I want to create thousands of file with txt extension in c++. Is it possible? I can not imagine how can i do that. If I write some code right here so you can understand what I want.
int main ()
{
ofstream myfile;
myfile.open ("example.txt");
myfile << "Writing this to a file.\n";
myfile.close();
return 0;
}
I want to generate a bulk of txt of files with this method. In addition I want to run these codes inside a for structure. At the end of the operation I must have 10,000 file and these file's names are like example1.txt , example2.txt , example3.txt ... You do not have to write code I just want to know how to do it. You can just share link to some tutorial.
Yes, you can do that. Here are the steps I suggest:
Use a for or a while loop.
In each iteration of the loop construct the name of a unique file by using the loop counter. You can use std::ostringstream or sprintf for that.
Use the code you already have to create a file in each iteration of the loop.
#include <fstream>
#include <iostream>
int main () {
std::ofstream myfile;
for(int i=1;i<=1000;i++){
myfile.open("example" + std::to_string(i) + ".txt");
myfile << "Writing this to a file.\n";
myfile.close();
}
return 0;
}
Related
I want to print some data to a file with a few separate calls. I noticed that the default behaviour for a write overwrites the previously written data.
#include <iostream>
#include <fstream>
using namespace std;
void hehehaha (){
ofstream myfile;
myfile.open ("example.txt");
myfile << "Writing this to a file.\n";
myfile.close();
}
int main () {
for(int i=0; i <3 ; i++){
hehehaha();}
return 0;
}
this code writes only one line Writing this to a file. but what I want is the following:
Writing this to a file.
Writing this to a file.
Writing this to a file.
Open the file in app mode instead myfile.open("example.txt", std::ios_base::app);
The default open mode for ofstream is plain out, which recreates the file from scratch (if the file exists, its contents is truncated).
To append to a file you need to use the app mode, or add the flag ate.
The table in this open reference is quite helpful to understand the open-modes and what they do.
I want to print some data to a file with a few separate calls. I noticed that the default behaviour for a write overwrites the previously written data.
#include <iostream>
#include <fstream>
using namespace std;
void hehehaha (){
ofstream myfile;
myfile.open ("example.txt");
myfile << "Writing this to a file.\n";
myfile.close();
}
int main () {
for(int i=0; i <3 ; i++){
hehehaha();}
return 0;
}
this code writes only one line Writing this to a file. but what I want is the following:
Writing this to a file.
Writing this to a file.
Writing this to a file.
Open the file in app mode instead myfile.open("example.txt", std::ios_base::app);
The default open mode for ofstream is plain out, which recreates the file from scratch (if the file exists, its contents is truncated).
To append to a file you need to use the app mode, or add the flag ate.
The table in this open reference is quite helpful to understand the open-modes and what they do.
This is my first post and I'm fairly new to C++. I am currently looking for a way to save multiple variables to a file (XML or TXT) so it looks like this:
charactername:George
level:5
I would also like to be able to read these and put them into a variable.
Ex:
std::string characterName = "George";
(but it would read George from the line in the file charactername:George)
I have a total of 68 variables (48 strings, 11 ints, and 9 bools) I want in 1 file.
Does anyone know a way to do this or a tutorial they could point me towards? I have found was to save 1 string to a file, but not multiple variables of different types.
I think you should learn how to use a datafile matrix,
But before that here is some basic file management code for you to try use, you'll be able to read in data and recover it based on a structured layout, when recovering your bool data use an implicit conversion to change from a string.
Here are some basic file operations, this will create a txt file that has data on new lines:
// basic file operations
// writing on a text file
#include <iostream>
#include <fstream>
using namespace std;
int main () {
ofstream myfile ("example.txt");
if (myfile.is_open())
{
myfile << "This is a line.\n";
myfile << "This is another line.\n"; // this will for data onto a new line to be read later.
myfile.close();
}
else cout << "Unable to open file";
return 0;
}
How to recover data, this will put the data into a string array which you can then use to recall data from in your code:
// how to retrieve the data:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main () {
string line, data_array[67];
ifstream myfile ("example.txt");
if (myfile.is_open())
{
while ( getline (myfile,line) )
{
data_array[i] = line; i++;
}
myfile.close();
}
else cout << "Unable to open file";
return 0;
}
How to edit data, you'll need to have a function to read in all your variables and rewrite the whole text file as unless each line is exactly the same byte you can not jump directly to it.
To look more into detail you should learn how to use a datafile matrix, here are some nice videos to get you started.:
C++ Tutorial (Reading Rows and Columns from datafile Matrix
Matrix in C++ | Part #1 | simple matrix definition using arrays
How may I add a none fixed text to a .txt file? So that I can add text that I just added by hand to the file.
#include <iostream>
#include <fstream>
using namespace std;
int main () {
int x;
ofstream myfile;
myfile.open ("teksts.txt", ios::app);
myfile << x;
myfile.close();
return 0;
}
Also after the file has added the text to the .txt document, how can I pause the run window so It would say "The file has been updated!" and only after I press enter it would exit?
You cannot write a variable to a file, and then replace it later, just like you can't write a variable to cout, and then replace it later.
If you're looking to open a file, write something to it, and then reopen it later, you'll need to use a unique string of text, and then replace that.
myfile << "ABC %%UNIQUE_STRING%% DEF";
Then later...
string uniqueValue = "%%UNIQUE_STRING%%";
string stringObject;
getline(myfile, stringObject);
stringObject.replace(stringObject.find(uniqueValue), uniqueValue.length(), "New Value");
If you're looking for something automatic, everytime the program runs, (since the above will only work once), you'll have to be more clever. One potential option would be to always write to the same character index, and the same amount of characters.
You need to give x a value before you send it to the file ( currently you are just sending junk value)
myfile.open ("teksts.txt", ios::app);
cout << "Please enter text to write to file: ";
cin >> x;
myfile << x;
Just add a statement like cout<< "The file has been updated!";.
To view the output use getchar();
If you want to overwrite the contents each time you open the file, open it in ios::out mode instead. Currently you are using ios::app.
I would also advise to change x into a string, that way you will be able to save text to it.
I am relatively new to using the boost library for c++ and I am wondering how to open a file using this. My aim is to read from a json file however I do not know how to open the file.
In c++, you can do this
int main () {
ofstream myfile;
myfile.open ("example.txt");
myfile << "Writing this to a file.\n";
myfile.close();
return 0;
}
but how can I do this using boost?
You can use boost::filesystem::ifstream (which works with a boost::filesystem::path instance) or simply use a std::ifstream to read the file.
The actual code depends a lot on your concrete use-case.