I want to input some contents to a file, but I'd like to check first if a file with the name I wish to create exists. If so, I don't want to create any file, even if the file is empty.
My attempt
bool CreateFile(char name[], char content[]){
std::ofstream file(name);
if(file){
std::cout << "This account already exists" << std::endl;
return false;
}
file << content;
file.close();
return true;
}
Is there any way to do what I want?
C++17, cross-platform: Using std::filesystem::exists
and std::filesystem::is_regular_file
.
#include <filesystem> // C++17
#include <fstream>
#include <iostream>
namespace fs = std::filesystem;
bool CreateFile(const fs::path& filePath, const std::string& content)
{
try
{
if (fs::exists(filePath))
{
std::cout << filePath << " already exists.";
return false;
}
if (!fs::is_regular_file(filePath))
{
std::cout << filePath << " is not a regular file.";
return false;
}
}
catch (std::exception& e)
{
std::cerr << __func__ << ": An error occurred: " << e.what();
return false;
}
std::ofstream file(filePath);
file << content;
return true;
}
int main()
{
if (CreateFile("path/to/the/file.ext", "Content of the file"))
{
// Your business logic.
}
}
The easiest way to do this is using ios :: noreplace
.
you can also use Boost.
boost::filesystem::exists( filename );
it works for files and folders.
And you will have an implementation close to something ready for C++14 in which filesystem should be part of the STL (see here).
I just saw this test:
bool getFileExists(const TCHAR *file)
{
return (GetFileAttributes(file) != 0xFFFFFFFF);
}
As of C++17 there is:
if (std::filesystem::exists(pathname)) {
...
Try this (copied-ish from Erik Garrison: https://stackoverflow.com/a/3071528/575530)
#include <sys/stat.h>
bool FileExists(char* filename)
{
struct stat fileInfo;
return stat(filename, &fileInfo) == 0;
}
stat
returns 0
if the file exists and -1
if not.
Looked around a bit, and the only thing I find is using the open
system call. It is the only function I found that allows you to create a file in a way that will fail if it already exists
#include <fcntl.h>
#include <errno.h>
int fd=open(filename, O_WRONLY | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
if (fd < 0) {
/* file exists or otherwise uncreatable
you might want to check errno*/
}else {
/* File is open to writing */
}
Note that you have to give permissions since you are creating a file.
This also removes any race conditions there might be
Try
ifstream my_file("test.txt");
if (my_file)
{
// do stuff
}
From: How to check if a file exists and is readable in C++?
or you could use boost functions.
Source: Stackoverflow.com