Lab III – Linux at UMBC
Overview
 Hello, and welcome to CMSC 201. We will be covering the
following topics in this week's lab:
 TA Introduction:
 My name.
 My email address.
 My office location and office hours.
 The Linux/Unix Environment.
 Exercises:
 Unix Commands. Setup CMSC 201 directories
 Logging Out. How to logout/lock your workstation.
Switching to Python 3.0
 You only need to do this once
 After you’ve logged into gl:
 Type “emacs .cshrc”
 This will open a file with roughly 30 lines of code, scroll to
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

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the bottom and ADD this line on the bottom of the file on
it’s OWN separate line:
 source /afs/umbc.edu/common/etc/python33.cshrc
Save and exit
Log out of gl
Log back in and type “python --version”
Your version should now be 3.3.2
Why Python?
 Very simple, but powerful high level programming
language
 Great for beginners
 Wide variety of applications including ‘throw away’/adhoc programming, scripting, web scripting, XML
processing, and many more
 Far less code when compared to C, Java, etc.
 Very human readable code
Overview
 If you are on a lab computer, you should always be
booted into Linux; otherwise, restart.
 You may bring your own laptop to complete your labs.
However, it is your responsibility to be familiar with
logging into GL and completing the lab.
 If you are using a Mac, simply open the Terminal:
Launchpad  Utilities
General Information
 What good is a TA in this course ?
 Contact Information - Now a Blackboard Tab on the Left
 How are the weekly labs graded ?
 Complete: 3
Incomplete: 2
Not Even Close: 1
Absent: 0
Linux/Unix

There are several flavors of Unix : IRIX, Solaris, Linux, etc. For this class your
programs must run on the gl.umbc.edu machines which run linux. If you are
in the lab and are running linux, when you log into your account you will be
running linux on your own local workstation. The version of linux running in
the labs is exactly the same as the one running on the gl machines. If you are
logging in from another computer that's running linux, like your laptop, when
you ssh into gl.umbc.edu you will be logged onto one of three machines
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linux1.gl.umbc.edu, linux2.gl.umbc.edu, or linux3.gl.umbc.edu
depending on the load of each machine.
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Your directory, where all of your files are stored, can be accessed by all of
the UMBC lab machines as well as by linux1, linux2 and linux3.
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All of the work for this class should be done within your UMBC account.
Resources
 Basic Unix Commands:
http://www.csee.umbc.edu/courses/201/spring12/labs/u
nixcmds.html
 Alphabetical Listing of Linux Commands:
http://www.oreillynet.com/linux/cmd/
 (You would do well to memorize a few, it will make your
life much easier for the duration of this course)
Unix/Linux Commands
 As described in the previous slide, you may run linux
on your local workstation or log onto gl.umbc.edu. For
today's lab we're going to login as you would from
home.
 You'll have to use the ssh command to log
into gl.umbc.edu.
 Right-click on the desktop background to open a
terminal.
 At the linux shell, type ssh gl.umbc.edu.
 Then type your password to login.
Unix/Linux Commands
 ‘cd’ into your 201 directory
 Create a ‘Labs’ directory using ‘mkdir’ folder and ‘cd’
into it
 Create directories for labs 3 through 14
 ‘cd’ into your lab3 directory
lab3.py
 Today, you will create a simple program that combines
the use of integers, math operators, and input/output.
 Start by creating the lab by typing “emacs lab3.py”
which will open up the text editor and a blank file
 Copy the code on the next page, fill in the header with
your name, section number, etc.
 Notice the comments found below main; use them to
give you an idea of how to write your program!
lab3.py

Copy the following code into your newly created file:
# File:
lab3.py
# Written by: YOUR NAME HERE
# Date:
DATE HERE
# Section:
?
# Email:
?@umbc.edu
# Description: Lab 3, i/o and Math operators
def main():
#Prompt for 3 input values
#Casting each input values as integers
#Perform mathematical operations
#Print the totals
main()
lab3.py
 Use the EXACT header example you are given for this lab
for all subsequent labs and homework!
 Your objective in this lab is to create a simple program that
prompts the user for three separate values:
 Upon receiving those values, the values will be stored by
default as strings; cast them into integers
 On the first inputted value, take that value and square it (hint:
use the ‘**’ operator)
 For the second and third values, simply store their sums
 Finally, print out the values, accompanied by appropriate
messages saying what operations were preformed on each
value
Sample Output
To Receive a Full Lab Grade
 Say the name of your TA, his/her office hours, and
where his/her office hours are located
 “Lab3.py” should output the first value entered by the
user squared, and the sum of the second and third
entered values
 Demonstrate that you are running the correct version of
Python (3.3.2) via the command
version”
“python --