How to open a file in an existing emacs process from command line?

M-x server-start inside the Emacs session, then use emacsclient -n file1 file2 ... to add files to the existing Emacs. There are additional options you might want to use, e.g. -c to open the files in a new window (frame).

Put (server-start) in your .emacs file.

Add this to ~/.bashrc

alias myedit='emacsclient --alternate-editor="" --no-wait $*' #quotes intentionaly left blank

then use myedit as your editor. You will have to use the -c option to bring up a window.

So you may do this:

myedit -c a-file
run-script #that uses myedit

or

run-script #that uses myedit
myedit -c