c++のファイル読み書き関数

ヘッダファイル、ネーミングスペース

#include 
using name space std;

 

//  
//    ，                 。
explicit basic_ifstream( const char* filename,
                std::ios_base::openmode mode = ios_base::in );	(2) 	
				
explicit basic_ifstream( const std::string& filename,
                std::ios_base::openmode mode = ios_base::in );	(4) 	(since C++11)
				
explicit basic_ifstream( const std::filesystem::path& filename,
                std::ios_base::openmode mode = ios_base::in );	(5) 	(since C++17)
				
basic_ifstream( basic_ifstream&& other ); 						(6) 	(since C++11)
	
/*
explicit        	https://baike.baidu.com/item/explicit/4941869?fr=aladdin
filename:   char* string& ，        ，           "\\"
mode:   ios_base::openmode，    
	ios::in           （ifstream     ）
	ios::out           （ofstream     ）
	ios::app          
	ios::ate                 
	ios::trunc         
	ios::nocreate（     ）             ，        open()       
	ios::noreplace （     ）            ，   open()            。
	ios::binary              ，       
           ，        
     ：    。  int.   0x40，                  。
	#define _SH_DENYRW      0x10    /* deny read/write mode */         
	#define _SH_DENYWR      0x20    /* deny write mode */      
	#define _SH_DENYRD      0x30    /* deny read mode */         
	#define _SH_DENYNO      0x40    /* deny none mode */       
	#define _SH_SECURE      0x80    /* secure mode */    ，    

*/


/*       */
bool is_open();												(until C++11)
bool is_open() const;										(since C++11)

//           
#include 
#include 
#include 
//this file is called main.cpp
 
bool file_exists(const std::string& str)
{
   std::ifstream fs(str);
   return fs.is_open();
}
 
int main()
{
  std::boolalpha(std::cout);
  std::cout << file_exists("main.cpp")  << '
'
            << file_exists("strange_file") << '
';
}

/*       
basic_istream& getline( char_type* s, std::streamsize count );
	(1) 	
basic_istream& getline( char_type* s, std::streamsize count, char_type delim );
	(2) 

*/
//       
#include 
#include 
#include 
#include 
 
int main()
{
    std::istringstream input("abc|def|gh");
    std::vector<:array>> v;
 
    // note: the following loop terminates when std::ios_base::operator bool()
    // on the stream returned from getline() returns false
    for (std::array a; input.getline(&a[0], 4, '|'); ) {
        v.push_back(a);
    }
 
    for (auto& a : v) {
        std::cout << &a[0] << '
';
    }
}

/*          
basic_istream& read( char_type* s, std::streamsize count );
		
*/

//      
#include 
#include 
#include 
#include 
#include 
 
int main()
{
    // read() is often used for binary I/O
    std::string bin = {'\x12', '\x12', '\x12', '\x12'};
    std::istringstream raw(bin);
    std::uint32_t n;
    if(raw.read(reinterpret_cast(&n), sizeof n))
        std::cout << std::hex << std::showbase << n << '
';
 
    // prepare file for next snippet
    std::ofstream("test.txt", std::ios::binary) << "abcd1
abcd2
abcd3";
 
    // read entire file into string
    if(std::ifstream is{"test.txt", std::ios::binary | std::ios::ate}) {
        auto size = is.tellg();
        std::string str(size, '\0'); // construct string to stream size
        is.seekg(0);
        if(is.read(&str[0], size))
            std::cout << str << '
';
    }
}

リファレンスマニュアル
CPP参考マニュアル中国語https://zh.cppreference.com/w/%E9%A6%96%E9%A1%B5
CPP参考マニュアルhttps://en.cppreference.com/w/