What's the Fastest Way to Check for File Existence in C ?

Optimizing File Existence Checks in C

Checking the existence of a file is a fundamental operation in programming, especially when working with large sets of files. In C , several methods exist for this task, with different performance characteristics.

To determine the most efficient method, a benchmark was conducted using a test program that ran each method 100,000 times, half on existing files and half on non-existent files. The results (averaged over 5 runs) are summarized below:

Method	Time
ifstream	0.485s
FILE fopen	0.302s
posix access()	0.202s
posix stat()	0.134s

As evident from the results, posix stat() emerges as the fastest method, taking only 0.134 seconds to complete 100,000 checks. This method leverages the stat system call to obtain information about the file, including its existence.

To implement posix stat() in your exist function, you can use the following code:

inline bool exist(const std::string& name)
{
  struct stat buffer;
  return (stat (name.c_str(), &buffer) == 0); 
}

By utilizing posix stat(), you can efficiently verify the existence of files in your C programs. This method is especially valuable when dealing with large file sets, as its speed can significantly reduce overall processing time.

The above is the detailed content of What's the Fastest Way to Check for File Existence in C ?. For more information, please follow other related articles on the PHP Chinese website!