- KISS - Focus – high product cohesion - Filter – handle info between objects to limit coupling - Flexibility – allow users to do what they want

Lecture Notes Flashcards by Brendon Newton

scp

Secure copy from one computer to another

How well did you know this?

Not at all

Perfectly

ssh

Secure shell

How well did you know this?

Not at all

Perfectly

OS Structure

Linux, Mac, and Windows have m-nary tree file structures

How well did you know this?

Not at all

Perfectly

Bin folder

Binaries – compiled code

How well did you know this?

Not at all

Perfectly

sudo

Super user do, used to execute a command as an admin of the system

How well did you know this?

Not at all

Perfectly

Tilde expansion

How well did you know this?

Not at all

Perfectly

Characters in filename expansion

- 0 or more characters
  ? - 1 character

How well did you know this?

Not at all

Perfectly

When/where was Unix developed?

At Bell Labs in the 1970s’

How well did you know this?

Not at all

Perfectly

Who is credited with developing Unix?

Alexander Graham Bell

How well did you know this?

Not at all

Perfectly

What language was codeveloped with Unix?

How well did you know this?

Not at all

Perfectly

Notable C developers

Dennis Ritchie, Ken Thompson, Brian Kernighan, Joe Ossanna

How well did you know this?

Not at all

Perfectly

Kernighan

C Bible, written by Ken Thompson and Brian Kernighan

How well did you know this?

Not at all

Perfectly

Principles of Unix

KISS
Focus – high product cohesion
Filter – handle info between objects to limit coupling
Flexibility – allow users to do what they want

How well did you know this?

Not at all

Perfectly

Who created Linux?

Linux Torvalds

How well did you know this?

Not at all

Perfectly

What was Linux written for?

The 80x86 processor

How well did you know this?

Not at all

Perfectly

GNU Definition

GNU’s not Unix

How well did you know this?

Not at all

Perfectly

What was intended to be the standard shell for the GNU system?

Bash

How well did you know this?

Not at all

Perfectly

What does the Kernel do?

Protect and manage resources
Sends messages to the hardware

How well did you know this?

Not at all

Perfectly

What does a shell do?

Interact with the Kernel

How well did you know this?

Not at all

Perfectly

Notable Shell Distros

Redhat, Fedora, Ubuntu, Bash

How well did you know this?

Not at all

Perfectly

What is a distrubution

An OS that includes the Linux kernel and a package management system

How well did you know this?

Not at all

Perfectly

What does the $PATH variable provide?

A list of directories to search whenever we try to execute a command

How well did you know this?

Not at all

Perfectly

opt

Optional

How well did you know this?

Not at all

Perfectly

which

Tells you the path to the executable you are trying to execute

How well did you know this?

Not at all

Perfectly

What is nano?

A text editor

Who developed C?

Dennis Ritchie

C Library Types

Static and Shared

Static C Library

Packaged into the executable and included in every instance of the program

Shared C Library

Pulls the library into the program at runtime so multiple programs can use it at the same time

Linux extension for static libraries

.a (stands for archive)

Linux extension for shared libraries

.so (shared object)

What is problematic about shared libraries?

When they are updated, any program that cannot run with the new one will break

What are Bash programs called?

Bash scripts

Notable shells

- sh (Bourne) - bash (Bourne again shell) - csh (c shell) - ksh (Korn shell, created by David Korn) - zsh (derivative of the csh) - ssh (secure shell)

What does the ssh provide?

Encryption

What port does ssh execute from?

Port 22

What do ports allow?

Ports allow multiple services to run on the same network

What port does telnet execute from?

Port 23

Link types

Hard link and soft link

Soft Link

File tells you where another file is

Hard link

Alias for a file

What kind of links does ln make by default?

Hard links

Reports a snapshot of the current processes

What does export do for variables?

Export makes env variables available to a child of the original shell

What symbols do each type of quote suppress?

" - everything but $, `, \, ! ' - everything

Numbers for stdin, stdout, and stderr

stdin - 0 stdout - 1 stderr - 2

What folder is the trashcan?

dev/nulll

Piping (|)

Takes stdout of one command and redirects it as stdin for the next

What does bash & do?

bash & backgrounds the bash process. This allows you to execute commands in the background while continuing to work in the parent shell

Puts a process back in the foreground

CTRL-d

Indicates the end of a file

lpr

Prints files

lpstat

Shows printers

$SHELL

Tells you where the shell is

lprm

Cancels jobs in the the queue

$PS1

Prompt statement 1

sed

Substitutions in ed

grep

Global regular expression print

awk

Used in this class for cut awk '{ print $1 }' prints the first column

Regex . meaning

Matches any single character

Regex * meaning

0 or more of the previous pattern

Regex [^] meaning

Negates a range

Regex ^ meaning

Anchor to the beginning of a line

Regex $ meaning

Anchor to the end of a line

Regex {n,m} meaning

A range of min,max

Regex + meaning

1 or more of the previous pattern

Regex ? meaning

0 or 1 of the previous pattern

Regex () meaning

Capture groups

$IFS

Internal field separator

Name of the script that is executing

Number of arguments

Process id

Space separated list of parameters

$(cmd)

Command substitution

What value means true in Bash?

0 is true, nonzero is false

Return of the previous command

Numerical vs. String operators

Numerical uses -gt, -lt, -eq, etc. and strings just use the normal operators

set $variable

Sets the list value to the value of $@