Shell and Git Fun

November 12, 2025 at 06:34 PM EST

Migrating shell and git notes

programming

Intro

Default to shortcuts and be patient with the documentation.

Shell

Terminology

Directory: file that contains pointers (inodes) to other files.

Variables

#${} is useful for adding more characters
name="Joe"; echo ${name} ; echo $name ; echo ${name}_rocks. 

Double quotes("") preserve the content as stored in the variable. Otherwise, it’s processed by the shell.

Arrays:

# In zsh, arrays are 1-indexed
# No commas
words=("Joe" "needs" "to" "breathe")
echo ${words[1]} # Joe
echo ${words[@]} # Joe needs to breathe
echo ${#words[@]} # 4

Conditionals and conditional expressions

# Watch your spaces a
# Double brackets support more operations
# Brackets variations: [[ exp ]], [exp]
# Expressions: -d -a ( exp ), -eq, -ne.
if [ 10 -eq 10 ]; then
    echo "makes sense"
else
    echo "no"
fi

Refer to bracket differences and conditional expressions  

Loops

# while
i=0
count=0
while [[ $i -lt 10 ]]; do
    # (()) is for arithmetic expressions
    (( count++ ))
    (( i++ ))
done
echo "Count: ${count}"

# for
items=("Take" "it" "easy")
for item in $items; do
    echo $item
done

Refer to loops

Commands

man

man command

du

Let’s man du ^1. and decypher the synopsis:

1. You can choose to stick the flags together if they’re inside brackets. All of these are valid:

• du -h -d -k
• du -h -d - k
• du -hd -k

2. Flags with arguments will have underlines next to them. For du, look at depth.

• du -hd1
• du -hd 1

find

The find command took time to understand. I had to understand what primaries exactly meant, but it turns out they’re expressions specific to the find command. An expression is a combination (primaries in this example) of expressions and operators that evaluate to true or false.

1. … means you can repeat the previous argument
2. [expression]: something like -type f

sh

Allows to run a mini-shell script to run more complex commands. It’s useful to create git aliases or embellish certain commands.

sh -c [-abCefhimnuvx] [-o option]… [+abCefhimnuvx] [+o option]… command_string  

What do these commands do?

# You can also write it like: du -h -d -1 
du -hd1 | sort -n

# -type, -name -exec are all primaries
find . -type d -name '202*' -exec rm -r {} \;

find . -type f \( -name "*.aif" -o -name "*.wav" \) -exec mv {} . \;

find . -type d -exec sh -c 'echo "Found {}"' \;

mv *svg* SVG/

Applications

Aliases saves some time to open and boot up projects. These are some of mine:

alias py=/usr/bin/python3
alias refresh='source ~/.zshrc'
alias editshell='vi ~/.zshrc'
alias editgit='vi ~/.gitconfig'
alias nrb='npm run backend'
alias nrd='npm run dev'
alias guitar='cd /Users/kanleafsnail/Desktop/Through/Projects/Python\ Projects/tkinter_music_theory && source .venv/bin/activate && python3 -m package.gui.guitar_gui'
alias diarydb='cd /Users/kanleafsnail/Desktop/Through/Projects/React\ Projects/Diary/diary/backend/instance && sqlite3 diary    .db'
alias ios='open /Users/kanleafsnail/Desktop/Through/Projects/iOS\ Projects/'
alias joe='cd /Users/joesnail/Through/Projects/joefarah/joe-farah && nrd'

The terminal is my motivational speaker.

quotes=(
  "Be more patient when you're looking at documentation, it will save hours."
  "Every line is susceptible to ERROR."
  "How do I even start to think about this?"
  "The hidden secrets of the problem: What can I use?"
  "Do I really know what this function is doing?"
  "What's the initial configuration of my problem?"
  "Do I need more variables, do I need less variables?"
  "Is my order correct?"
  "Are you going too fast?"
  "Is it a logical error, a language error?"
  "Say the English before you say the code"
  "Relax through the edge cases"
  "Sometimes, your initial approach is just plain wrong. Nothing wrong with that. It's just learning."
)

# @: special parameter to access all elements
for q in ${quotes[@]}; do
    echo ${q}
done

# RANDOM's range is 0 - 32767, 
# zsh arrays are 1-indexed: add + 1. 
echo ${quotes[RANDOM % ${#quotes[@]} + 1]}

Counting items in subdirectories

count_items_in_directory() {
  # Prompt user for directory path
  # zsh style read
  read "dir_path?Enter the directory path: "

  # Check if the directory exists
  if [ -d "$dir_path" ]; then
    # List directories under the specified directory with item counts
    find "$dir_path" -mindepth 1 -maxdepth 1 -type d -exec sh -c 'echo "{}: " && find "{}" -mindepth 1 | wc -l' \;
  else
    echo "Directory '$dir_path' does not exist."
  fi
}

• wc -l: number of lines of your result.
• With -mindepth 1 and -maxdepth 1, you don’t count the dir itself.

Modulo practice

practice_mod() {
  while true; do
    # RANDOM % N: [0, n-1]
    a=$(( RANDOM % 41 - 20 ))
    b=$(( RANDOM % 21 - 10 ))
    [[ $b -eq 0 ]] && b=1

    read "answer?What is ${a} mod ${b}? "
    [[ ${answer} == "exit" ]] && break

    result=$(( a % b ))
    [[ ${answer} -eq ${result} ]] && echo "Correct!" || echo "Wrong: ${result}"
  done
}

Creating an .env file with the test command. Use the backslash.

# package.json from Gameok 
# Note: echo \"    \" and  \\n
"create-env": "cd backend && test -f .env || echo  \"SECRET_KEY= #fill\\nADMIN=#fill\\nEMAIL=#fill\\nPASSWORD= #fill\\nDATABASE_URL=sqlite:///gamelibrary.db\\nDATABASE_TRACKING=False\\nFLASK_APP=gameok.py\\nFLASK_ENV=development\\nFLASK_DEBUG=1\" > .env"

Git

Terminology

• Fetch: get the changes from the remote but don’t do anything yet.
• Pull: Fetch and merge.
• Fork: Make a repo on your GitHub Account.
• Clone: Make a copy on your machine.
• Pull Request: Asks the original repo owner to merge your branch into theirs.

Commands

Help

git command --help

Navigation

^(#): parent        # merge commits
~: n commits behind # simply go behind
^..:                # range
c1^..cn             # c1 excluded, cn included.
^2~3                # 2nd parent, go 3 commits behind

Branch Management

git branch -m old new        # Rename branch
git branch -d branch-name    # Checkout the branch first
git checkout -b new-branch   # Create a new branch and move to it
git branch -f main HEAD~3    # Moving a branch pointer

Reset

git reset --soft HEAD~  # undo commit but keep changes staged
git reset --mixed HEAD~ # undo commit and unstage
git reset --hard HEAD~  # working directory changes to the latest commit

Animations: Reset

Merge

# You're on the branch you want feature to be merged with.
git merge feature

Animations: Merge, Conflict, Pull

Rebase

The first argument is always what you’re rebasing to.

# implicit: If I am on branch X
git rebase main
# explicit: I could be anywhere
git rebase main A

Cherry-pick

Plop down a commit from anywhere in the tree onto HEAD (as long as that commit isn’t an ancestor of HEAD).

# Simplest pattern
git cherry-pick commit

Reflog

# Shows where all your head were pointing in the past.
git reflog

# HEAD@{#} <-- number of moves ago
# 144d2b2 HEAD@{1}: commit: Add post 12
# 9fdfd49 HEAD@{2}: commit: Add post 11

Show

# git show [<options>] [<object>…​]
# --pretty and --name-only are options
# <object> here is omitted: the current commit
git show --pretty="" --name-only   # no headers shown

Diff

git diff --pretty="" --name-only 370c264 144d2b2

Remote

git remote add origin url   # Add remote
git remote -v               # Show remote

Revert: creates a new commit that reverse the changes of that commit

git revert commit

Aliases

Creating custom aliases for git.

# shell alias
alias editgit='vi ~/.gitconfig'

# Applies to my system account (whoami)
git config --global --get-regexp alias

# You can have specific configuration for certain projects.
.git/config

# git + alias
# !: treats it as a shell command
[alias]
    st= status
    #cm:  see net block
    cm-no-edit= !git add . && git commit --amend --no-edit
    ptr= push origin main
    f-ptr= push --force origin main
    tree= log --all --graph --decorate --oneline

Fast way to commit  

# Without zsh: you do: read -p 
cm= !zsh -c 'read \"msg?Enter a commit message: \" && git add . && git commit -m ${msg}'

Applications

Rebasing and squashing

git rebase -i HEAD~# # of commits
# interactive menu: squash
git rebase --continue

Squash all commits

# rev-list gives you the commits reachable from where you specify
# $() for shell command
# commit with 0 parent: first one.
git reset --soft $(git rev-list --max-parents=0 HEAD)
git commit -m "What did you do!"

View repository size

# v: verbose  H: human-readable
git count-objects -vH

Removing large files from a git history with git-filter-repo

git filter-repo --path large-file.zip --invert-paths --all
# Accidentally commited large videos 
git filter-repo --path videos.mp4 --invert-paths

Untrack a specific file

git ls-files
git rm --cached filename

Shortcuts

Shell

Vim

Mac

Resources

Git

• Git Branching
• Progit

Footnotes

1. Another man du

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