Key Concepts

Review core concepts you need to learn to master this subject

The Command Line


The command line allows a user to navigate the filesystem and run built-in programs or custom scripts. In Unix, the command line interface is called Bash, and the shell prompt is the $.

List ls


The shell command ls is used to list the contents of directories. If no arguments are given, it will list the contents of the current working directory.

Filesystem Structure


A computer’s filesystem organizes the data stored by a computer, so that it can be easily retrieved by the user. Files are typically represented by a tree-like structure, in which any parent directory can have any number of children.

The root directory is then found at the base of the tree.

Print Working Directory pwd


The shell command pwd displays the file path from the root directory to the current working directory.

cd Change Directory


The shell command cd can be used to move throughout the filesystem of a computer. It accepts a variety of arguments:

  • Full file paths.
  • Names of children of the current directory.
  • .. the parent of the current directory.

Make Directory mkdir


The shell command mkdir can be used to make a new directory in the filesystem according to its argument. If a file path is given, the new directory will be placed at the end. Otherwise, it will create a new directory in the current working directory with the name given.

touch Create New File


The shell command touch creates a new file in the current working directory with the name provided.

Lesson 1 of 1
  1. 1
    The command line is a text interface for your computer. It’s a program that takes in commands, which it passes on to the computer’s operating system to run. From the command line, you can navi…
  2. 2
    What’s going on here? $ ls 2014 2015 hardware.txt 1. In the terminal, fir…
  3. 3
    A filesystem organizes a computer’s files and directories into a tree structure: 1. The first directory in the filesystem is the root directory. It is the parent of all other directories and fil…
  4. 4
    $ pwd /home/ccuser/workspace/blog pwd stands for “print working directory”. It outputs the name of the directory you are currently in, called the working directory. Here the working directo…
  5. 5
    $ cd 2015 1. cd stands for “change directory”. Just as you would click on a folder in Windows Explorer or Finder, cd switches you into the directory you specify. In other words, cd changes the w…
  6. 6
    $ cd jan/memory To navigate directly to a directory, use cd with the directory’s path as an argument. Here, cd jan/memory/ command navigates directly to the jan/memory directory. $ cd .. …
  7. 7
    $ mkdir media The mkdir command stands for “make directory”. It takes in a directory name as an argument, and then creates a new directory in the current working directory. Here we used mkdir t…
  8. 8
    touch keyboard.txt The touch command creates a new file inside the working directory. It takes in a filename as an argument, and then creates an empty file in the current working directory. Her…
  9. 9
    Congratulations! You’ve learned five commands commonly used to navigate the filesystem from the command line. What can we generalize so far? * The command line is a text interface for the comput…

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