These days developers go for heavy text-editors and IDEs like InteliJ, PyCharm, RubyMine, Sublime Text with much more extensions, Vim, Emacs, etc. However, in case of the later two they are not memory and processor heavy however they have very steep learning curves.
On the other hand, GNU Nano come as a life saver. It requires a few MB of RAM(say 3-4 MB) and uses very less CPU resource. Nano is a much powerful tool with much more features.
Default version of Nano in Linux distros have no
--linenumber switch feature. Here is a guide by which you can have one;
Compile Nano from source:
git clone git://git.savannah.gnu.org/nano.git;cd nano;./autogen.sh;./configure;sudo make install
Then add the following to your
# include all the preexisting configs include "/usr/share/nano/*.nanorc" set linenumbers
You can use Meta+# to turn line numbers on and off from within Nano.