Week6

class: center, middle

# Unix II

.copyright[
<a rel="license" href="http://creativecommons.org/licenses/by/4.0/"><img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by/4.0/88x31.png" /></a>
** [Pat Pannuto](http://patpannuto.com) / Marcus Darden **
]

---

# Big News (1 of 3)

.center[
![Marcus M. Darden, Jr.](img/mmdj.jpg)
]
  - New ~~edition~~ ~~addition~~ guy... Marcus, Jr.
  - Big & Fast

---

# Big News (2 of 3)

.center[
![:scale_img 60%](img/ppannuto-square.jpg)
]
  - C4CS Course Creator
  - Towner Prize (Outstanding GSI) Winner
  - Mr. Chez Betty
  - All around Great Person

---

# Big News (3 of 3)

.center[
![:scale_img 80%](img/mterwil-lecture.png)
]
  - Git II Lecturer: IA Matt Terwilliger
  - Personal redemption
  - \#SEEYOUINCLASS

---

# Administrative

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# Regex/Regexp

## What is it?

- 99 Problems
  - All the "Big" tools use it
  - Try out
    - www.regular-expressions.info
    - www.regexr.com
  - Endless amusement during live demos

## The Basics

- Special Characters `\^$.|?*+()[]{}`
  - Character classes `[<chars>]`
  - Shorthand classes `\<char>` and `[[:class:]]`
  - Anchors
  - Alternation
  - Repetition
  - Greedy & Lazy
  - Grouping
  - Backreferencing

---

# Working on data by line

## Get it out there

- cat
  - echo
  - head
  - tail

## Big Tools

- grep (g/re/p)
  - sed
  - awk

---

# Other Tools

- cut
  - tee
  - tr
  - sort
  - uniq
  - diff
  - comm

---

# 3 Ways to get/use input/output

1. Use pipes (|) to connect multiple commands
  2. Use redirection to read/write files
  3. Use a subshell $() to assign to variables

---

# File Redirection

## File descriptors, name and number

- 0: Standard Input (stdin, cin)
  - 1: Standard Output (stdout, cout)
  - 2: Standard Error (stderr, cerr)

## Operators

- `<` send file as input
  - `>` send output to file (create/overwrite)
  - `>>` append output to file (create/preserve)
  - `>&` merge output
  - `<&` merge input
  - `<<` "Here Document"

---

# Scripts

- Just Do It!
    - `history`
  - Shebang, Hashbang, #!
  - Get that money...
    - `$0` current script
    - `$n` script args 1, 2, 3...
    - `$#` number of args
    - `$*` and `$@` quoted args
    - `$?` the previous return value
  - Variables and Arrays
  - Math... $((EXPRESSION))
  - Spacing
    - Critical
    - Maddening

---

# Control

- Functions

```bash
# Define
function_name() {
  statements
}

# Invoke
function_name

# Delete
unset .f function_name
```

- Loops
    - while (while, do, done)
    - for
    - until
    - select
    - break/continue
  - Conditionals
    - if (if, then, elif, then, else, fi)