Array of Strings to Output File

Question

I am writing a C++ code in which I have dynamically created an array of strings. I have written functions to output both the number of items in the string array as well as the array itself. The next thing I wanted to do is stored the elements of the array in a text file, but when I open the file I have written to, only the last element of the array shows up. Here is a sample of what I am doing:

int num_elem = ReadNumElem(); // my function that gets the number of elements in the array of strings

string *MyStringArray = ReadNames(num_elem); // my function that reads a file and outputs the necessary strings into the array

for(int i = 0; i < num_elem < ++i) {
    ofstream ofs("C:\\Test\\MyStrings.txt")
    ofs << MyStringArray[i] << endl; // I also tried replacing endl with a "\n"
}

I am new to C++, so I apologize if this is too simple, but I have been searching for some time now, and I can't seem to find a solution. The first two functions are not relevant, I only need to know how to output the data into a text file so that all the data shows up, not just the final element in the array. Thanks!

The simple answer is that you should specify std::ios_base::app as a flag in your mode argument to the ofstream constructor, e.g. std::ofstream ofs("C:\\Test\\MyStrings.txt", std::ios_base::out | std::ios_base::app); — obataku
– obataku, Commented Aug 8, 2012 at 20:11
The answer that will help you in the long run is to open the file once outside the loop. — obataku
– obataku, Commented Aug 8, 2012 at 20:11

user438383 · Accepted Answer · 2021-12-12 16:06:26Z

3

You are opening the file every time in the array and overwriting its contents.

Try:

ofstream ofs("C:\\Test\\MyStrings.txt");    
for(int i = 0; i < num_elem ; ++i) {
            
    ofs << MyStringArray[i] << endl; // I also tried replacing endl with a "\n"
}
ofs.close();

edited Dec 12, 2021 at 16:06

user438383

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answered Aug 8, 2012 at 20:09

Rocky Pulley

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Comments

Bowler · Accepted Answer · 2012-08-08 20:16:08Z

1

You need to declare the file outside of the loop

edit

Sorry I didn't mean to answer in one line but it has been done now anyway.

edited Aug 8, 2012 at 20:16

answered Aug 8, 2012 at 20:07

Bowler

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