在Visual Studio 2010和Windows中使用文件描述符

Question

我有一个C++程序,它接受用户的一些文本并将其保存到文本文件中.以下是该计划的片段:

#include "stdafx.h"
#include <ctime>
#include <fcntl.h>
#include <iostream>
#include <string>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include <Windows.h>

using namespace std;

int file_descriptor;
size_t nob;

int check_file(const char* full_path) //Method to check whether a file already exists
{
    file_descriptor = open(full_path, O_CREAT | O_RDWR, 0777); //Checking whether the file exists and saving its properties into a file descriptor
}

void write_to_file(const char* text) //Method to create a file and write the text to it
{
    time_t current = time(0); //Getting the current date and time
    char *datetime = ctime(&current); //Converting the date and time to string

    nob = write(file_descriptor, "----Session----\n\n"); //Writing text to the file through file descriptors
    nob = write(file_descriptor, "Date/Time: %s\n\n", datetime); //Writing text to the file through file descriptors
    nob = write(file_descriptor, "Text: %s", text); //Writing text to the file through file descriptors
    nob = write(file_descriptor, "\n\n\n\n"); //Writing text to the file through file descriptors
}

该计划有三个主要问题:

1. Visual Studio告诉我它无法打开源文件<unistd.h>(没有这样的文件或目录).

2. 标识符open未定义.

3. 标识符write未定义.

我该如何解决这些问题呢？我在Windows 7平台上使用Visual Studio 2010.我想在我的程序中使用文件描述符.

Answer 1

Visual C++更喜欢这些函数的符合ISO的名称:_open和_write.但POSIX命名open并且write工作得很好.

您需要#include <io.h>访问它们.

除此之外,您的代码没有write正确使用该功能.你似乎认为它是另一个名字printf,POSIX不同意.

这段代码在Visual C++中编译得很好.

#include <time.h>
#include <io.h>
#include <fcntl.h>

int file_descriptor;
size_t nob;

int check_file(const char* full_path) //Method to check whether a file already exists
{
    return open(full_path, O_CREAT | O_RDWR, 0777); // Checking whether the file exists and saving its properties into a file descriptor
}

void write_to_file(const char* text) // Function to write a binary time_t to a previously opened file
{
    time_t current = time(0); //Getting the current date and time

    nob = write(file_descriptor, &current, sizeof current);
}

如果您创建一个unistd.h包含#include <io.h>并将其粘贴到系统包含路径中的文件,那么您将不需要任何代码更改(假设您的代码与POSIX兼容).