ECS98F-W2

📗 -> Lecture Date: Name

---

HID Website Week 2

🎤 Vocab

❗ Unit and Larger Context

Small summary

✒️ -> Scratch Notes

apt - package manager
ssh - Secure SHell protocol

What can the CLI do?

Instead of using a CLI to do things for us, we interact directly with the system
Shells:

• Windows cmd prmpt
• Python
• Bash
• zsh (macos?) (Unix based, similar to bash)

Companies like Linux, so we need to learn it

Scenario:

• Working with a shared computer without a GUI
  • You’re forced to interact using the CLI
• Working with limited internet resources and need to lookup documentation
  • Lots of info found within bash itself

Pros

• Finer control of the OS
• Finer control over program behaviors
• No layers of GUI’s to traverse through
  • FAST
  • Type a lot faster than you can click

Cons

• Unintuitive
• Does not protect you from yourself

Substituting with the CLI

• Text editor or IDE
  • Read or write files
  • Code compilation or execution
  • Find and replace
• File Explorer
  • Creating files
  • Organizing your project
    Anything you can do with a GUI, you can do with the CLI. Oftentimes you can do more.

Introduction to Bash and the filesystem

nrose@ad3.ucdavis.edu@pc3:~$
nrose - User
ucdavis.pc3 - hos
~ - cur dir
$ - CLI ready to receive cmnds

Filesystem overview

If on ~$, pwd will output /home/[username]. In this case, /home/grant

Types of filepaths:

Absolute

• /home/grant/school

Relative

• ./school
• ../noah

Special Entries:

• ./ - Refers to current dir
• ../ - Refers to the dir one above the current location

Bash Basics

cd <path> - Change Directory. If no args, takes to home directory ~$ = /home/user
ls <path> - List Files. If no args, default to working dir

• Can add a -a flag to see ALL files, including hidden files
  • Might use a hidden files to store preferences and configurations, that we wouldn’t want other people to easily see
  • Other commands also can add flags, like tree that can have a -a flag
• -l is another common flag, and will give a detailed output, with permissions and more
• Flags are combinational and order does not matter
  mkdir <flags> <path(s)> - Make directory
  mv <flags> <sourcePath(s)> <destinationPath> - Move files from source to destinations
• Can also rename files, by moving them
  • mv .sec notSecret
• Can overwrite existing files
  cp <flags> <sourcePath(s)> <destinationPath> - Copy files directories
• Can overwrite existing files
  cat <path> - Checks content
• Displaying files: cat reads and displays the contents of one or more files to the terminal.
• Merging files: cat concatenates (merges) the contents of multiple files into a single output stream.
• Creating new files: cat can create new files by redirecting output to a file.
  rm <flags> <filePath(s) - Remove each file permanently
• Does not remove directories by default
• -r - Remove directories and other content recursively
• -i - Prompt before every removal (y or n)

Continue with Aliases

Aliases

Can substitute an alias name for a command to be run

• Useful if things are too tedious or repetitive
  alias <aliasName>='<commandToRun>
• Can overwrite existing commands as well
  • alias rm='rm -i'
    • Adds the rm flag by default, making it ask for confirmation before deleting
  • alias rm='mv -t ~/.trash'
    • Doesn’t delete, but moves to trash folder

.bashrc file has shell configurations

Interacting with files:

Printing contents of a file to screen:

• cat <flags> <file>
  • Prints file contents to console
• less <flags> <file>
  • Interactive screen to look through
  • / key lets you jump through usages of a word

head <file> - First couple lines
head -n <#> <file> - First # lines
tail <file> - Last couple lines
tail -n <#> <file> - Last # lines

Text Editors

Nano and Vim are the big ones

• Nano is the simple one you used for MAT 22AL
• Vim is Vim

Finding CLI help

man <command>

• Long manual with docs
  tldr <flags> <command>
• Short summary, common flags, etc.

🧪-> Example

🔗 -> Related Word

• Link all related words