Linux Shell

Chapter 2 of The Linux Command Line covers navigation. The commands explored in this chapter are pwd (print working directory), cd (change directory), and ls (list directory contents). I use cd and ls daily, but I don’t often use pwd. The structure of the Linux filesystem follows the Filesystem Hierarchy Standard (FHS), meaning the filesystem is organized in a tree-like form of directories, which can contain files and other directories. The very base directory is called the root directory.

When working in the terminal emulator, we are always in a directory (usually somewhere in the home directory). This is called the current working directory. The current working directory can be viewed using the print working directory or pwd command. The contents of the current working directory can be viewed by using the list directory contents or ls command. An important note to remember about the ls command is that it is able to be used on any directory, not just the current working directory. To change the current working directory we use the change directory or cd command. The cd command is followed by the path to the target directory that you are wanting to change to. You can specify paths one of two ways; relative or absolute.

Relative paths are just as the name suggests, pathnames that are relative to the current working directory. When working with relative paths there are two special notations that can be used to assist the pathing; . and ... The . notation refers to the current working directory, and the .. notation refers to the parent directory. Absolute paths are pathnames to a location regardless of the current working directory. An absolute path starts with the root directory and follows the layout until the desired directory is reached. An example of an absolute path looks like /etc/systemd/system, where system would be the destination directory.

Some important things to remember are first that names are case sensitive in Linux, so /home/Desktop will be a completely different directory than /home/desktop. Likewise with files, hello.txt will be a different file than Hello.txt. Second there are hidden files and directory that start with a ., such as ~/.ssh/ or ~/.bashrc. Third Linux supports filenames and directories with spaces, but please never embed spaces in names. Save your sanity. Instead I suggest using an underscore or hyphen.

Something that I learned from this chapter is cd -, which changes to the previous working directory. Epic.