[SOLVED] How to perform chmod recursively?

Issue

How can I change permissions to 0777, at runtime, of a folder and all its subfolders, recursively?

The code is in c++, mac. I'm including <sys/stat.h> which has chmod, however there's no documentation on how to do it recursively.

Solution

The simplest and most portable way would be to use the std::filesystem library that was added in C++17. In there, you'll find a recursive_directory_iterator and many other handy classes and functions for dealing with filesystem specific things.

Example:

#include <iostream>

#include <filesystem>            // see notes about these two lines at the bottom
namespace fs = std::filesystem;  // -"-

void chmodr(const fs::path& path, fs::perms perm) {
    fs::permissions(path, perm);      // set permissions on the top directory
    for(auto& de : fs::recursive_directory_iterator(path)) {
        fs::permissions(de, perm);    // set permissions
        std::cout << de << '\n';      // debug print
    }
}

int main() {
    chmodr("your_top_directory", fs::perms::all); // perms::all = 0777
}

However, recursive_directory_iterator has an issue when there are too many directories involved. It may run out of file descriptors because it needs to keep many directories open. For that reason, I prefer to use a directory_iterator instead - and collect the subdirectories to examine for later.

Example:

#include <iostream>
#include <stack>
#include <utility>

#include <filesystem>            // see notes about these two lines at the bottom
namespace fs = std::filesystem;  // -"-

void chmodr(const fs::path& path, fs::perms perm) {
    std::stack<fs::path> dirs;
    dirs.push(path);

    fs::permissions(path, perm);

    do {
        auto pa = std::move(dirs.top()); // extract the top dir from the stack
        dirs.pop();                      // and remove it

        for(auto& de : fs::directory_iterator(pa)) {
            // save subdirectories for later:
            if(fs::is_directory(de)) dirs.push(de);
            else fs::permissions(de, perm);
        }
    } while(!dirs.empty());              // loop until there are no dirs left
}

int main() {
    chmodr("your_top_directory", fs::perms::all);
}

You can read about the std::filesystem:: (fs:: in the code above) functions, classes and permission enums used in the example in the link I provided at the top.

In some implementations, with only partial C++17 support, you may find filesystem in experimental/filesystem instead. If that's the case, you can replace the above

#include <filesystem>
namespace fs = std::filesystem;

with the #ifdef jungle I've provided in this answer.

Answered By - Ted Lyngmo

Answer Checked By - Katrina (WPSolving Volunteer)