如何从控制台输入将文本写入文件 [英] How to write text to a file from console input

问题描述

我有问题从c文件程序中的控制台输入写入文件

请帮帮我。

I have a problem to write a text into file from the console input in c file program
please help me.

推荐答案

我们的想法是创建一个std :: streambuf的派生，它将数据输出到文件和cout。然后创建它的一个实例并使用cout.rdbuf（...）;



试试这个（http://stackoverflow.com/a/3290886/1758762 [ ^ ]）：

The idea is to create a derivate of std::streambuf which will output data to both the file and cout. Then create an instance of it and use cout.rdbuf(...);

Try this (http://stackoverflow.com/a/3290886/1758762[^]):

class StreambufDoubler : public std::streambuf {
public:
    StreambufDoubler(std::streambuf* buf1, std::streambuf* buf2) :
            _buf1(buf1), _buf2(buf2), _buffer(128)
    {
        assert(_buf1 && _buf2);

        setg(0, 0, 0);
        setp(_buffer.data(), _buffer.data(), _buffer.data() + _buffer.size());
    }

    ~StreambufDoubler() {
        sync();
    }

    void imbue(const std::locale& loc) {
        _buf1->pubimbue(loc);
        _buf2->pubimbue(loc);
    }

    std::streampos seekpos(std::streampos sp, std::ios_base::openmode which) {
        return seekoff(sp, std::ios_base::cur, which);
    }

    std::streampos seekoff(std::streamoff off, std::ios_base::seekdir way, std::ios_base::openmode which) {
        if (which | std::ios_base::in)
            throw(std::runtime_error("Can't use this class to read data"));

        // which one to return? good question
        // anyway seekpos and seekoff should never be called
        _buf1->pubseekoff(off, way, which);
        return _buf2->pubseekoff(off, way, which);
    }

    int overflow(int c) {
        int retValue = sync() ? EOF : 0;
        sputc(c);
        return retValue;
    }

    int sync() {
        _buf1->sputn(pbase(), pptr() - pbase());
        _buf2->sputn(pbase(), pptr() - pbase());
        setp(_buffer.data(), _buffer.data(), _buffer.data() + _buffer.size());
        return _buf1->pubsync() | _buf2->pubsync();
    }

private:
    std::streambuf*     _buf1;
    std::streambuf*     _buf2;

    std::vector<char>   _buffer;
};


int main() {
    std::ofstream myFile("file.txt");
    StreambufDoubler doubler(std::cout.rdbuf(), myFile.rdbuf());
    std::cout.rdbuf(&doubler);

    // your code here

    return 0;
}
</char>

Here is an example (please run the executable from the command line):

#include <stdio.h>
#include <string.h>

int main()
{
  FILE *file;
  int i;
  char firstName[32];
  char lastName[32];
  int found = 0;

  // Open the file for writing
  file = fopen("records.txt", "wt");
  if (!file)
  {
    printf("File could not be opened\n\a\a");
    getchar();
    return -1;
  }

  // Read and save data
  for (i = 0; i < 3; ++i)
  {
    // Read data
    printf("Record #%d\n", i + 1);
    printf("Enter first name: "); scanf("%s", firstName);
    printf("Enter last name:  "); scanf("%s", lastName);
    printf("\n");

    // Save data
    fprintf(file, "%s\t%s\n", firstName, lastName);
  }

  // Close the file
  fclose(file);

  // Open the file for reading
  file = fopen("records.txt", "rt");
  if (!file)
  {
    printf("File could not be opened\n\a\a");
    return -1;
  }

  // Load and display data
  i = 0;
  while(!feof(file) && !found)
  {
    ++i;
    fscanf(file, "%s\t%s", firstName, lastName);
    if (strcmp(firstName, "John") == 0 && strcmp(lastName, "Doe") == 0)
    {
      printf("Record found (#%d): %s %s\n", i, firstName, lastName);
      found = 1;
    }
  }
  if (!found)
    printf("Record could not be found");

  // Close the file
  fclose(file);

  return 0;
}

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