Find Maximum Files that Application Can Open on Linux using C++

When developing applications, especially those handling large amounts of data or requiring concurrent access to multiple files, understanding the limits of file handling capabilities is important. This tutorial explains how to find the maximum files that an application can open on Linux using C++.

The provided code begins by initializing a variable count to zero, which will keep track of the number of successfully opened files. It then enters an infinite loop, repeatedly attempting to open the /dev/null file in read-only mode. If the open function fails (returns a value less than zero), the loop breaks; otherwise, it increments the count variable. Finally, the program prints out the value of count, representing the maximum number of files that could be opened before reaching a system-imposed limit.

#include <iostream>
#include <fcntl.h>

int main()
{
    unsigned long count = 0;
    while (true) {
        if (open("/dev/null", O_RDONLY) < 0) {
            break;
        }
        ++count;
    }

    std::cout << count << std::endl;

    return 0;
}

The count will be three less because stdin, stdout, and stderr are already open by default. Output example:

1048573