The main difference between a command-line and an icon-based interface is that on a command-line interface, you type in commands that are known to and executed by your machine instead of double-clicking on icons. It may seem counter-intuitive at first, but it's a much more powerful way of getting your computer to do exactly what you want. So don't panic!
/home/username/:%
I will be putting the % sign in front of any shell commands to indicate that you type at the prompt.
To see where in the directory tree you currently are: % pwd
To move into a directory: % cd /path/to/directory
To move to your home directory, no argument to cd is required: % cd
To move up one level in the directory structure: % cd ..
In general, . (single dot) refers to the current directory, and .. (double dot) refers to the directory one level up.
An absolute path to a file always starts at the root: /path/to/file/deep/in/the/tree/file.txt. You can also specify a relative path from your current directory. For example:
% cd /path/to/file/deep/in/the/tree/
% pwd
/path/to/file/deep/in/the/tree
% cd ../../
% pwd
/path/to/file/deep/in
% cd the
% pwd
/path/to/file/deep/in/the
Creating a new directory: % mkdir new_dir_name (absolute or relative path ok).
Listing files including hidden (system) files: % ls -a
Renaming a file: % mv old_file_name.old new_file_name.new
Moving a file to a different place: % mv old_path/old_file_name.old new_path/new_file_name.new
Copying a file to a different place: % cp old_path/old_file_name.old new_path/new_file_name.new
Recursively copying a directory: % cp -r old_path/directory new_path/
Checking a text file's contents inside the shell: % more
filename
You may need to type q (for quit) to get back to the command
line.
To change permissions on a file: % chmod [u|g|a][+|-][r|w|x] filename
The syntax here means that you pick one or more of the letters u (for user), g (for group) or a (for all), one of + (add permissions) or - (remove permissions) and one or more of the letters r (for read), w (for write) and x (for execute). It's wise not to remove your own permissions.
Some things can only be done if you are logged in as root (administrator, superuser), for example, copying executables to /usr/bin. You should really know a lot more than this short introduction before you do things as root, but in general, the command to act as superuser is sudo followed by whatever command you wanted in the first place. This will prompt you for the root password.
If you have installed a new program somewhere other than in a place
known to PATH, you will need to give the shell the absolute path to
the program every time:
% /path/to/command_name
or, if you
are currently in the same directory as your program: %
./command_name
Matches all files (equivalent to simple ls): % ls *
Matches only files starting with "b": % ls b*
Matches only files with a .txt extension: % ls *.txt