Let's explore the system.
In this section, we'll learn the basics of moving around the system. Many tasks rely on being able to get to, or reference the correct location in the system. As such, this stuff really forms the foundation of being able to work effectively in Linux. Make sure you understand it well.
The first command we are going to learn is pwd which stands for Print Working Directory. (You'll find that a lof of commands in linux are named as an abbreviation of a word or words describing them. This makes it easier to remember them.) The command does just that. It tells you what your current or present working directory is. Give it a try now.
A lot of commands on the terminal will rely on you being in the right location. As you're moving around, it can be easy to lose track of where you are at. Make use of this command often so as to remind yourself where you presently are.
It's one thing to know where we are. Next we'll want to know what is there. The command for this task is ls. It's short for list. Let's give it a go.
Whereas pwd is just run by itself with no arguments, ls is a little more powerful. We have run it here with no arguments in which case it will just do a plain listing of our current location. We can do more with ls however. Below is an outline of it's usage:
ls [options] [location]
In the above example, the square brackets ( [ ] ) mean that those items are optional, we may run the command with or without them. In the terminal below I have run ls in a few different ways to demonstrate.
Let's break it down:
In the previous commands we started touching on something called a path. I would like to go into more detail on them now as they are important in being proficient with Linux. Whenever we refer to either a file or directory on the command line, we are in fact referring to a path. ie. A path is a means to get to a particular file or directory on the system.
There are 2 types of paths we can use, absolute and relative. Whenever we refer to a file or directory we are using one of these paths. Whenever we refer to a file or directory, we can, in fact, use either type of path (either way, the system will still be directed to the same location).
To begin with, we have to understand that the file system under linux is a heirarchical structure. At the very top of the structure is what's called the root directory. It is denoted by a single slash ( / ). It has subdirectories, they have subdirectories and so on. Files may reside in any of these directories.
Absolute paths specify a location (file or directory) in relation to the root directory. You can identify them easily as they always begin with a forward slash ( / )
Relative paths specify a location (file or directory) in relation to where we currently are in the system. They will not begin with a slash.
Here's an example to illustrate:
You'll find that a lot of stuff in Linux can be achieved in several different ways. Paths are no different. Here are some more building blocks you may use to help build your paths.
So now you are probably starting to see that we can refer to a location in a variety of different ways. Some of you may be asking the question, which one should I use? The answer is that you can use any method you like to refer to a location. Whenever you refer to a file or directory on the command line you are actually referring to a path and your path can be constructed using any of these elements. The best approach is whichever is the most convenient for you. Here are some examples:
After playing about with these on the command line yourself they will start to make a bit more sense. Make sure you understand how all of these elements of building a path work as you'll use all of them in future sections.
In order to move around in the system we use a command called cd which stands for change directory. It works as follows:
If you run the command cd without any arguments then it will always take you back to your home directory.
The command cd may be run without a location as we saw in the shortcut above but usually will be run with a single command line argument which is the location we would like to change into. The location is specified as a path and as such may be specified as either an absolute or relative path and using any of the path building blocks mentioned above. Here are some examples.
Typing out these paths can become tedious. If you're like me, you're also prone to making typos. The command line has a nice little mechanism to help us in this respect. It's called Tab Completion.
When you start typing a path (anywhere on the command line, you're not just limited to certain commands) you may hit the Tab key on your keyboard at any time which will invoke an auto complete action. If nothing happens then that means there are several possibilities. If you hit Tab again it will show you those possibilities. You may then continue typing and hit Tab again and it will again try to auto complete for you.
It's kinda hard to demonstrate here so it's probably best if you try it yourself. If you start typing cd /hTab/<beginning of your username>Tab you'll get a feel for how it works.
Right, now let's put this stuff into practice. Have a go at the following: