Checking for files with standard C++ is an important task for developers working on file– and directory-related applications. Before transferring any data to disk or attempting to overwrite an existing file, it is vital to check if the file exists. Depending on what the developer is trying to achieve, there are a variety of ways to check if a file exists. This article will teach you more about it. How to check for the existence of files in standard C++
There are numerous methods to find out if a file is there, such as the following
: Using the stat() function Using std::ifstream Using the fopen() function
1: How to check for the existence of files in C++ Using
the stat() function The
- stat()
method
is the most efficient and secure technique for checking for the existence of files. The sys/stat.h header file has a predefined function called stat. The function accepts a path and structure as parameters, where the metadata associated with the file or directory, if any, would be kept. The function returns the result of 0 if the route is legitimate. We would check the existence of the file as an example:
First, the pointer variable FILE stores the file path. After that, the stat header file format is used to initialize the empty structure. The metadata would be saved this way. The stat function is then called inside the if condition. The result would be 0 if the path is correct, meaning the file or directory existed; otherwise, it would be non-zero.
Exit Note
: Make sure to replace the file name “
C_File.txt” with the file name you want to verify
. 2: How to check for the existence of files in C++ Using the std::ifstream() function Using the standard
C++ library function std::ifstream
is
another method of determining whether a file is present. This function returns a stream object that can be used to read the file, which accepts a path as input. To use this function, the developer would pass the path and file name to the constructor of the std::ifstream class. The result of doing this is that the constructor successfully opens the file or that an exception occurs. As a result, if the file is opened, the developer may assume that it is present.
Starting with the main() method, an ifstream class object named file is created to read the target file later. When you invoke the open function on the file object, the name of the target file is provided as an argument. This line will attempt to open the file in read-only mode.
Since a file can only be opened if it physically exists there and cannot be accessed otherwise. We are indirectly using the open() method to verify the existence of the file. Then, using if-else conditional statements, we determine whether the file object has opened the file or not; If you have done so, this means that you are on the specified path and we display a success message; otherwise, an error message occurs.
Output
3: How to Check for the Existence of Files in C++ Using the fopen() function The third way to check if a file exists is to use
the C++
fopen() function
. The fopen() method Creates a stream and opens the file indicated by file name. The mode variable is a string of characters that indicates the type of file access that has been requested. A positional parameter precedes the optional keyword arguments in the mode variable.
We can save the return value of the fopen() execution to the pointer file when it is finished. If the file was successfully opened, the fopen() function, which shows whether the file was previously opened, will produce a file flow pointer that references the destination file. If it was not successful, indicating whether the file was already done, it will return NULL. So if the file reference is not NULL, we know that the file is present and can produce a success message; otherwise, an error message will be sent.
To read the file, we construct a pointer to the FILE class from the main() method. Next, we use the “C_File.txt” and “r” arguments to define the target file and the action we want to perform on it when we execute the fopen() method. ‘r’ indicates that we want to read the file.
Output conclusion
There are different C++ functions to check if a file exists, which are stat, std::ifstream, and fopen. Of the three methods, the stat() function is the fastest and most reliable way to check for the existence of files. While two other functions are also useful to check the existence of the file. Therefore, developers should consider using these features for optimal performance and reliability when checking for the existence of files.
