C + + file read and write

Reading and writing of C + + files 1. Writing files in text mode

#include <iostream>#include <fstream>using namespaceStdintMain () {intAr[] = {1123,123, +, $, the, +,2,3};//Method 1,ios::out meaning is also written in the way open streamOfstream Ofile1 ("./test.txt", ios::out);//Method 2Ofstream Ofile2; Ofile2.open ("./test.txt");if(!ofile1) {//File open failedCerr <<"Open Err"<< Endl; Exit1); } for(inti =0; I <sizeof(AR)/sizeof(int); ++i) {ofile1 << ar[i] <<" "; } ofile1.close ();}

2. Reading documents in text mode

#include <iostream>#include <fstream>usingnamespace std;int main(){  int ar[10];  ifstream ifile("./test.txt",ios::in);  if(!ifile){    "open err" << endl;    exit(1);  }  for(int010; ++i){    //用空格分割读进数组                                                              ifile >> ar[i];  }}

3. Binary mode Write file

#include <iostream>#include <fstream>usingnamespace std;int main(){  int ar[] = {11,232,123123,1223,455,4,4,5,56,4,33};  ofstream ofile("./text2.txt", ios::out | ios::binary);  if(!ofile){    "open err" << endl;  }  ofile.write((charsizeof(ar));  ofile.close();}

4. Binary mode read file

#include <iostream>#include <fstream>usingnamespace std;int main(){  int ar[10];  ifstream ifile("./text2.txt",ios::in | ios::binary);  if(!ifile){    "open err" << endl;  }  ifile.read((charsizeof(ar));  ifile.close();}

5. Read and write files by location

• Read by position in text mode

Assuming the contents of the file: "1 12 222 3232 2232323", each number of bytes is different, not correctly read out the desired.

Workaround, use binary mode to read by location.

#include <iostream>#include <fstream>using namespaceStdintMain () {Ifstream ifile ("./test.txt", ios::in);if(!ifile) {Cerr <<"Open Err"<< Endl; }intIndexintValue while(1) {CIN >> index; IFILE.SEEKG (index, Ios::beg);//Move pointerIFile >> value;                                                                 cout << value << Endl; }                                                                                      }

• Read by position in the binary mode

#include <iostream>#include <fstream>usingnamespace std;  int main(){  ifstream ifile("./test.txt", ios::in | ios::binary);  if(!ifile){    "open err" << endl;  }  int index;  int value;  while(1){    cin >> index;    ifile >> value;    cout << value << endl;  }}

C + + file read and write