
            // Add the current integer to the 'colIdx' column's values vector
            result.at(colIdx).second.push_back(val);
            
            // If the next token is a comma, ignore it and move on
            if(ss.peek() == ',') ss.ignore();
            
            // Increment the column index
            colIdx++;
        }
    }

    // Close file
    myFile.close();

    return result;
}

int main() {
    // Read three_cols.csv and ones.csv
    std::vector<std::pair<std::string, std::vector<int>>> three_cols = read_csv("three_cols.csv");
    std::vector<std::pair<std::string, std::vector<int>>> ones = read_csv("ones.csv");

    // Write to another file to check that this was successful
    write_csv("three_cols_copy.csv", three_cols);
    write_csv("ones_copy.csv", ones);
    
    return 0;
}

#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <sstream>
 
using namespace std;
 
int main()
{
	string fname;
	cout<<"Enter the file name: ";
	cin>>fname;
 
	vector<vector<string>> content;
	vector<string> row;
	string line, word;
 
	fstream file (fname, ios::in);
	if(file.is_open())
	{
		while(getline(file, line))
		{
			row.clear();
 
			stringstream str(line);
 
			while(getline(str, word, ','))
				row.push_back(word);
			content.push_back(row);
		}
	}
	else
		cout<<"Could not open the file\n";
 
	for(int i=0;i<content.size();i++)
	{
		for(int j=0;j<content[i].size();j++)
		{
			cout<<content[i][j]<<" ";
		}
		cout<<"\n";
	}
 
	return 0;
}

/**
 * @description - Read any ASCII,BINARY or HEX file.
 * @param - Source file name and file type.
 * @return - Returns data in tuple format,use std::get<TUPLE_ID>(TUPLE_OBJ) to get data.
 */
/*Including STD-C++ libraries*/
#include <iostream> /*For basic I/O.*/
#include <fstream> /*For basic I/O.*/
#include <sstream> /*For basic I/O.*/
#include <vector> /*For STL vector.*/
#include <tuple>  /*For packing multi data.*/

using std::string;

#define BINARY_FILE 0
#define ASCII_FILE 1
#define HEX_FILE 2
std::tuple<std::vector<uint8_t>, string, string> ReadFile(string, int);
bool WriteFile(string file_name, string, int);

/*
Example of binary file:
	auto file_type = ReadFile("user_data.dat", BINARY_FILE);
	auto file_data = std::get<BINARY_FILE>(file_type);

Example of ASCII file:
	auto file_type = ReadFile("my_file.txt", ASCII_FILE);
	auto file_data = std::get<ASCII_FILE>(file_type);
*/

std::tuple<std::vector<uint8_t>, string, string> ReadFile(string file_name, int file_type)
{
	/*Buffers to store output data from file.*/
	string str_buf, hex_buf;
	std::vector<uint8_t> vec_buf;

	try {
		if (file_type == BINARY_FILE) {

			/*Open the stream in binary mode.*/
			std::ifstream bin_file(file_name, std::ios::binary);

			if (bin_file.good()) {
				/*Read Binary data using streambuffer iterators.*/
				std::vector<uint8_t> v_buf((std::istreambuf_iterator<char>(bin_file)), (std::istreambuf_iterator<char>()));
				vec_buf = v_buf;
				bin_file.close();
			}

			else {
				throw std::exception();
			}

		}

		else if (file_type == ASCII_FILE) {

			/*Open the stream in default mode.*/
			std::ifstream ascii_file(file_name);
			string ascii_data;

			if (ascii_file.good()) {
				/*Read ASCII data using getline*/
				while (getline(ascii_file, ascii_data))
					str_buf += ascii_data + "\n";

				ascii_file.close();
			}
			else {
				throw std::exception();
			}
		}

		else if (file_type == HEX_FILE) {

			/*Open the stream in default mode.*/
			std::ifstream hex_file(file_name);

			if (hex_file.good()) {
				/*Read Hex data using streambuffer iterators.*/
				std::vector<char> h_buf((std::istreambuf_iterator<char>(hex_file)), (std::istreambuf_iterator<char>()));
				string hex_str_buf(h_buf.begin(), h_buf.end());
				hex_buf = hex_str_buf;

				hex_file.close();
			}
			else {
				throw std::exception();
			}
		}

	}

	catch (std::exception const& ex) {
		string ex_str = "Error: " + file_name + ": No such file or directory";
		throw std::exception(ex_str.c_str());
	}

	auto tuple_data = make_tuple(vec_buf, str_buf, hex_buf);
	return tuple_data;
}

/**
 * @description - Write data to any ASCII,BINARY or HEX file.
 * @param - Source file name, file data and file type.
 * @return - Returns true on successfully written data otherwise returns false.
 */

bool WriteFile(string file_name, string file_data, int file_type)
{
	bool write_status = false;
	std::ofstream out_stream(file_name, (file_type == ASCII_FILE) ? std::ios::out : (file_type == BINARY_FILE || file_type == HEX_FILE) ? std::ios::binary : std::ios::out);

	if (out_stream.is_open()) {
		if (file_type == ASCII_FILE) {
			out_stream << file_data;
			write_status = true;
		}

		else if (file_type == BINARY_FILE) {
			out_stream << file_data;
			write_status = true;
		}

		else if (file_type == HEX_FILE) {
			int bin_data;
			std::stringstream ss;
			ss << std::hex << file_data;

			while (ss >> bin_data)
				out_stream.write(reinterpret_cast<const char*>(&bin_data), sizeof(char));

			write_status = true;
		}
		out_stream.close();
	}
	else {
		string ex_str = "Error: couldn't open " + file_name + " for output";
		throw std::exception(ex_str.c_str());
	}
	return write_status;
}

Begin
   Create a structure Student to declare variables.
   Open binary file to write.
   Check if any error occurs in file opening.
   Initialize the variables with data.
   If file open successfully, write the binary data using write method.
      Close the file for writing.
   Open the binary file to read.
   Check if any error occurs in file opening.
   If file open successfully, read the binary data file using read method.
      Close the file for reading.
   Check if any error occurs.
   Print the data.
End.

#include<iostream>
#include<fstream>
using namespace std;
struct Student {
   int roll_no;
   string name;
};
int main() {
   ofstream wf("student.dat", ios::out | ios::binary);
   if(!wf) {
      cout << "Cannot open file!" << endl;
      return 1;
   }
   Student wstu[3];
   wstu[0].roll_no = 1;
   wstu[0].name = "Ram";
   wstu[1].roll_no = 2;
   wstu[1].name = "Shyam";
   wstu[2].roll_no = 3;
   wstu[2].name = "Madhu";
   for(int i = 0; i < 3; i++)
      wf.write((char *) &wstu[i], sizeof(Student));
   wf.close();
   if(!wf.good()) {
      cout << "Error occurred at writing time!" << endl;
      return 1;
   }
   ifstream rf("student.dat", ios::out | ios::binary);
   if(!rf) {
      cout << "Cannot open file!" << endl;
      return 1;
   }
   Student rstu[3];
   for(int i = 0; i < 3; i++)
      rf.read((char *) &rstu[i], sizeof(Student));
   rf.close();
   if(!rf.good()) {
      cout << "Error occurred at reading time!" << endl;
      return 1;
   }
   cout<<"Student's Details:"<<endl;
   for(int i=0; i < 3; i++) {
      cout << "Roll No: " << wstu[i].roll_no << endl;
      cout << "Name: " << wstu[i].name << endl;
      cout << endl;
   }
   return 0;
}

ofstream outfile("binary.txt", ofstream::binary);
string text = "Hello cplusplus forum!";
outfile.write((char*)&text, text.size());
outfile.close();

char* buffer = (char*)malloc(sizeof(string));
ifstream infile("binary.txt", ifstream::binary);
infile.read(buffer, sizeof(string));
string* elem = (string*)buffer;
cout << *elem << '\n';
infile.close();

ofstream outfile("binary.txt", ofstream::binary);
string text = "Hello cplusplus forum!";
outfile.write((char*)&text, text.size());
outfile.close();

unsigned int size = text.size();
outfile.write(reinterpret_cast<char *>(&size), sizeof(size)  );

#include <iostream>
#include <fstream>
#include <string>

using namespace std;
    
int main()
{   

    string text = "Hello cplusplus forum!";

    ofstream outfile("binary.txt", ofstream::binary);
    unsigned int size = text.size();                                 // get the size
    outfile.write(reinterpret_cast<char *>(&size), sizeof(size)  );  // write it to the file
    outfile.write( text.c_str(), text.size() );                      // write the actual text
    outfile.close();


    //----------------------------------------

    ifstream infile("binary.txt", ifstream::binary);
    
    // read the size
    size = 0;        
    infile.read(reinterpret_cast<char *>(&size), sizeof(size)  );
    
    // Allocate a string, make it large enough to hold the input
    string buffer;
    buffer.resize(size);
    
    // read the text into the string
    infile.read(&buffer[0],  buffer.size() );
    infile.close();    
    
    cout << "buffer = \n" << buffer << '\n';
    
}

mkdir build
cd build
cmake ..

custom_db:
    db_domain: 10.0.0.8
    db_username: root
    db_passwd: my_passwd
    db_schema: test

redis:
    redis_domain: 10.0.0.10
    redis_passwd: 123456

hello:
    num_config: [1141studio]
    name_config: [powered, by, 1141studio]

#include <iostream>
#include <string>
#include <stdio.h>
#include <unistd.h>
#include "yaml-cpp/yaml.h"
#include <vector>
const std::string DB_CONF = "config.yaml";
int main(int argc, char * argv[]) {
    /*----------------------------------- test yaml ----------------------------------------*/
    printf("hello world\n");
    std::cout << "this code is only for test yaml" << std::endl;

    /* Node conf. */
    YAML::Node conf = YAML::LoadFile(DB_CONF);
    
    /*----------------------------------- display db_config ----------------------------------------*/
    std::cout << "Database:"<< std::endl;
    std::cout << "domain:  " << conf["custom_db"]["db_domain"].as<std::string>() << std::endl;
    std::cout << "username:" << conf["custom_db"]["db_username"].as<std::string>() << std::endl;
    std::cout << "passwd:  " << conf["custom_db"]["db_passwd"].as<std::string>() << std::endl;
    std::cout << "schema:  " << conf["custom_db"]["db_schema"].as<std::string>() << std::endl;

    /*----------------------------------- display redis ----------------------------------------*/
    std::cout << "Redis" << std::endl;
    std::cout << "redis_domain: " << conf["redis"]["redis_domain"].as<std::string>() << std::endl;
    std::cout << "redis_passwd: " << conf["redis"]["redis_passwd"].as<std::string>() << std::endl;
    
    /*----------------------------------- display hello ----------------------------------------*/
    std::cout << "HelloServer" << std::endl;
    
    /* vector of name string. */
    std::vector<std::string> name_vec = conf["hello"]["num_config"].as<std::vector<std::string> >();
    if(!name_vec.empty())
      std::cout << name_vec[0] << std::endl;
    return 0;
}

cmake_minimum_required(VERSION 3.5.1)
project(nanodet-mnn)
SET(CMAKE_BUILD_TYPE "Release")

SET(CMAKE_CXX_FLAGS_RELEASE "$ENV{CXXFLAGS} -O3 -Wall")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall")
set(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/)

# yaml-cpp的包含目录
include_directories("/gzy_mnt/YAML_X86/include")
file(GLOB SOURCE_FILES *.cpp)
add_executable(${CMAKE_PROJECT_NAME} ${SOURCE_FILES})

target_link_libraries (
        ${CMAKE_PROJECT_NAME}   
        pthread
        /gzy_mnt/YAML_X86/lib/libyaml-cpp.so
)

name: frank
sex: male
age: 18
 
skills: 
    c++: 1
    java: 1
    android: 1
    python: 1

#include <iostream>
#include "yaml-cpp/yaml.h"
#include <fstream>
 
using namespace std;
 
int main(int argc,char** argv)
{
    YAML::Node config;
    try{
         config = YAML::LoadFile("../config.yaml");
    }catch(YAML::BadFile &e){
        std::cout<<"read error!"<<std::endl;
        return -1;
    }
    
    cout << "Node type " << config.Type() << endl;
    cout << "skills type " << config["skills"].Type() << endl;
 
    //可以用string类型作为下表，读取参数
    string age = "age";
    cout << "age when string is label:" << config[age].as<int>() << endl;
 
    cout << "name:" << config["name"].as<string>() << endl;
    cout << "sex:" << config["sex"].as<string>() << endl;
    cout << "age:" << config["age"].as<int>() << endl;
 
    //读取不存在的node值，报YAML::TypedBadConversion异常
    try{
        string label = config["label"].as<string>();
    }catch(YAML::TypedBadConversion<string> &e){
        std::cout<<"label node is NULL"<<std::endl;
    }//TypedBadConversion是模板类，读取什么类型的参数就传入什么类型
 
 
    cout << "skills c++:" << config["skills"]["c++"].as<int>() << endl;
    cout << "skills java:" << config["skills"]["java"].as<int>() << endl;
    cout << "skills android:" << config["skills"]["android"].as<int>() << endl;
    cout << "skills python:" << config["skills"]["python"].as<int>() << endl;
     // yaml-cpp 中也可以通过迭代的方式，访问 Node 中的内容。
    // 比如，访问 skills 下面的各个元素。
    for(YAML::const_iterator it= config["skills"].begin(); it != config["skills"].end();++it)
    {
        cout << it->first.as<string>() << ":" << it->second.as<int>() << endl;
    }
 
    YAML::Node test1 = YAML::Load("[1,2,3,4]");
    cout << " Type: " << test1.Type() << endl;
 
    YAML::Node test2 = YAML::Load("1");
    cout << " Type: " << test2.Type() << endl;
 
    YAML::Node test3 = YAML::Load("{'id':1,'degree':'senior'}");
    cout << " Type: " << test3.Type() << endl;
 
    ofstream fout("./testconfig.yaml"); //保存config为yaml文件
 
    config["score"] = 99;//添加新元素
 
    fout << config;
 
    fout.close();
 
 
    return 0;
}

#include <fstream>
#include <yaml-cpp/yaml.h>
#include <iostream>
#include <assert.h>
 
int main()
{
    YAML::Node node;  
    assert(node.IsNull());  //初始化的节点是Null类型
    node["key"] = "value";  //当你给它赋值键值对，它转变为Map类型
    //node.force_insert("key", "value");//这个操作和上面等价，但是它不会检查是否存在"key"键，不推荐使用
    if(node["mascot"])
        std::cout << node["mascot"].as<std::string>() << "\n";//单纯的查询操作不会增加一个key，当然上面的if不会执行
 
    node["number"] = 255;
    assert(node.IsMap());   //node是一个Map
    node["seq"].push_back("first element");
    node["seq"].push_back("second element");//node的seq下是Sequence类型，有两个参数
 
    YAML::Node node_2;  
    node_2.push_back("first item");//如果你不给node_2键值对，它是一个sequence类型
    node_2.push_back("second_item");
    node_2.push_back("third_item");
    std::vector<int> v = {1,3,5,7,9};//给node_2插入了一个Sequence
    node_2.push_back(v);
    assert(node_2.IsSequence());//当然，node_2仍然是一个Sequence
 
    assert(node_2[0].as<std::string>() == "first item");
    //对于Sequence类型，你可以使用它的下标来访问
    //注意这里as<T>是一个模板转换，node_2[0]的type是NodeType::Scalar
    auto it = node_2.begin();
    for(; it != node_2.end(); it++)
        std::cout << *(it) << std::endl;
    //当然，你也可以用迭代器来访问
    //他们的类型分别是NodeType::Scalar，NodeType::Scalar，NodeType::Scalar，NodeType::Sequence
    //取值时记得使用as进行模板转换
    node_2["key"] = "value";
    assert(node_2.IsMap());//一旦node_2接收到键值对，它转变为Map类型
    assert(node_2[0].as<std::string>() == "first item");//此时，Sequence时的下标变为它的key值
    node["node_2"] = node_2;//将node_2作为node的一个子项
    node["pointer_to_first_element"] = node["seq"][0];//你也可以给已有的node设置一个别名，类似于一个指针
    assert(node["pointer_to_first_element"].as<std::string>() == "first element");//你可以通过这个指针访问那个node
 
    node.remove(node["seq"][0]);//你可以通过指定一个node来删除它
    node.remove("pointer_to_first_element");//你也可以通过指定key来删除它
}