1. Introduction

Please use the following tutorial to familiarize yourself with the UNIX command-line environment. 

The iSchool uses GNU/Linux on our cPanel servers, and has Mac OS and/or Windows on the built-in computers in the classrooms.

The primary resource for this tutorial is “A user guide to the UNIX system,” by Rebecca Thomas and Jean Yates. In order to help users have a thorough understanding of how the UNIX system works, we provide basic information before covering the main commands. If you need a quick guide, please skip the first section. Examples in this tutorial are most often run on the iSchool cPanel on a Mac machine.

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2. Symbols and procedures

2.1. Shell prompt ends with $, % or >

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The shell prompt is printed to signal its readiness to accept your command.

2.2. Command

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The command is the command from a human to a computer. An action (or function) can be performed after calling the command.

2.3. Command line

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The command line is the following characters of the shell prompt $ until you terminate the command line using the Return key.

2.4. Command format

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2.5. Argument

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Argument is the specify additional information to operate on. It usually comes after the command. The brackets [] indicate an optional argument.

2.6. Options

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Each option indicates the possible modification of the original command. It usually appears after the normal command.

2.7. Control characters

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Control characters do not represent a printable character. They are the computer's special interpretation.

To type a control character: Hold the CTRL key and the letter (D for example), then release the CTRL key.

2.8. Space character

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The space character can be typed by pressing the space bar. It is frequently required when typing a command. UNIX command line is picky when it comes to a space character.

Below is the example of a command line without a space character.

With a space character, a command ls and an option -l will show file or directories, size, modified date and time, file or folder name and owner of file and its permission.

Examples

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# is the root (superuser) shell prompt indicating in most system that you become root or login as root.

rm is the command name.

-r is the option.

resume is the argument referring to the folder named resume.

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3. Getting Started

3.1. Login

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Further information about using SSH to connect to the iSchool cPanel can be found on this Web Development Resources page (login required.)

3.2. Logout

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You can officially log out of the cPanel session by typing CTRL + D or exit. You will know you have successfully logged out of the system when you see the displayed message below:

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4. Basic commands

4.1. Shell Basics

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Tab Completion

• A single Tab. The Tab key can be used to complete a command, directory name, or a file name.

• Multiple Tab. The shell will show the available options that you can type.

E.g: Pressing Tab twice after typing python reveals multiple versions of the programming language python that are available from the current shell.

Accessing the previous commands

• CTRL + R: look for the previous commands while typing part of the command
• ↑↑ or ↓↓ : access the log of a number of past commands (usually 500)

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4.2. Files and Directories

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Useful symbols

• ~ – A tidle is used to access your home directory.
• . – A single period is used to refer to the current directory.
• .. – Two periods are used to refer to the directory immediately above the current directory.

Navigating Directories: cd and pwd

cd

• Description

Change directory

• Example

This command below will change the directory to the home directory.

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pwd

• Description

Print Working Directory

• Example

This command below will print the current working directory.

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Manipulating Directories: mkdir and rmdir

mkdir

• Description

creates a directory

• Example

tmp is the new created directory in the ischool directory.

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rmdir

• Description

removes a directory if it is empty

• Example

The use of rmdir removes the created EMPTY tmp directory in the ischool directory.

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Commands for Files: touch, cp, mv, rm, and file

touch

• Description

creates a file if it does not currently exist.

• Example

The ischool directory below contains the oldfile.py. Using touch newfile.py creates a newfile.py file in the directory.

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cp

• Description

creates a copy of a file in another directory and/or with a different name.

• Syntax

• Examples

a) Copy the file newfile.py currently located in the ischool directory, [source file], to the public_html directory, [destination].

b) Creates a copy of newfile.py named newfile-bak.py in the current directory.

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mv

• Description

Moves a file or directory to another location or name. Unlike cp, mv erases the original file after placing the file in a new location/name.

• Syntax

• Examples

E.g: Move newfile.py from current directory, [source], into an existed folder named lis452, [destination], and renames it to main.py.

mv is useful to correct a misspelled filename:

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rm

• Description

removes a file.

• Syntax

• Examples

This command below removes the file newfile-bak.py in the current directory.

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file

• Description

tells you what type of file something is.

• Example

The newfile.py is the Python script.

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4.3. Output Redirection

Redirect stdout >

This redirects stdout to a file. If the file already existed, it would be overwritten with the new file.

• Example

Now you can see the contents of the created file ischool.txt using the cat command.

Append stdout >>

This appends stdout to an existed file instead of replacing contents of that file.

• Example

The ischool.txt file has one existing line cpanel. We append help desk to the ischool.txt file.

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Redirect stdin <

This can be used to get the standard input from the file instead of the keyboard.

• Example

The command sort can be used to sort lines of text files.

a) Manual solution
You need to enter the stdin from the keyboard. First, you need to type the command sort and press Enter. You need to type the lines that you want to sort. Type CTRL + D when you are done.

After pressing CTRL + D, you will see the result underneath the input.

b) Automated solution
Insert the contents to the keyboard can be automated using the file. In this case, we create a file named test.txt and edit the file with an editor. The file test.txt looks like this:

To sort the lines in the file test.txt, we can redirect the input from the file.

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Pipes |

This takes/“pipes” standard output from one program, or process, and sends it to another command’s standard input.

• Example

Using the same test.txt above, we are going to sort the lines in the text file using this command:

In this example, the output of the cat command is the content of the test.txt file. Then, it pipes to sort command as the input. In other words, the sort command uses output of the cat command as the input, and it displays the sorted lines.

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4.4. Working with Text Files

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echo

• Description

Echo the STRING(s) to standard output.

• Syntax

• Examples

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cat

• Description

Concatenate FILE(s), or standard input, to standard output.

• Syntax

• Examples

cat can be a useful command when you need to combine/concatenate multiple text files into a single file. This example shows when two log files are combined into one file named output.log.

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head

• Description

Print the first 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name. With no FILE, or when FILE is -, read standard input.

• Syntax

• Examples

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tail

• Description

Print the last 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name. With no FILE, or when FILE is -, read standard input.

• Syntax

• Examples

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4.5. Working Remotely

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SSH

SSH stands for "Secure Shell." SSH can be used to connect to a remote computer. Most modern operating systems (except Windows) support SSH by default. If you are using Windows, third-party programs such as PuTTY (recommended) or Cygwin give you the ability to use SSH. If you are in a non-Windows environment, pull up a shell, and you’re ready to use ssh.

As we mentioned earlier, you can use SSH to login to the iSchool cPanel.

SCP

SCP stands for "Secure Copy." SCP can be used to copy files to/from a remote machine from/to your local machine using ssh connection. You might need to enter your remote machine password if needed.

• Syntax

The source and destination can be either <username>@<remote host>:<path to file> or <local file>.

• Example

• Copy a local file to the remote machine

The command below can be used if you want to copy the file alloutput from the current local directory to the folder ischool in the remote machine which is your iSchool cPanel.

• Copy a file from a remote machine to the local directory

If you want to copy the file newfile.py from the current remote directory to the folder ischool in the local machine, you can use the command below:

For a Windows user, you can open up a Windows command prompt (NOT PuTTY). Navigate to the folder C:\Program Files (x86)\PuTTY). You can run the pscp command instead of the scp command here.

Example

NOTE: Please remember to use the Tab for completion. 

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For more detailed instructions, utilize the tutorial available on Box.