Geany is a powerful and lightweight programmer's text editor.
Menu Build → Set Build Commands → Execute Commands:
Configure Build Menu - Geany Wiki
Label: Sort lines
tr [:upper:] [:lower:]
Label: To lower case
tr [:lower:] [:upper:]
Label: To upper case
You can start several instances of Geany, but only the first will load files from the last session [Manual]. To open selected files in a new instance of geany (
-i) like in a new "session":
$ geany -i file1 file2 file3
Storing and opening session files can be done on a project basis. Project Organizer is an extension of Geany's project management displaying a tree of files belonging to the project in the sidebar.