c++ fstream write to file code example

Example 1: read a file c++

// reading a text file
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main () {
  string line;
  ifstream myfile ("example.txt");
  if (myfile.is_open())
  {
    while ( getline (myfile,line) )
    {
      //use line here
    }
    myfile.close();
  }

  else cout << "Unable to open file"; 

  return 0;
}

Example 2: obj c write file

//writes an textfile to an place in the document directory
-(void)write:(NSString *)dir file:(NSString *)ff{
    //get the documents directory:
    NSArray *paths = NSSearchPathForDirectoriesInDomains
    (NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    
    //make a file name to write the data to using the documents directory:
    NSString *fileName = [NSString stringWithFormat:[@"%@/" stringByAppendingString:dir], 
                          documentsDirectory];
    //creates the content
    NSString *content = ff;
    //save content to the documents directory
    [content writeToFile:fileName 
              atomically:NO 
                encoding:NSStringEncodingConversionAllowLossy 
                   error:nil];
    
}


//usage: [self write:@"text.txt" file:@"this text will be saved"];

Example 3: how to read and write in a file c++

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

ifstream file_variable; //ifstream is for input from plain text files
file_variable.open("input.txt"); //open input.txt

file_variable.close(); //close the file stream
/*
Manually closing a stream is only necessary
if you want to re-use the same stream variable for a different
file, or want to switch from input to output on the same file.
*/
_____________________________________________________
//You can also use cin if you have tables like so:
while (cin >> name >> value)// you can also use the file stream instead of this
{
 cout << name << value << endl;
}
_____________________________________________________
//ifstream file_variable; //ifstream is for input from plain text files
ofstream out_file;
out_file.open("output.txt");

out_file << "Write this scentence in the file" << endl;

Example 4: write to file in C++

ofstream myfile;
myfile.open("file.txt");

myfile << "write this to file"