Missing Semester IAP 2020

Lecture 1: Shell using Bourne Again Shell

• <date> - shows you time and date
• <echo> - results the string after ‘echo’
• <echo $PATH> - lists all the paths of the computer
• <which echo> - results the path that runs ‘echo’
• Directories
  • <pwd> - print working directory
  • <cd> -change directory
  • <.> - current directory
  • <..> - parent directory
  • <ls> - list files in the directory
  • <ls ..> - list files in a specified directory
  • <cd ~> - goes to your home directory
  • <cd - > - goes to directory you’re previously in
• <ls --help> - list of information about the FILEs
• <ls -l> - gives more information about the files (group owner)
  • Read <ls> - are you allowed to see which files are in this directory
  • Write - are you allowed to rename, create, remove files in this directory
  • Execute <search> - are you allowed to enter this directory
• Changing directories
  • <mv (path from) (path to)> - move files
  • <cp> - copy the file
  • <rm> - remove file
  • <rmdir> - remove a directory if its empty
  • <mkdir> - make a new directory, use quotation marks
• <man ls> - manual page for ls
• Crtl + l - clear
• Making a File with content
  • ’<’ - rewire the input of this program to be the context
  • ’>’ rewire the output of the preceding program into this file

• - pipe, take the output of the program to the left and make it the input of the program to the right

• - last n lines of the input
• Root User
  • User id 0
  • Allowed to do whatever they want
  • <sudo> - super user do
  • <sudo su> - for you to be the administrator

Lecture 2: Shell Tools and Scripting

• <grep> - search in a file
• <echo $(pwd)> - results the current directory
• <ls *.sh> - outputs all files with .sh extension
• <convert image.png image.jpg> - converts images
• <vim script.py>- shows python script
• <man rg> -
• <find . -path ‘**/test/*.py’ -type f> - finds all path with .py file
• <&&> - and operator
• <||> - or operator
• <;> - always true

Lecture 3: Editors (vim)

• Learning a new editor:
  • Start with a tutorial
  • Stick with using the editor for all your text * editing needs
  • Look things up as you go
• Popular editions
  • Visual studio code
  • Vim - popular command-line-based editor
• Operating modes
• Normal - moving around a file and making edits
  • <o> - creates a new line below and goes to insert mode
  • <O> creates a new line above
  • <u> - undo
  • <c-r> - redo (control R)
  • <dw> - deletes a word
  • <de> - deletes end of the word
  • <ce> - change end of the word and goes to insert mode
  • <x> - deletes that character
  • <r> - replaces a character
• Insert - for inserting text <i>
  • Press <esc> to go back to normal mode
  • You can rebind <esc> on your keyboard
  • <c2w> - change word
  • </> - search
• Replace - for replacing text; press <R>
• Visual - for selecting blocks of text; press <v>
  • Line
  • Block; press <c-v>
  • <h><j><k><l> - select a block of text
  • <y> - copy and goes to normal mode
  • <p> - paste
  • <V> - copy lines of text
• Command-line - running a command; press <:>
  • <quit> - quits vim
  • <:w> - writes on the file so you can ‘save’ it
  • <:help :w> - get help for a ‘w’
  • <:qa> - quit all
  • <c-d> -page down
  • <c-u> - page up
  • <fc> - find the first ‘c’ in text
• Customizing Vim
  • plain -text configuration file in ~/.vimrc
• Plug-ins
  • Ack.vim - code search
  • Nerdtree - file tree
  • Vim-easymotion - magic motions

Lecture 6: Version Control (git)

• Root
  • Tree - folder
  • Blob - file
• In Git, history is a directed acyclic graph (DAG) which means that each snapshot in Git refers to a set of “parents”
• “Edits” in new commit history actually create entirely new commits
• A commit has parents, metadata, and the top-level tree
• Reference - pointers to commits and are mutable (can be updated to point to a new commit)
• Git repository - the data objects and references
• <git help <command>> - get help for a git command
• <git log> - shows a flattened log of history
• Branches
  • <git checkout -b <name>> - created a branch and switched to it
  • <git branch> - shows branches
  • <git branch <name>> - creates a branch
  • <git merge <revision>> - merges into current branch
  • <git mergetool> - uses a fancy tool to help resolve merge conflicts
  • <git rebase> - rebase set of patches onto a new base
  • <git stash> - temporarily remove modification to working branch
• Undo a File
  • <git commit --amend> - edits a commit’s contents/message
  • <git reset HEAD <file>> - unstage a file
  • <git checkout -- <file>> - discard changes
• Git Remote
  • <git remote> - list remotes
  • <git remote add <name> <url>> - add a remote
  • <git push <remote> <local branch>:<remote branch> - send objects to remote, and update remote reference
  • <git fetch> - retrieve objects/references from a remote
  • <git pull> - same as git fetch; git merge
  • <git clone> download a repository from remote
• Personal Notes
  • Always update your local files
    • <git checkout master>
    • <git fetch>
    • <git pull --rebase origin master
    • <git checkout -b <name of new branch>>
  • Do some changes on the website
    • <git status>
    • <git add .>
    • <git commit>
      • Ctrl + x, y, enter
    • <git status>
    • <git push origin <name of new branch>>
  • Editing commit history
    • <git stash>
    • <git rebase -i HEAD~2> - changing the last 2 comments
    • Reword your commit
    • <git fetch>
    • <git status>
    • <git log>
      • Press Q
    • <git push origin <name of branch> --force>
    • <git stash>
    • <git stash pop>
  • Here’s a highly recommended reading: Pro Git