文件操作

C文件操作：

fopen

/* fopen example */
#include <stdio.h>
int main ()
{
  FILE * pFile;
  pFile = fopen ("myfile.txt","w");
  if (pFile!=NULL)
  {
    fputs ("fopen example",pFile);
    fclose (pFile);
  }
  return 0;
}

fprintf

/* fprintf example */
#include <stdio.h>
int main ()
{
   FILE * pFile;
   int n;
   char name [100];

   pFile = fopen ("myfile.txt","w");
   for (n=0 ; n<3 ; n++)
   {
     puts ("please, enter a name: ");
     gets (name);
     fprintf (pFile, "Name %d [%-10.10s]\n",n,name);
   }
   fclose (pFile);

   return 0;
}

sprintf

/* sprintf example */
#include <stdio.h>

int main ()
{
  char buffer [50];
  int n, a=5, b=3;
  n=sprintf (buffer, "%d plus %d is %d", a, b, a+b);
  printf ("[%s] is a %d char long string\n",buffer,n);
  return 0;
}

sscanf

/* sscanf example */
#include <stdio.h>

int main ()
{
  char sentence []="Rudolph is 12 years old";
  char str [20];
  int i;

  sscanf (sentence,"%s %*s %d",str,&i);
  printf ("%s -> %d\n",str,i);
  
  return 0;
}

C++文件操作：

ostream::write

// Copy a file
#include <fstream>
using namespace std;

int main () {

  char * buffer;
  long size;

  ifstream infile ("test.txt",ifstream::binary);
  ofstream outfile ("new.txt",ofstream::binary);

  // get size of file
  infile.seekg(0,ifstream::end);
  size=infile.tellg();
  infile.seekg(0);

  // allocate memory for file content
  buffer = new char [size];

  // read content of infile
  infile.read (buffer,size);

  // write to outfile
  outfile.write (buffer,size);
  
  // release dynamically-allocated memory
  delete[] buffer;

  outfile.close();
  infile.close();
  return 0;
}

istream::read

// read a file into memory
#include <iostream>
#include <fstream>
using namespace std;

int main () {
  int length;
  char * buffer;

  ifstream is;
  is.open ("test.txt", ios::binary );

  // get length of file:
  is.seekg (0, ios::end);
  length = is.tellg();
  is.seekg (0, ios::beg);

  // allocate memory:
  buffer = new char [length];

  // read data as a block:
  is.read (buffer,length);
  is.close();

  cout.write (buffer,length);

  delete[] buffer;
  return 0;
}