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Navigation and Pathing

Learning Objectives

By the end of this section, you should be able to:

  • Use command-line options to inspect files and directories
  • Explain and apply relative versus absolute paths
  • Move through directories and reorganize files with confidence
  • Use wildcards to match multiple files quickly

1. Command Line Options & TAB Completion

Notice the ls command lists the files. However, sometimes we want more information than just what is in a folder. For example, we may want to know file timestamps, file sizes, and user permissions.

To get more information, we will use command line flags which will change the way ls operates. Try running the ls -alh command. 

ls -alh

Understanding the Command:

  • -a: The "a" in the flags will list all files.
  • -l: The "l" means to use the long format.
  • -h: The "h" means to output the file sizes in human readable format, rather than just bytes.

Let's say we want to see if we have any files in our .ssh folder. We can list files in the .ssh folder by typing .ssh after ls to specify we want to list files in that folder.

ls .ssh

Since the .ssh folder is in our home folder, we can use TAB COMPLETION to auto-complete the name. Test this by typing ls .s then press TAB and you will see the rest of the name auto-complete.

Case Sensitivity

Now try typing ls .S and press TAB. Did anything happen? No, this is because in Unix files/folders/commands are CASE SENSITIVE.

2. Relative vs Absolute Pathing

So far, we have only used examples of relative pathing, which means the file/folder path relative to the current directory we are in.

An example of absolute pathing would be the string that got returned when we used the pwd command at the beginning. Notice, the path starts with the / character, which means the root (top) of the computer.

Let's try to list files in the HOME folder using absolute paths and TAB completion. TAB will only complete up until the result has multiple options. For example, if you TAB complete the first letter of your username, it probably won't return anything because there are other users with the same name. You can press TAB twice quickly to have it list the different options.

Let's use relative pathing to list the files above our home folder. In Unix, the .. characters signify up a directory whereas . signifies the current directory. Since I know this is going to be a long list, I can use the -1 option for ls to create a single line list.

ls -1 ..

Relative vs Absolute Paths: Quick Practice

Try each of these and confirm with pwd after each step:

  1. Move into training using a relative path.
  2. Return to your home directory using an absolute path.
  3. List the parent directory using ls -1 ...

3. Changing Directories and Working with Files

In order to change directories, use the cd command. Let's navigate into the training folder we made earlier.

cd training/

Notice that the path on the terminal updated from ~ to ~/training. This helps the user know where they are located on the computer.

Let's make an example file called test.txt using the touch command and then verify it was created with the ls command. Touch will create a new empty file or update the timestamp for a given file.

touch test.txt
ls

Let's rename the file to data.txt using the mv command. The mv command takes two parameters: the source file and the destination file. So, to rename the file test.txt to data.txt, use the following command.

mv test.txt data.txt
ls

Now, we want to organize this folder by putting the data.txt file into a new sub-folder called data. Try to figure out how to do that by using a previous command to create the directory then the mv command to move the data.txt folder into the data folder.

mkdir data
mv data.txt data
ls data/

We can use the tree command to visualize the directory tree.

tree

Wildcards and Globbing

Wildcards let the shell match multiple files at once:

  • * matches zero or more characters
  • ? matches exactly one character
  • [abc] matches a single character from a set

Examples:

ls *.txt
ls data?.txt
ls data[0-9].txt

Mini-Challenge: Organize a Project Folder

Create this structure and verify it with tree:

mkdir -p project/data project/results project/scripts
touch project/data/sample1.txt project/data/sample2.txt
mv project/data/sample1.txt project/results/
tree project

Day 1 Checkpoint 2

Before moving on:

  • You can explain . and ...
  • You can switch between relative and absolute paths.
  • You can move and rename files with mv.