💡 学习完这门课程后，我也有了自己的 dotfile repo：https://github.com/yujiachen-y/dotfiles

知道的前提是知道自己不知道什么。

The Missing Semester of Your CS Education

Shell

• Connecting programs
  • < file and > file rewire the input and output streams of a program to a file.
  • >> to append to a file.
  • | chain programs by the output of one is the input of another.
• sysfs exposes a number of kernel parameters as files.
• Conditionally execute commands, && and ||
• Separate commands within the same line ;
• Get the output of a command as a variable.
  • $( CMD ) , directly replace the output in the command.
  • <( CMD ) , execute CMD and place the output in a temporary file and substitute the <() with that file’s name.
• Shell globbing
  • ? and * to match one or any amount of characters.
  • {} expand a series of commands
    • e.g. convert image.{png,jpg}

Special Characters

GitHub - koalaman/shellcheck: ShellCheck, a static analysis tool for shell scripts

Tools

GNU coreutils via Homebrew

• xargs
• man replacement: TLDR
• Finding files fd
• Finding code grep ack ag rg
• Shell finding commands fzf
• Directory Navigation fasd autojump frecency
• View directory structure tree broot nnn ranger
• Stream editor sed , a useful programming language awk (人生苦短，我用Python
• rsync

Job Control

• kill
• Stop a process Ctrl-Z
• Continue the paused job in the foreground or in the background using fg or bg
• jobs
• tmux

Aliases

Note that there is no space around the equal sign =, because alias  is a shell command that takes a single argument.

Dotfiles

GitHub does dotfiles - dotfiles.github.io

Use Git to manage secret content via creating bash functions to encrypt / decrypt secret content into / from Git.

Portability

if [[ "$(uname)" == "Linux" ]]; then {do_something}; fi

# Check before using shell-specific features
if [[ "$SHELL" == "zsh" ]]; then {do_something}; fi

# You can also make it machine-specific
if [[ "$(hostname)" == "myServer" ]]; then {do_something}; fi

# Test if ~/.aliases exists and source it
if [ -f ~/.aliases ]; then
    source ~/.aliases
fi

gitconfig supports including configurations from local files.

[include]
    path = ~/.gitconfig_local

SSH Configuration

• generate a key pair → ssh-keygen
• manage passphrase → ssh-agent gpg-agent

Connecting to GitHub with SSH - GitHub Docs

What’s ssh port forwarding and what’s the difference between ssh local and remote port forwarding

~/.ssh/config

Host vm
    User foobar
    HostName 172.16.174.141
    Port 2222
    IdentityFile ~/.ssh/id_ed25519
    LocalForward 9999 localhost:8888

# Configs can also take wildcards
Host *.mit.edu
    User foobaz

Key based authentication

cat .ssh/id_ed25519.pub | ssh foobar@remote 'cat >> ~/.ssh/authorized_keys'

# Or
ssh-copy-id -i .ssh/id_ed25519 foobar@remote

Copying files over SSH

rsync

ZSH

为什么不使用fish？

因为我对shell不够了解，fish不支持Posix标准，我觉得有很多我不知道的坑。

Editors (Vim)

Know keyboard shortcuts about your most recently used editor!d

The big list of Vim-like software

Keyboard remapping

Karabiner-Elements

GitHub - koekeishiya/skhd: Simple hotkey daemon for macOS

folivora.ai - Great Tools for your Mac!

Daemon & Automation

systemd

# /etc/systemd/system/myapp.service
[Unit]
Description=My Custom App
After=network.target

[Service]
User=foo
Group=foo
WorkingDirectory=/home/foo/projects/mydaemon
ExecStart=/usr/bin/local/python3.7 app.py
Restart=on-failure

[Install]
WantedBy=multi-user.target

cron

Hammerspoon

FUSE

filesystem in user space，对文件系统的中间抽象，用来加上远程、分布式、加密等功能。

• sshfs - Open locally remote files/folder through an SSH connection.
• rclone - Mount cloud storage services like Dropbox, GDrive, Amazon S3 or Google Cloud Storage and open data locally.
• gocryptfs - Encrypted overlay system. Files are stored encrypted but once the FS is mounted they appear as plaintext in the mountpoint.
• kbfs - Distributed filesystem with end-to-end encryption. You can have private, shared and public folders.
• borgbackup - Mount your deduplicated, compressed and encrypted backups for ease of browsing.

Backups

https://www.cisa.gov/uscert/sites/default/files/publications/data_backup_options.pdf

Filesystem Hierarchy Standard

• /bin - Essential command binaries
• /sbin - Essential system binaries, usually to be run by root
• /dev - Device files, special files that often are interfaces to hardware devices
• /etc - Host-specific system-wide configuration files
• /home - Home directories for users in the system
• /lib - Common libraries for system programs
• /opt - Optional application software
• /sys - Contains information and configuration for the system
• /tmp - Temporary files (also /var/tmp). Usually deleted between reboots.
• /usr/ - Read only user data
  • /usr/bin - Non-essential command binaries
  • /usr/sbin - Non-essential system binaries, usually to be run by root
  • /usr/local/bin - Binaries for user compiled programs
• /var - Variable files like logs or caches