Basic_Unix_Vim

Basic Unix and Vim Skills

In order to accomplish tasks in any high-performance computing system, you need to know how to navigate through and issue commands in a UNIX or Linux operating system. Unix-based systems operate through the command-line rather than a graphical user interface (GUI). In this challenge, you will learn how to see files, make directories, navigate directories, and manipulate files all without a GUI.

 

The Command Line

The Command Line (also called a command prompt) is a text interface for a computer. It is the place in which you type the commands that will be interpreted and executed by the computer when you enter them.

Below is the command line prompt, you can run programs and navigate through files just like you would with Windows Explorer on Windows or Finder on MacOS.

x-userid@login01.anvil:[~] $

---

This example system has been set up so the x-userid, the login node, and the system are displayed in brackets before the prompt. Some systems will only start with the "$".

---

As an example, print your x-userid by typing whoami into the command line and pressing Enter.

x-userid@login01.anvil:[~] $ whoami
x-userid

 

Work With Directories

You will need to learn to navigate the filesystem in order to find and access your files. The filesystem is a collection of files and directories. 'Directory' is just the UNIX term for 'folders' on Windows.

To put us all in the same starting place, we will issue the cd command. This will take us to our home directory.

Type

x-userid@login01.anvil:[~] $ cd

Then hit return.

The commands in a command line are always executed from the directory you are currently in. You can find out what directory you are currently in with the 'present working directory' command, pwd.

x-userid@login01.anvil:[~] $ pwd
/home/x-userid

You should be in the /home/<x-userid> directory, where <x-userid> is replaced with your userid. This directory is where you will land by default when you first log in on the terminal.

The string with forward slashes like e.g. /home/x-userid is a called a path. If you are not already in this directory, you can use the cd command to navigate here as we will see next.

Use the cd command to 'change directory'. On the command line, type cd followed by the path of the target directory. If pwd does not show that you are in your /home/<x-userid> directory, we can use cd followed by the path to get there.

x-userid@login01.anvil:[~] $ cd /home/x-userid
x-userid@login01.anvil:[~] $ pwd
/home/x-userid

---

Make sure you replace userid with your actual userid. We are just using userid as an example.

---

 

If you have not already cloned the repository, execute git clone https://github.com/purduercac/hands-on-with-anvil/ on the command line to download the 'Hands On With Anvil' repository.

The output should look something like:

x-userid@login01.anvil:[~] $ git clone https://github.com/purduercac/hands-on-with-anvil/
Cloning into 'hands-on-with-anvil'...
remote: Enumerating objects: 1486, done.
remote: Counting objects: 100% (445/445), done.
remote: Compressing objects: 100% (248/248), done.
remote: Total 1486 (delta 222), reused 401 (delta 185), pack-reused 1041
Receiving objects: 100% (1486/1486), 95.52 MiB | 3.26 MiB/s, done.
Resolving deltas: 100% (829/829), done.

Use the ls command to see what files and directories are present in your current directory. You should see something similar to this:

x-userid@login01.anvil:[~] $ ls
hands-on-with-anvil

From here, lets try using cd to get to the Basic_Unix_Vim challenge directory in the hands-on-with-anvil repository.

x-userid@login01.anvil:[~] $ cd ~/hands-on-with-anvil/challenges/Basic_Unix_Vim

This is the path relative to your current directory (which would be /home/<x-userid>). You can also use the absolute path with cd i.e. the path string starting with / is called a absolute path. This will take you to the same directory.

x-userid@login01.anvil:[~] $ cd /home/<x-userid>/hands-on-with-anvil/challenges/Basic_Unix_Vim

Execute pwd to check if you're in the right place, and execute ls to see what files are available in this directory.

x-userid@login01.anvil:[Basic_Unix_Vim] $ pwd 
/home/<x-userid>/hands-on-with-anvil/challenges/Basic_Unix_Vim
x-userid@login01.anvil:[Basic_Unix_Vim] $ ls
images README.md text_file.txt

If you want to go back to where you were, remember the previous path you had and use cd to navigate there. e.g. cd /home/<x-userid> .

x-userid@login01.anvil:[Basic_Unix_Vim] $ cd /home/x-userid
x-userid@login01.anvil:[~] $ pwd
/home/x-userid

Let us now learn how to create a new directory. Now that you are in the Basic_Unix_Vim directory, create a new directory by executing the mkdir command followed by the name of the directory.

For example, create a directory named 'mydirectory' by do the following:

x-userid@login01.anvil:[Basic_Unix_Vim] $ mkdir mydirectory 
x-userid@login01.anvil:[Basic_Unix_Vim] $ ls
images mydirectory README.md text_file.txt

Now we can use that directory to hold files. Lets try using the cp command to "copy" a file to the directory. The format is cp followed by the name of the file to copy as well as the path of the new location where the file needs to be copied to.

Try to copy the file text_file.txt to the newly created mydirectory directory using this command:

x-userid@login01.anvil:[Basic_Unix_Vim] $ cp test_file.txt mydirectory

Remember that specifying the full path for the file or directory will also work.

x-userid@login01.anvil:[Basic_Unix_Vim] $ cp /home/<x-userid>/hands-on-with-anvil/challenges/Basic_Unix_Vim/text_file.txt /home/<x-userid>/hands-on-with-anvil/challenges/Basic_Unix_Vim/mydirectory

You can check the contents of a directory with ls without first using cd to go to that directory, by using ls followed by the path or directory name.

x-userid@login01.anvil:[Basic_Unix_Vim] $ ls mydirectory
text_file.txt

You can see that text_file.txt has been successfully copied to the directory mydirectory.

 

Editing Files

We will now learn to edit files using a command line text editor called Vim. Vim is a standard text editor available on almost all systems where you have to use a command line. It provides the quickest way to view and modify files when you don't have access to graphical text editors that you might be used to.

You should be familiar with the command format by now. To open a file in Vim, execute the vim command with the name of the file. Try to open the file text_file.txt with Vim.

x-userid@login01.anvil:[Basic_Unix_Vim] $ vim text_file.txt

This will open a window that looks like this:

Vim has two main modes, Insert Mode and Normal Mode. When Vim opens a file, it will always open in Normal Mode. To start actually editing the text, you need to enter Insert Mode. To do this, press the letter 'i' on your keyboard. You will see the little indicator on the bottom left appear saying -- INSERT MODE -- as you can see in the image below.

Try typing in some sentences. Once you are done, you need to be able to save and/or exit Vim. To do that, you must first go back to Normal Mode. To go to Normal Mode, press the Escape key or press Control key + [ on your keyboard. You will see the little -- INSERT MODE -- indicator disappear as you can see in the image below.

Once in Normal Mode, you can save by typing on your keyboard :w followed by return. These characters won't appear in the main text but will appear in the bottom left. :w is the command for Vim to 'write' the file to disk, thus saving the file.

You can exit out of Vim and go back to the command line by typing in :q followed by return. If you haven't saved, you will get a warning and Vim won't exit, so make sure you save the file with :w first.

And that should give you the basics you need for UNIX and Vim! Try working through the other challenges in this repository now. If you want more in depth details about using UNIX and Vim, you can find it in the intro_to_unix and intro_to_vim directories in the Foundational HPC Skills repository

Cheatsheet

UNIX

Anything in [square brackets] is optional for that command.

Command	Description
pwd	Print the current directory you are in (your 'present working directory')
cd /path/to/file	Navigate to the directory location given by the path
ls [path or directory]	List the files and directories in your current directory or in the directory specified
mkdir directoryname	Create a new directory in your current directory with the name you give
cp filename /path/to/location	Copy the file to the directory given by the path
vim filename	Open a file in Vim

Vim

Command	Description
i	Enter Insert Mode in order to edit text
Escape or CTRL+[ key	Enter Normal Mode to save the file and quit Vim
:w	(In Normal Mode) Save the file
:q	(In Normal Mode) Quit Vim and go back to the command line