std::ifstream::is_open() in C++
Last Updated :
22 Aug, 2024
The std::ifstream::is_open() function in C++ is a member function of the std::ifstream class, which is used to check if a file stream object has successfully opened a file for reading or not. This function returns a boolean value, true if the file stream is open and ready for I/O operations, and false otherwise.
In this article, we will learn the std::ifstream::is_open() function, its syntax, how it works, and provide practical example to demonstrate its use in C++ file handling.
Syntax of std::ifstream::is_open() in C++
fileStream.is_open();
Here, fileStream is an object of the std::ifstream class.
Parameters of std::ifstream::is_open()
The std::ifstream::is_open() function does not take any parameters.
Return Value of std::ifstream::is_open()
The return value of the std::ifstream::is_open() function indicates whether the file stream is open or not.
- It returns true if the file is successfully opened.
- It returns false if the file stream has not successfully opened a file
Example of std::ifstream::is_open() in C++
The example below demonstrates how to use std::ifstream::is_open() in C++ to check if a file was successfully opened. After attempting to open a file with std::ifstream, we use is_open() to verify the success of the operation. Depending on the result, we can proceed with file operations or handle any errors.
C++
// C++ program to use std::ifstream::is_open() in C++ to check if a file was successfully opened.
#include <fstream>
#include <iostream>
using namespace std;
int main(){
// Attempt to open the file "example.txt" for reading
ifstream file("example.txt");
// Check if the file was successfully opened
if (file.is_open()) {
cout << "File opened successfully!" << endl;
// Perform file operations here (e.g., reading from the file)
}
else {
cout << "Failed to open file." << endl;
}
// Close the file to release resources
file.close();
return 0;
}
Output
File opened successfully!
Time Complexity: O(1) as std::ifstream::is_open() simply checks the state of the file stream.
Auxiliary Space: O(1), as it does not require any additional memory allocation.
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