Write char to a file - Read file content - gcount()

[dhilipkumar]

Write char to a file

#include <iostream>
#include <fstream>
using namespace std;

int main(int argc, char *argv[])
{
  char ch;

  if(argc!=2) {
    cout << "Usage: WRITE <filename>\n";
    return 1;
  }

  ofstream out(argv[1], ios::out | ios::binary);

  if(!out) {
    cout << "Cannot open file.\n";
    return 1;
  }

  cout << "Enter a $ to stop\n";
  do {
    cout << ": ";
    cin.get(ch);
    out.put(ch);
  } while (ch!='$');

  out.close();

  return 0;
}


Read file content


#include <iostream>
#include <fstream>
using namespace std;

int main()
{
  ifstream in("test", ios::in | ios::binary);

  if(!in) {
    cout << "Cannot open input file.\n";
    return 1;
  }

  double num;
  char str[80];

  in.read((char *) &num, sizeof(double));
  in.read(str, 14);
  str[14] = '\0'; // null terminate str

  cout << num << ' ' << str;

  in.close();

  return 0;
}

Demonstrate gcount().


#include <iostream>
#include <fstream>
using namespace std;

int main()
{
  ofstream out("test", ios::out | ios::binary);

  if(!out) {
    cout << "Cannot open output file.\n";
    return 1;
  }

  double nums[4] = {1.1, 2.2, 3.3, 4.4 };

  out.write((char *) nums, sizeof(nums));
  out.close();

  ifstream in("test", ios::in | ios::binary);

  if(!in) {
    cout << "Cannot open input file.\n";
    return 1;
  }

  in.read((char *) &nums, sizeof(nums));

  int i;
  for(i = 0; i <4; i++)
    cout << nums[ i ] << ' ';

  cout << '\n';

  cout << in.gcount() << " characters read\n";
  in.close();

  return 0;
}

[dhilipkumar]

Use getline() to read a string that contains spaces


#include <iostream>
#include <fstream>
using namespace std;

int main()
{
  char str[80];

  cout << "Enter your name: ";
  cin.getline(str, 79);

  cout << str << '\n';

  return 0;
}


Demonstrate peek() in ifstream


#include <iostream>
#include <fstream>
#include <cctype>
using namespace std;

int main()
{
  char ch;
  ofstream out("test", ios::out | ios::binary);

  if(!out) {
    cout << "Cannot open output file.\n";
    return 1;
  }

  char str[80], *p;

  out << 123 << "this is a test" << 23;
  out << "Hello there!" << 99 << "sdf" << endl;
  out.close();
 
  ifstream in("test", ios::in | ios::binary);

  if(!in) {
    cout << "Cannot open input file.\n";
    return 1;
  }

  do {
    p = str;
    ch = in.peek();                   
    if(isdigit(ch)) {
      while(isdigit(*p=in.get()))
         p++;
      in.putback(*p);
      *p = '\0';                          // null terminate the string
      cout << "Integer: " << atoi(str);
    }
    else if(isalpha(ch)) {                // read a string
      while(isalpha(*p=in.get())) p++;
      in.putback(*p);                     // return char to stream
      *p = '\0';                          // null terminate the string
      cout << "String: " << str;
    }
    else
      in.get();                        // ignore
    cout << '\n';
  } while(!in.eof());
 
  in.close();
  return 0;
}


Demonstrate seekg().


#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;

int main(int argc, char *argv[])
{
  char ch;

  if(argc!=3) {
    cout << "Usage: LOCATE <filename> <loc>\n";
    return 1;
  }

  ifstream in(argv[1], ios::in | ios::binary);

  if(!in) {
    cout << "Cannot open input file.\n";
    return 1;
  }

  in.seekg(atoi(argv[2]), ios::beg);

  while(!in.eof()) {
    in.get(ch);
    cout << ch;
  }

  in.close();

  return 0;
}

[sankarakrishnan]

Good Concept, but too congested to get an view...give the description and use of this code pls

[dhilipkumar]

thanks for your interest on reply.....

     sure i ll provide you as you want with description...