File IO Example

• Cout object는 다음과 같은 manipulator를 사용할 수 있다.
• endl : newline 문자를 삽입한 후, 버퍼를 flush한다.
• ends : null문자를 삽입한다
• flush : 출력 버퍼를 flush한다

• 폭지정 (width)
• 출력되는 항목에 폭을 지정하기 위해서는 setw 조작자를 <<와 함께 사용하거나, width 멤버함수를 호출한다.

• #include <iostream.h>

  
  

  int main(void)

  {

      double values[] = {1.23, 35.36, 653.7, 4358.24};

      cout << "|";

      for(int i=0; i<10; i++)

          cout << i;

      for(i=0;i<4;i++)

      {

          cout<<"|";

          cout.width(10);

          cout.fill('*');

          cout << values[i]<<endl;

      }

  }

  |0123456789
  |******1.23
  |*****35.36
  |*****653.7
  |***4358.24

  
  

  
  

  File IO Class

  • ifstream : file stream class for input
  • ofstream : file stream class for output
  • fstream : file stream input output

  File Open

  ofstream outfile("test.dat");

  ofstream outfile; outfile.open("test.dat");

  Check file Open

  If(!outfile)      //fail open file else    //success

  If(!outfile.is_open())    //fail to open file else   //success

  File Close

  Outfile.close()

  ifstream infile("test.dat"); if(!inflie) cout << "Not opended test.dat"; else cout << "Opened test.dat";

  Example : this program open test.txt file input mode, and read the file, display the result to stdout and save to test.out

  #include <iostreamh.>

  #include <fstream.h>

  #include <iomanip.h>

  #define SIZE 256

   

  int main(void)

  {

  int nCntChars, nCntWords, nCntLines;

  char buffer[SIZE], ch;

   

  //create input file stream

  ifstream infile("test.txt", ios::in|ios::nocreate);

   

  //create output file stream

  ofstream outfile("test.out");

  if(!infile || !outfile){

  cerr << "Fail to open!!\n";

  return -1;

  }

   

  //count input character numbers

  for(nCntChars = 0; infile.get(ch); ++nCntChars); //nCntChars -> number of total characters

   

  infile.clear();        //EOF reset

  infile.seekg(0L, ios::beg);        //move to beginning of file

   

  //count of input words

  nCntWords = 0;

  while(infile >> buffer)        ++nCntWords;

   

  infile.clear();        //EOF reset

  infile.seekg(0L, ios::beg);        //move to beginning of file

   

  //copy

  for(nCntLines = 1; infile.getline(buffer, SIZE); ++nCntLines)        //nCntLines-1 -->total line

  {

  cout.width(3);

  cout << nCntLines << "  ";

  cout << buffer << endl;

  outfile << buffer << endl;

  }

  cout << "Total" << --nCntLines << "line, " << nCntWords << " words, " << nCntChars << endl;

   

  infile.close();

  outfile.close();

  return 0;

  }