helpdesk

Purpose

• Setup environments
• Help find solution to your coding problems
• …

Git

Basics

Before Starting: Configuring git

• Configs
  1. Global use /.gitconfig
  2. Repo specific use .git/config
  3. Repo specific config file will overwrite the global one
• How to view your current config $ git config --list --show-origin
• Config editor $ git config --global core.editor emacs

Git-Basics-Undoing-Things:

• Introduction to undoing changes in Git

• Three basic ways to undo changes in Git:

  • git reset
  • git revert
  • git checkout

• git commit --ammend is your pal for fixing a commit not pushed

• git reset HEAD <file> – Unstage a staged file

• git checkout -- <file> – Discard changes in a file since the last commit

• git revert HEAD – Create a new commit that undoes the changes made in the previous commit

• git push --force origin <branch> – Force push changes to a remote branch that has already been pushed with unwanted changes.

• Reference

What is remote?

Remote on Git refers to a repository that is located on a server or another computer, rather than the user’s local machine. It’s a version of the repository that is used by teams to collaborate on a project. Remote repositories can be accessed and manipulated through Git commands, allowing users to push changes or fetch changes made by others. Remote repositories can be hosted on Git hosting services like GitHub, GitLab, or Bitbucket, or set up on a personal server. Multiple users can access and modify the same remote repository, making it easy for teams to work on a project together.

What is branch?

A branch in Git is a lightweight pointer to a specific commit. It allows developers to work on new features or make changes to the codebase without affecting the main codebase. Branches are created and can be switched between easily, and changes made in one branch do not affect other branches.

To create a new branch in Git, you can use the command git branch <branch_name>. This creates a new branch but does not switch to it, so you will be working in the same branch until you use the command git checkout <branch_name> to switch to the new branch. Alternatively, you can use the command git checkout -b <branch_name> to create and switch to the new branch at the same time.

To end a branch, you can use the command git branch -d <branch_name>. This deletes the specified branch, but only if it has been fully merged into the main branch. If you want to delete a branch whether it has been fully merged or not, you can use the command git branch -D <branch_name>. It’s important to note that once a branch has been deleted, you cannot restore its commit history.

Resources

• Visualization of Commands
• https://ohshitgit.com/
• https://learngitbranching.js.org/?locale=zh_CN
• Missing semester video
• https://git-scm.com/book/en/v2

Julia Package Management

• This section is really well presented by Prof Liu at here and here.
• Ask me anything and let’s do a quick demo.

Shell Tools

Shells

Shell, zsh and bash are all command-line interface (CLI) interpreters used in Unix-like operating systems.

• Shell is the simplest and most basic interpreter. Its primary function is to provide a command-line interface to the system. It can execute scripts, launch programs, manage files and directories, and perform basic system administrative tasks.

• Bash (Bourne-Again SHell) is the default shell on most Linux distributions. It is backward-compatible with the original Bourne shell and includes many additional features, such as command-line editing, job control, and shell scripting capabilities. Bash is widely used as it is both easy to use and has a large user community, resulting in a plethora of available resources (tutorials, scripts, etc.) online.

• Zsh (Z shell) is an extended version of the shell, with a more powerful command-line editing and completion system. It includes features like spelling correction and tab-completion, and it also supports plugins and themes. Zsh is commonly used by power users who require more productivity and efficiency from their command-line interface.

Path Variable

On Linux, the PATH variable is an environment variable that contains a list of directories that the shell searches for executable files. When a user enters a command in the shell, the shell looks for the executable file in each directory listed in the PATH variable, in the order they are listed. The PATH variable can be modified to add or remove directories, and it can also be set on a per-user or system-wide basis. The PATH variable is important because it allows users to easily run programs without having to specify the full path to the executable file each time.

File Permission

In Linux, file permissions determine who can access, edit, and execute files and directories. Each file and directory has three permission settings: owner, group, and other. The owner is the user who created the file or directory, the group is a set of users with specific permissions, and other is anyone else who has permission to access the file or directory. Each permission setting can have three levels of access: read, write, and execute. Read permission allows the user to view the contents of the file or directory, write permission allows the user to edit or delete the file or directory, and execute permission allows the user to run the file or access the directory. File and directory permissions can be changed using the chmod command in Linux.

Common Shell Commands

1. cd - Change directory
2. ls - List directory contents
3. mv - Move or rename files or directories
4. cp - Copy files or directories
5. rm - Remove files or directories
6. mkdir - Create directories
7. rmdir - Remove empty directories
8. touch - Create an empty file or update the modification timestamp of a file
9. cat - Display the content of a file
10. grep - Search for a pattern in files
11. ps - Display information about running processes
12. kill - Terminate a process
13. echo - Print a message to the console
14. chmod - Change permissions of files or directories
15. history - Display a list of recently used commands
16. ssh - Connect to a remote server through ssh protocol
17. scp - Copy files between local and remote machines over ssh protocol
18. tar - Create or extract archive files
19. df - Display information about disk usage
20. wget - Download files from the internet.

Tools

1. ripgrep (rg): A fast text search tool that recursively searches a directory hierarchy for a regex pattern.
2. Tmux: A terminal multiplexer that allows you to divide your terminal into multiple panes and windows.
3. Ncdu: A disk usage analyzer that helps you visualize which files and directories are consuming the most space on your filesystem.
4. tldr: A simplified and community-driven version of man pages that provides practical examples of command line usage.
5. Bat: A cat replacement that provides syntax highlighting, line numbering, and Git integration.
6. Exa: A modern replacement for ls that supports additional features like file icons, Git status, and color themes.
7. Bandwhich: A bandwidth usage analyzer that helps you see which processes are using the most network bandwidth.
8. fd: A more user-friendly alternative to find that allows you to search for files and directories using a streamlined syntax.
9. htop: An interactive process viewer that provides detailed information about system resource usage and allows you to manage processes.
10. Tmuxp: A command line tool that allows you to easily manage and share your Tmux configurations.
11. direnv: direnv is a shell extension that allows users to manage environment variables for different directories. It is designed to alleviate the inconvenience of constantly setting and unsetting environmental variables within different development environments.

Resources

• Shell Script Learning
• The Art of Command Line

Editors

• Vim
• Emacs
• VSCode