this one has a ton of features https://github.com/FedeDP/ncursesFM well written and commented C code.

full list of features: https://github.com/FedeDP/ncursesFM/wiki/Getting-Started

just to name a few advanced ones:

* Search support: it will search your string in current directory tree. It can search your string inside archives too.

* Basic print support through libcups.

* Extract/compress files/folders through libarchive.

* Powermanagement inhibition while processing a job (eg: while pasting a file) to avoid data loss.

* Internal udisks2 monitor, to poll for new devices. It can automount new connected devices too. Device monitor will list only mountable devices, eg: dvd reader will not be listed until a cd/dvd is inserted.

* Drives/usb sticks/ISO files (un)mount through udisks2.

* Distro package files installation through packagekit.