Good day, everyone!
I've started using/learning UNIX recently and the only problem i get, is that I can hardly edit a file from within the script (searching/replacing, extracting, ect.) I've tried vi, ex, ed all of them did only half of job, which means they opened out a file but did not perform any editing or any required operations. Hence, I've got a question:
which editor do i need to use, to be able to perform an editing of a file from the script?

Thank you very much for any suggestions and what's more important explanations