cs197u: a hands on introduction to unix - umass amhersttian/197u/materials/lecture11.pdf · cs197u:...

UNIVERSITY OF MASSACHUSETTS, AMHERST • College of Information and Computer Sciences

CS197U: A Hands on Introduction to Unix

Lecture 11: WWW and Wrap up

Tian Guo University of Massachusetts Amherst – CICS

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• Assignment 4 was graded and scores on Moodle

• Assignment 5 was due and you can stop the cron jobs after 10 emails ‣ I will grade it this weekend. And those who have more than 45

(including attendance) will have flexibility for the remaining assignments.

• Assignment 6 is due Oct 29; please start early!

• Assignment 7 is going to post soon!

Reminders

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• How to access to your website? ‣ http://www-edlab.cs.umass.edu/~USERNAME/index.html

• How to modify your website? ‣ Default path is under your home directory: ~/public_html ‣ By default, index.html already exists there

• What else could you put inside ~/public_html? ‣ Everything you want others to see

Goal: Set up your personal website (EdLab)

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http://www-edlab.cs.umass.edu/~%3CUSERNAME%3E/index.html




• Copy through command line (Mac/Linux) ‣ scp filename [email protected]:~/public_html

• Copy using WinSCP (Windows) ‣ Connect to elnux4.cs.umass.edu and drag the file

• How do others see it? ‣ Assuming we have a new file “empty.html” ‣ URL: http://www-edlab.cs.umass.edu/~USERNAME/empty.html

Putting stuffs into public_html

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mailto:[email protected]

http://elnux4.cs.umass.edu





• What permissions to set for files in public_html? ‣ What happens if empty.html is set to 600?

‣ Make it visible: set to 755 or 644 - Chmod 755 empty.html Or Chmod 644 empty.html

Control the permission

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• A markup language of tags that can create a webpage in couple lines

<html>

<body>

<!- - This is a comment - - >

This is a webpage.

</body>

</html>

HTML: HyperText Markup Language

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• Paired Tags: Opening and closing tag ‣ Headings of different sizes: h1~h6: <h1> Heading1 </h1> ‣ Start paragraph: <p> A Paragraph </p> ‣ Hyperlink: <a href=“http://www.google.com/“>link_to_Google</a>

- Link to your email: replace “http://URL” by “mailto:[email protected]”

• Unpaired Tags ‣ Reference Image: <img src=“myPhoto.jpg" width=“60" height=“90“/> ‣ Line Breaker: <br> ‣ Horizontal line: <hr>

Tags

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• Code

• Result

Heading Tags

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• Code

• Result

Paragraph Tag

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• Code

• Result

Hyperlink

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• Code

• Result

Image Tag

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• Code

• Results

br Tag

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• Code

• Result

hr Tag

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• Code Academy: HTML & CSS ‣ https://www.codecademy.com/tracks/web

• w3school ‣ http://www.w3schools.com/

More Resources

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https://www.codecademy.com/tracks/web


• xargs: commonly used in pipe to convert multiple lines into single-line argument list

• Example 1: Check out xargs by itself ‣ ls -1 data/ | xargs ‣ Converts output into one line

‣ Why is it useful?

The last but very useful command

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elnux4 tian) > ls -1 data/ | xargs data-1.txt data-2.txt data-3.txt


• Combine it with find: filters out a list of finds and perform some actions

• Do things for all python files (including subdirectories) ‣ find . -name “*.py” | xargs wc -l # Counts the lines of the code ‣ find . -name “*.py” | xargs grep “import” # Looks for import package


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• Run command on different files without for loop ‣ The for loop way

‣ Get the file name; and invoke command for each file ‣ xargs way: ls -1 data/ | xargs -I {} awk -f avg.awk data/{}


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for file in data/* do echo $file awk -f avg.awk $file done


• Using the command line:

• Reading files

• Editing files

cd mv rmmkdir pwd ls

head tail catless more grep

vim awk sed

What we’ve learned

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• Using pipes

• Using output redirection to save output to a file

• Some special symbols

grep “Romeo” file.txt | head -‐n 100 | tail -‐n 10

grep “Romeo” file.txt > RandJ.txt grep “Juliet” file.txt >> RandJ.txt

../ ./ * &

parent directory

current directory

match all files

run cmd in background

and...

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• OS enforces file permissions for user, group, and world

• chmod command is used to change permissions

• Root user has absolute power, or use sudo

• Package managers can help find and install software

elnux7> ls -‐l -‐rwxr-‐xr-‐x 1 twood grad 97 Feb 21 11:33 script.sh -‐rw-‐r-‐-‐r-‐-‐ 1 twood grad 298 Feb 21 11:22 data.txt

sudo apt-‐get install firefox

Important concepts

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About the filesystem

• The filesystem is hierarchical• Directories can contain files or other directories

• / is the root directory, where the hierarchy begins

• Other important directories to remember:

/bin/ - executable files

/sbin/ - privileged executables

/dev/ - devices

/etc - system configuration

/home/ - user home directories

/lib/ - libraries

/opt/ - third-party software

/sys/ - Kernel, device drivers, etc

/usr/ - Other OS programs and data

/var/ - Logs, databases, rapidly-changing file

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• ps and top to learn about running processes

• Lots of log and system files with OS information

elnux5> ps PID TTY TIME CMD 17786 pts/0 00:00:00 tcsh 17830 pts/0 00:00:00 bash 17832 pts/0 00:00:00 top 17833 pts/0 00:00:00 ps

tail /var/log/messages cat /proc/cpuinfo

How to get system info

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Programming and scripting

• C / C++ tools

• Python, perl, ruby, and many more

• Shell scripting

gcc c compiler

g++ c++ compiler

gdb debugger

make build automator

# Command line arguments: dir=$1

if [ -‐d “$dir” ] then echo “Reading files in $d” else echo “Not a directory” exit fi

for f in $dir/*.csv do awk -‐F “,” ‘{print $3+$4}’ $f done

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• Awk is a scripting language for processing structured data• Log files, experimental results, etc

• Can use on the command line or write in a file:

• Very powerful!

• Often used with grep and pipe• <COMMAND> | grep <KEYWORD> | head –n 10 | awk –F”:” ‘{print $n}’

awk -‐F “,” '{print $2}' data.txt

awk -‐F “,” -‐f script.awk data.txt

awk

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• Version control systems are used to store and track source code• Subversion is an open source version

• Important concepts:• Repository - stores history of all files being tracked

• You never edit these files directly

• Local copy - “check out” files from repository to edit them • Modify the files as you like

• Update - updates your local copies • Detects if another user modified the same file• Attempts to merge changes (only works for text files)

• Commit - sends your versions of the files to the repository • Will only update repository if there are no conflicts

Version Control

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• tar command creates one file that is an archive of other files

• also allows you to compress files

• scp command allows you to copy files to or from a remote machine

• rsync synchronizes files and directory

Working with Files

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• screen : detach/attach to terminal sessions • Useful for running long processes

• ctrl-‐z : Suspend a job

• jobs : Provides status of suspended jobs

• bg : Runs jobs in the background

• fg : Runs jobs in the foreground

• nohup: run jobs in detached manner from terminal

• cron: schedule reoccurring jobs

• nice and renice allow you to control process priority

Managing Processes

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Your network

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ifconfig/if up/if down Information about interfaces

iwconfig/iwlist Wireless connection/association

dhclient Getting an IP address from DHCP server

ping Checking out a remote host

host Resolve the name/IP address of a site

traceroute Tracking a packet’s end-to-end path/delay


Network security and traffic monitoring

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arp Address resolution protocol (IP vs. MAC)

ifstat Real time bandwidth monitoring on all interfaces

iftop Monitoring details of specific interface

ftp/scp (Un)secure file transport

wireshark Packet sniffing


• find - prints the path to a file

• locate – finds system files

• whereis/which - locate a binary file

• diff - compares two files

• sort – sorts a file alphabetically or numerically

• uniq - removes identical adjacent lines

• ‘cd -‐’ - moves to the last directory you were in

• export – declare and export variables

• alias - creates a shortcut to a command for the bash shell

Random useful commands

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• 377 Operating Systems• Learn how the Linux kernel works

• 453 Networking and 491G Networking Lab• Networking protocols, routing configuration

• 365 Digital Forensics• Learn about security and low level forensics

Take some more classes

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cs197u: a hands on introduction to unix - umass amhersttian/197u/materials/lecture11.pdf · cs197u:...

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