Write new lines in a file - C++

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1.00/5 (2 votes)

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i tried to insert new line at the end of the file so that it will not update the file but just insert new line at the end without altering whatever is in the file.
my code is here.

#include<iostream>
#include<fstream>
#include<sstream>
using namespace std;
 
int main()
{
	ofstream file("outputcheck.txt");
	ostringstream oss;
	string name="we most";
	string n="people";
	file<<name << "loves" <<n;
	return 0;
}

What I have tried:

it gives a file with that content but each time file will be updated, i mean whatever in file it goes and write just the above line. can somebody help me out.

Posted 24-Mar-16 16:29pm

Member 12398690

Updated 24-Mar-16 19:48pm

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Sergey Alexandrovich Kryukov 25-Mar-16 1:34am

There is no a single new-line in your code, so what would you expect?
And "just insert new line at the end" is still a way to "update the file" (and, probably, quite pointless)...
Why?
—SA

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PJ Arends · Answer 1 · 2016-03-24T18:09:00

Solution 1

The ofstream constructor has two parameters. The second parameter specifies the open mode and it defaults to 'out'. Change it to 'app' which stands for append.

Posted 24-Mar-16 18:09pm

PJ Arends

Comments

[no name] 26-Mar-16 13:31pm

I don't see a reason to give a one here (without any comment GRRRRRRR!!!). I give my small 5 to compensate this a Little bit.
Bruno

PJ Arends 26-Mar-16 19:28pm

Thanks. I do not reply for the points, but just to give the OP a hint in what I believe is the right direction.

Sergey Alexandrovich Kryukov · Answer 2 · 2016-03-24T19:48:00

Please see my comments to the question. You did not even try to insert or add a new line.

C++ "object-oriented" << stream operators are so inconvenient! But perhaps you have to learn how to work with them. In this style of stream programming, there is and endl manipulator:
endl — C++ Reference[^].

Alternatively, you can simply use "\n" inside one of your strings, as shown here: Basic Input/Output - C++ Tutorials[^].

Now, there is one extremely unpleasant problem: the line separators used in files and strings are platform-dependent. This article provides a pretty comprehensive overview of the problem: Newline — Wikipedia, the free encyclopedia[^].

There are programming systems providing multiplatform facility for using this separator, that's it, they return different strings on different OS, and then you add/return this string, which is not statically defined in your code. For C++, such approach is not typical: if you write "\n", this is always a character with code point 10, and "\r" — 13, that's it.

From the other hand, more and more software products are developed to be tolerant to the kinds of line separator, they "normalize" the. Say, if you read the file as is and feed resulting string to a Windows MessageBox, the message would be shown the same way, even if you use a line separator from some other OS.

—SA