Getting Started with Unix Shell

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What is Unix Shell? More importantly, why would you ever need to use it?

Two words. Automation & efficiency. Of course, there are many other pros of Unix and shell, but for me it comes down to automation of repetitive manual tasks and doing so quickly and efficiently.

The Unix Shell is a command-line interface (CLI), that allows users to interact with the operating system. There are many commands and combinations of these commands that make it a powerful tool, today we will cover some of the basic, and essential, commands.

At one point or another, you will have to create, read, update, and delete files and directories. These four operations are commonly referred to as CRUD operations.

Here are the commands you can use to carry out each of these actions:

**Note: When entering commands do not forget to add space or dashes where needed, as it is case and space sensitive. ☺️

Create a new file: touch

melissa$ touch filename

Create, or “make”, a new directory: mkdir

melissa$ mkdir DirectoryNameHere
melissa$ ls ##this command lists all items within current directory
Project 1 Imporant-Files Repo
Icons  learning-commands my-folder
personal-directory index.txt DirectoryNameHere

Read a file: cat

melissa$ cat filename
This would display the content within the file name you named after the command. 

Read the beginning of a file: head

melissa$ head filename 

Read the end of a file: tail

melissa$ tail filename

Read one page at a time: less

melissa$ less filename

Update: nano

melissa$ nano filename

To add or append text to the end of a file: echo

Practice melissa$ echo "Add your string of text here" >> fileName.txt 

#example below, Practice is a directory currently open

Practice melissa$ echo "Hi" >> practice.txt
Practice melissa$ cat practice.txt
Hi

Delete an empty file or directory: rm

$ rm <file or directory name>

Delete a file or directory containing contents: rm -r

$ rm -r directoryname

Other Basic commands:

To “backout” or return to the parent directory of the directory currently open use cd ..

It is important to note that failure to add the space between “cd” and “..” will not change your directory and return a command not found message.

Here is an example when using cd .. to return to the parent directory.

Practice melissa$ cd ..
Documents melissa$  #notice how it is no longer in the "Practice" directory

To print the pathname of the current working directory”

Practice melissa$ pwd
/Users/melissa/Documents/Practice 

To list the contents of the current directory use the ls command.

melissa$ ls 
Project1  Practice  Tutorial my-folder  my-first-repo  index.txt
Icons   Super-Important-Stuff hello-world  Important Files Another-Folder

#Notice how it is listed and compare with the example below.

Very much like learning a new language, putting together a couple keywords together can make things happen. Here a few command combinations to try:

To list the contents of the current directory in a long list use ls -l

Documents melissa$ ls -l
total 8
drwxr-xr-x   2 melissa  staff   64 Feb  7 00:13 Important Files
drwxr-xr-x  12 melissa  staff  384 Feb  5 19:20 Icons
drwxr-xr-x   3 melissa  staff   96 Mar  8 00:43 Practice
drwxr-xr-x   3 melissa  staff   96 Feb 23 23:39 Project1
drwxr-xr-x@  8 melissa  staff  256 Feb 18 18:53 Tutorial
drwxr-xr-x@  8 melissa  staff  256 Feb 17 22:22 hello-world
drwxr-xr-x   6 melissa  staff  192 Feb 18 21:54 Super-Important-Stuff
drwxr-xr-x   2 melissa  staff   64 Feb  6 23:25 Another-Folder
drwxr-xr-x   5 melissa  staff  160 Feb 16 21:43 my-first-repo
drwxr-xr-x   6 melissa  staff  192 Feb 11 00:01 my-folder
-rw-r--r--   1 melissa  staff   45 Feb  7 19:45 index.txt

To list the contents of a directory including hidden files use ls -a

melissa$ ls -a
.   .DS_Store  ..   .localized Project1  Practice  Tutorial my-folder  
my-first-repo  index.txt Icons   Super-Important-Stuff 
hello-world  Important Files Another-Folder
#Notice ..DS_Store and .. .localized, these were the hidden files 

ls lists the contents of the current directory but to list files that were recently changed last use ls -l -rt . The command ls will list the contants, the -l will list it in long form and the -rt will reverse the order of the list and sort it according to its timestamp. This is helpful when you need to quickly identify which file was recently modified.

Documents melissa$ ls -l -rt
total 8

drwxr-xr-x  12 melissa  staff  384 Feb  5 19:20 Icons
drwxr-xr-x   2 melissa  staff   64 Feb  6 23:25 Another-Folder
drwxr-xr-x   2 melissa  staff   64 Feb  7 00:13 Important Files
drwxr-xr-x   5 melissa  staff  160 Feb 16 21:43 my-first-repo
drwxr-xr-x@  8 melissa  staff  256 Feb 17 22:22 hello-world
drwxr-xr-x@  8 melissa  staff  256 Feb 18 18:53 Tutorial
drwxr-xr-x   6 melissa  staff  192 Feb 18 21:54 Super-Important-Stuff
drwxr-xr-x   3 melissa  staff   96 Feb 23 23:39 Project1
drwxr-xr-x   3 melissa  staff   96 Mar  8 00:43 Practice
drwxr-xr-x   6 melissa  staff  192 Mar 22 00:01 my-folder
-rw-r--r--   1 melissa  staff   45 Mar 23 19:45 index.txt

#Notice the difference between this list and the one listed earlier.

To change to a different directory cd

melissa$ cd ~/DirectoryName

# Or 

Documents melissa$ cd Practice
Practice melissa$  
# Notice how it changed from Documents to the Practice Directory.

And for this command, I like to think of it as the “CTRL + F” of shell commands. To search for the occurrences or patterns in a text file or files you can use grep and --color to highlight the occurrences in color.

grep --color "keyword" name-of-file.txt

Practice melissa$ grep --color "puppies" cute-puppies
This afternoon on my drive back home I passed by an animal shelter. 
They had large poster boards advertising puppies up for adoption. I stopped and saw a small play pen filled with small, cute puppies.
I have always wanted to have puppies.That afternoon, 
I went home with 7 puppies 🥰.

There are many, many more, but knowing a few of the basics will go a long way.

Happy learning!