Terminal commands

I have some questions about some Terminal commands:

1. Why must you do sudo apt-get update before installing an program or after downloading something? Does it update Ubuntu then?




2. What is the different between sudo gedit /location/to/afile.txt and gksu gedit /location/to/afile.txt?




3. Why people don't use -y on the end of a command, like for example in sudo apt-get install programx -y.




4. What does the -i and -l (are there any more) mean in a Terminal?





5. How can I unpack any .zip or .tar.gz file in a Terminal?

sudo apt-get update updates the repository information of apt, so you can install the latest version of packages.

sudo gedit will ask you for a password in the terminal window, while gksu gedit prompts for a password with a GUI.

Most people like to review any changes they make with root permissions, that's why they refrain from using sudo apt-get -y and similar.

As for -i and -l, these look like parameters you would give to a command. Each command behaves differently and uses different switches, so without knowing the specific command, it's not possible to tell what these mean. Read the manual (man apt-get, for example) or try using --help with any command.

Use unzip file.zip to extract a zip file and tar xzf file.tar.gz to extract a tar.gz file.