in Ubuntu we often have to use vim(text editor) to edit different type of files. here is some command to get familiar with this editor ... type the following on the terminal

vim file_name

to start editing press [Insert] button ... then u can edit the file as usually
to finish editing press [Esc] button
then press [Shift] button + [:] button
if u want to save what u do then press [x] button
or
if u want not to save the changed items then press [q] button + [!] button
then to exit press [Enter] button

actually there are lots of commands to run ... but this are i frequently use .....

to know ins & outs of vim visit this