JUNIOR

ACADEMY

8/6/2016

homework

review!

gnu/linux

• What is GNU/Linux?
  • Unix-like OS composed of GNU packages/coreutils and the Linux kernel
• What is GNU?
  • Free and open source software (FOSS) containing the core utilities and basic tools
• What is Linux?
  • Kernel
    • Central core of OS
    • Handles Input/Output requests from software
    • Links software and hardware (CPU)

why use it?

• Privacy
• Free
  • Not just free as in money, but freedom
• Open and shared
• More control
  • ​More direct access to your computer
  • Get to do more cool things
  • You know what you're doing and what's happening
  • No viruses!
• Abundance of different distributions

distros

• Community/company-created OSes using the Linux kernel and a package management system
• When people say they use Linux, they're using a distribution of it
• Differences
  • Package Manager
  • Desktop Environment
  • Default configurations
  • Default packages (software/programs)
  • Release schedule
    • Stable
    • Rolling
  • Logo

package manager

• What is a Package Manager?
  • Collection of software tools that automates installing, configuring, upgrading, and removing packages
  • You don't have to manually install everything
• Each distro has its own package manager
  • Debian-based: apt
  • Arch-based: pacman
  • Red Hat-based: dnf
  • Gentoo-based: portage
• Repositories are servers that contain sets of packages
• sudo apt install sl && sudo apt install cowsay

sudo

• superuser do
• Grants root access for the given command
  • Allows you to configure the files in the root directory (excluding /home)
• Use it when you get the error "permission denied"
• use it ONLY if you know what you're doing
• su
  • su -c == equivalent to sudo
  • su -l == login as given user (root if no argument is passed)

unix files

directories

• Everything is a file or directory; don't need extensions
• / - the root directory, beginning of everything
• /bin - contains binaries (programs) that allow the system to boot and run
• /boot - contains the Linux kernel, initial RAM disk image (to boot), and the boot loader
• /dev - contains device nodes (devices such as USBs, etc)
• /etc - contains system-wide config files & shell scripts that start the system at boot time
• /home - contains user directories
• /lib - contains library files used by core system programs (comparable to Windows' DLLs)

directories

• /lost+found - used in the case of a partial recovery from a filesystem corruption
• /media - contains mount points for removable media tat are automatically mounted (newer systems)
• /mnt - same as /media except for manually mounted media (older systems)
• /opt - used to install optional software (usually commercial)
• /proc - virtual filesystem that tells you how to kernel sees/interacts with your computer
• /root - home directory for root account
• /sbin - contains system binaries for vital system tasks
• /tmp - contains temporary files created by programs
• /usr - contains programs and support files used by regular users (not root)

directories

• /usr/bin - contains executable programs
• /usr/lib - contains shared libraries for /usr/bin programs
• /usr/local - contains programs not included with the distro, but are intended for system-wide use (usually programs compiled from source code)
• /usr/sbin - contains more system administration programs
• /usr/share - contains the shared data used by programs like config files, icons, supplementary files, etc. (Comparable to Windows Program Files)
• /usr/share/doc - contains documentation for packages
• /var - contains data that is likely to change (Ex. databases, spool files, user mail, etc)
• /var/log - contains log files, records of system activity

ubuntu

• In this class, our main OS will be Ubuntu
• Based on Debian
• Beginner-friendly
• Uses Unity as the default DE
• uses .deb files as its packages
  • use the dpkg command to manually install packages downloaded from the internet
  • Ex. dpkg -i chromium-widevine.deb
• Try to use the terminal as much as possible, refrain from using the Ubuntu Software applications

command line interface

• Also known as the terminal
• Gives you complete access/control over your machine
• Use wisely!
  • You don't want to break your system
  • NEVER type in commands if you don't know what they do

apt

• Advanced Package Tool
• apt is the package manager that comes with Debian-based distros
• If you'd like, you can use aptitude, which is like apt, except interactive
  • If you opt to do this, ONLY use apt or aptitude, don't switch between the two or something will break
  • Also, when performing dist-upgrade, do it through apt, not aptitude
• /etc/apt/sources.list determines your sources (repositories)

essential apt commands

• apt search [argument] - searches the apt repo
• apt install [argument] - installs the given package name
• apt remove [argument] - removes the installed package
• apt purge [argument] - completely removes an installed package and its configuration files
• apt autoclean - removes .deb files for uninstalled packages
• apt clean - removes all packages from the package cache
• apt autoremove - removes dependency packages that are no longer needed
• apt update - makes your source list up-to-date
• apt upgrade - upgrades all installed packages 
• apt dist-upgrade - same as above, except uses "smart" conflict resolution

installation time!

• Use what you've learned about apt to install the following software:
  • Chromium
  • Vim
  • Docker
  • Geany
• Remember the rules
  • Only install approved software
  • If there is something you'd like to install, ASK US FIRST
• sudo apt update && sudo apt dist-upgrade

bash syntax

• command -option [argument]
  • The command is the command that Bash executes
    • Ex. cd, touch, mkdir, ls
  • The option is written after a dash (-), it allows you to undergo different ways of executing the command
    • Ex. ls -a     The a option lists all of the files, including hidden ones
    • You can use multiple options at once, a la: pacman -Syu
  • The argument is whatever you're passing into the command
    • Ex. cd Desktop, passes in the Desktop argument to be cd'd into
• Use spaces to separate commands, options, and arguments

more bash

• Wildcards
  • * == any characters
  • ? == any single character
  • [characters] == any character that is a member of the set characters (Ex. :digit:, :lower:, :upper:)
  • Ex. b*.txt == any file beginning with 'b' followed by any characters and ending with '.txt'
• All commands have a standard input (stdin), standard output (stdout), and standard error (stderr)

redirection

• Redirecting standard output
  • command > file
    • ​overwrites/creates the file containing the output of the command
  • command >> file
    • appends the output to the end of the file's contents
• Redirecting standard error
  • command 2> file
    • adding the descriptor '2' makes it redirect an error
    • &> redirects both stdout and stderr
• Dispose of unwanted output by redirecting to /dev/null

redirection

• Redirecting standard input
  • the cat command not only prints the contents of a file, it allows you to concatenate multiple files by using them as arguments
  • if you just type cat alone, you can type something in and that makes it an output until you press Ctrl+D
    • cat > lazy_dog.txt then type something in
    • command < file
      • changes the standard input from keyboard to file

pipelines

• Pipe operator | (vertical bar) pipes the standard output of one command into the standard input of another
• command1 | command2
• Commands used on the pipeline to change the input before outputting it are called filters
  • sort combines multiple outputs into a single, sorted one
    • ls /bin /usr/bin | sort | less
  • uniq omits/reports repeated lines
    • ls /bin /usr/bin | sort | uniq | less
    • ls /bin /usr/bin | sort | uniq -d | less
  • wc prints the number of lines, words, and bytes
  • grep searches a file and prints lines matching a pattern
    • grep "full name" thisIsAFile.py
    • ls /bin /usr/bin | grep zip

exercise

In the terminal, navigate to the exercise1 directory in your Documents/exercises directory

Create an HTML_Files directory

In ONE command, move all of the html files into the HTML_Files directory.

Then, grep through the binDirectoryContents file to find all unique words containing "lib"

python

• What is Python?
• Why are we using Python?

data types

• String
  • "This is a string."
• Boolean
  • True/False
• Integer
  • whole numbers
• Float
  • floating points
• In Python, variables don't need to be typecasted

hello world!

• cd into Documents and make a directory named "python_work", cd into that
• Make a file called "hello_world.py"
• Edit the file and type:
  • print("Hello world!")
• Launch your new program in the terminal!
  • python3 file.py

operators

• +, -, *, /, %, <, >
• Open up your Python interpreter and try it out
  • Ex. Type "python3" into your terminal
  • >>> 5+5*10
• Note: Ctrl+D quits out of the interpreter back into the terminal emulator!

variables

• In the interpreter type in:
  • >>> fred = 100
  • >>> print(fred)
• We just created a variable, called "fred"
• What is the data type of the variable fred?
• A variable is just something that stores value
• A variable varies, and can be reassigned. Try:
  • >>> fred = 200
  • >>> john = fred
  • >>> print(john)

variables

• Variables must follow certain naming conventions
  • NEVER start with a number
  • NO spaces
    • Use underscores or camel casing
  • No special characters (*,.!@#;: etc)
• Syntax:
  • variableName = value
• = vs ==
  • = is assignment
  • == checks equivalency
    • num = 5
    • num == 6

strings

• Anything encased in quotes ("") is a string
• In Python, you just need to put quotes around the value
  • >>> fred = "This is a string"
  • >>> print(fred)
• You can use single quotes
  • Be consistent
  • Use double quotes if there is an apostrophe in the string
• You can concatenate things to a string with +.
  • >>> str = "world!"
  • >>> print("Hello " + str)

tricks with strings

• >>> print(20 * 'abcd')
• A "%" can be a placeholder for values:
  • >>> mytext = 'I am %s years old'
  • >>> print(mytext % 12)
• %s is used in the string, % to assign the value
• Other ways of using it
  • >>> name1 = 'Joe'
  • >>> print('Hello %s, how are you?' % name)
• When using multiple placeholders, use parentheses and commas to separate them
  • >>> print("Hi %s how is %s" % ("Joe"," Jane"))

strings & variables

• DON'T FORGET TO USE QUOTES FOR STRINGS
• If you just put a string without quotes, it'll be read as a variable name
  • Ex. print("Hey Bob") prints the string "Hey Bob"
  • print(Hey Bob) tries to print two variables with the names "Hey" and "Bob"

lists

• You can create a list object if you want to modify or access specific elements in the list
• >>> shopping_list = ['eggs', 'milk', 'cheese']
• >>> print(shopping_list)
• Access items by using brackets and the index
  • Zero based
  • >>> print(shopping_list[2])
  • >>> shopping_list[1] = 'lettuce'
• To add to the end of a list, use .append(element)
  • >>> shopping_list.append('chocolate bar')
  • >>> print(shopping_list)
• Use parentheses instead of brackets to create a tuple
  • ​Tuples are immutable lists
  • >>> t = (1, 2, 3)

range

• You can use the range() function to create a list of numbers
  • Put two numbers in the parentheses to create a list from the first number, to the second number minus 1
    • Ex. range(4, 8) == [4, 5, 6, 7]
  • Put one number in the parentheses to create a list from 0 to the number minus 1
    • Ex. range(5) == [0, 1, 2, 3, 4]

slicing lists

• If you specify the range of indices you want to work with, the list returns only those indices using a colon (:)
• Like the range function, it's the first number to the second number - 1
  • Ex. players = ["Kirk", "Andrew", "Ross", "Jack", "Ian"]
  • player[0:3] == ["Kirk", "Andrew", "Ross"]
• It returns a slice of the list!

exercises

Create three variables containing your first name, last name, and age. Then print a string cohesive sentence using all three.

Ex. "Hello, my name is John Headland and I'm 25 years old."

Create a list of pizza toppings of at least size 5. Print the message "My pizza has these toppings: " followed by the use of a slice to print the last three items of the list

Make a list of 3 people, living or deceased, that you would like to have dinner with. Then you realize your dinner table has grown in size! Append 2 more people to the list.

survey time!

• Using Chromium, please go to the following url:
  • https://www.surveymonkey.com/r/MK3HTPX
• Take the survey