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假设您有正确的标题并且正在使用命名空间 std；这在使用 fstream 将字符串输出到某个输出文件方面是否有些正确？我只包含了我的代码的相关文件 API 部分，因为它的整体太长了。我已经包含了 iostream 和 fstream 标头。但是我似乎遇到了一些特殊的错误，我使用 myfile 类或对象的方式。

#include <curses.h>
#include <math.h>
#include "fmttime.h"
#include <sys/time.h>
#include <time.h>
#include <unistd.h>
#include <stdio.h>                      // Needed for the file API
#include <iostream>                     // File API headers for C++
#include <fstream>
using namespace std;

// Enumeration list for the colors of the grid, title, sin and cos waves
enum colors
{
        Gridcolor = 1,
        Titlecolor,
        Sincolor,
        Coscolor,
};

void Sim_Advance(int degrees);          // Function prototype for Phase angle
double Sim_Cos();                       // Function that calculates cos
double Sim_Sin();                       // Function that calculates Sin
char* usage();                          // Function which returns error mssg
static const double PI = (M_PI/180);    // Degrees to radian factor
static double PA = 0;                   // Phase angle
static double x;                        // X dimension of screen
static double y;                        // Y dimension of screen
static int delay1 = 300000;             // 300ms Delay
static int currenty = 0;                // Y index
static const int buffsize = 25;         // Size of the character buffer for time

// Function prototype for frame of plot function
void frame(const char* title, int gridcolor, int labelcolor);

// Function prototype for the symbols that form the plot
void mark(WINDOW* window, char ch, int color, double value);

int main(
        int argc,                       // Number of command line arguements
        char* argv[]                    // String of each command line
        )

{
    initscr();                          // Curses.h initilizations
    cbreak();
    nodelay(stdscr, TRUE);
    noecho();                           // Supress character inputs on screen
    start_color();                      // Enable Bg/Fg colors

    // Color Initializations for the enumeration list

    init_pair(Gridcolor, COLOR_RED, COLOR_BLACK);
    init_pair(Titlecolor, COLOR_GREEN, COLOR_BLACK);
    init_pair(Sincolor, COLOR_YELLOW, COLOR_BLACK);
    init_pair(Coscolor, COLOR_MAGENTA, COLOR_BLACK);


    int keyhit;                         // Holder for the getch command
    int ctr = 1;                        // Exit flag
    int degrees = 10;                   // Interval to be added to phase
    int enablelog = 0;                  // Flag for Logging enable
    int disabletrunc = 0;               // Flag for logging without truncation
    char* outputName = NULL;            // Name of output program

    FILE* pLog;                         // File pointer for O/P write
    getmaxyx(stdscr,y,x);               // Find max x and y values of stdscrn

    // Defining a new window in the terminal for printing the plot

    WINDOW* Window = newwin(y-4, x, 2, 0);

    x = x - 2 - buffsize;               // Move window to allow for timestamp
    scrollok(Window, TRUE);             // Enable scrolling window

    // Title string for the plotter

    char cTitle[] = {"Real time Sine/ Cosine Plot"};

    //  API Code for FILE output
    ofstream myfile (pLog);             //
    int i = 1;                          // Index for how many times getopt needs
                                        // to be called. Starts at 1 to offset
                                        // program call string, without options
    while (i < argc)
    {
        switch (getopt (argc, argv, "ao:"))
        {
                case 'a':
                disabletrunc = 1;
                break;

                case 'o':
                enablelog = 1;
                outputName = optarg;    // Gets the name of textfile

                // Open the file as designated by the user
                // and assign it to the file pointer pLog
                // The following if else statement opens the file for
                // logging in 2 distinct modes, extended and truncation

                if (disabletrunc == 1)
                {
                    pLog = myfile.open (outputName, ios::out | ios::app);
                }
                else
                {

                // Print with truncation

                    pLog = myfile.open (outputName, ios::out | ios::trunc);
                }

                break;

                // Case of error, print usage message

                case '?':
                endwin();
                puts(usage());
                return 0;

                break;

                // No more options on command line

                case -1:
                i = argc;
                break;
        }
        ++i;
    }

    // If only '-a' is enabled then this is still an error case
    // This if statement handles that case

    if (disabletrunc == 1 && enablelog == 0)
    {
        endwin();
        puts("\nWARNING: -a must be used in conjuction with -o FILENAME");
        puts(usage());
        return 0;
    }


        while (ctr == 1)                // This will run the program till
        {                               // exit is detected (CTRL-X)
            usleep(300000);             // Delays program execution
            keyhit = getch();

            frame(cTitle, Gridcolor, Titlecolor);  // Prints out the frame once
           struct timeval tv;
            char buf[buffsize];                    // Buffer being sent to formattime
            gettimeofday(&tv, NULL);               // calling function for epoch time
            formatTime(&tv, buf, buffsize);        // Calling formaTime for timestamp
            wattrset(Window, COLOR_PAIR(Gridcolor));
            wprintw(Window,"%s", buf);
            wrefresh(Window);

            mark(Window,'|', Gridcolor, 0);
            mark(Window,'C', Coscolor, Sim_Cos());
            mark(Window,'S', Sincolor, Sim_Sin());

            // Scroll to next y coordinate

            wmove(Window, currenty, buffsize + x);
            wrefresh(Window);
            wprintw(Window, "\n");
            wrefresh(Window);

            currenty = getcury(Window);


            // Print desired data into the output file

            if (enablelog == 1)
                myfile << buf << Sim_Sin() << Sim_Cos() << endl;
                //fprintf(pLog, "%s, %f, %f\n", buf, Sim_Sin(), Sim_Cos());

            Sim_Advance(degrees);       // Advances PA by "degrees" value (10)


                if (keyhit == 24)
                {
                    ctr = 0;            // Exit flag set
                }

        }

        // Only close the file if file exists to avoid error
        if (enablelog == 1)
        {
            myfile.close(pLog);
            //close(pLog);
        }

    endwin();
    return 0;
}

// This function will provide an usage message and give the user
// a list of acceptable option characters to use with the program
// when a non valid option character is used or used improperly

char* usage()
{
    // String to be printed as the error message

    static char errors[] = {"\nSorry Invalid Option entered\n\n"
                            "Please Enter a Valid Option specifier:\n"
                            "-o FILENAME      Enable logging to specified "
                            "output file: FILENAME\n"
                            "-a          Enable extended logging"
                            " rather than truncated logging\n\n"
                            "Please Note: -a cannot be used without -o"
                            " FILENAME\n"};

    return errors;
}

然后将其打印到文件中我可以这样做吗？

myfile << buf << Sim_Sin() << Sim_Cos() << endl;
myfile.close(pLog);

Sim_Sin() 和 Sim_Cos() 返回双精度值，而 buf 只是一个格式化字符串。我试图在互联网上应用一些资源，但它似乎与我的实现不一致（这显然是错误的）。

这是错误

plot.cc: In function 'int main(int, char**)':
plot.cc:93: error: no matching function for call to 'std::basic_ofstream<char, std::char_traits<char> >::basic_ofstream(FILE*&)'
/usr/include/c++/4.4/fstream:623: note: candidates are: std::basic_ofstream<_CharT, _Traits>::basic_ofstream(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.4/fstream:608: note:                 std::basic_ofstream<_CharT, _Traits>::basic_ofstream() [with _CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.4/iosfwd:84: note:                 std::basic_ofstream<char, std::char_traits<char> >::basic_ofstream(const std::basic_ofstream<char, std::char_traits<char> >&)
plot.cc:117: error: expected ';' before 'pLog'
plot.cc:124: error: void value not ignored as it ought to be
plot.cc:208: error: no matching function for call to 'std::basic_ofstream<char, std::char_traits<char> >::close(FILE*&)'
/usr/include/c++/4.4/fstream:736: note: candidates are: void std::basic_ofstream<_CharT, _Traits>::close() [with _CharT = char, _Traits = std::char_traits<char>]
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1 回答 1

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这几乎肯定是不正确的。

目前，我将忽略其他问题，只解决写作本身。写作本身最明显的问题是你几乎总是想要一些东西来将一个值与下一个值分开。它可以是一个空格、一个逗号、一个制表符、一个换行符，...，但你非常需要一些东西。没有它，基本上不可能弄清楚哪些数字属于哪个数字——例如：1234.56789.876

因此，在写出数据时，您希望在信息之间放置一些可识别的内容：

myfile << buf << "\t" << Sim_Sin() << "\t" <<  Sim_Cos() << endl;

其次，几乎endl是不可取的。许多（大多数？）认为它只是在输出中添加一个换行符，但它也会刷新流。只要你只写一两行数据，这可能无关紧要，但如果你要写很多数据，它会大大降低你的代码速度。

myfile << buf << "\t" << Sim_Sin() << "\t" <<  Sim_Cos() << "\n";

在您确实想要刷新流的相对罕见的情况下，我建议您使用std::flush来明确该意图。

编辑：编辑后，您似乎也在尝试将 iostreams 与 C 样式混合FILE *（例如，尝试打开流，但提供 C 样式FILE *作为参数）。我通常建议选择 C ​​样式FILE *（如果您别无选择）或 iostream（如果可能）并始终坚持使用该样式。像你正在做的那样混合这两者不仅会导致很多混乱，而且在某些情况下也会减慢你的代码（额外的时间来保持两者的协调）。

std::ofstream myfile("name.txt");
myfile << buf << "\t" << Sim_Sin() << "\t" <<  Sim_Cos() << "\n";
于 2013-04-18T02:28:56.240 回答