Command-line Environment

• Job Control

  • Killing a process

    • Ctrl-C: deliver a SIGINT signal to the process.
    • use the SIGQUIT signal instead, by typing Ctrl-\
    • Note that ^ is how Ctrl is displayed when typed in the terminal.
    • a more generic signal for asking a process to exit gracefully is the SIGTERM signal
      • kill -TERM <PID>

  • Pausing and backgrounding processes

    • typing Ctrl-Z will prompt the shell to send a SIGTSTP signal

    • continue the paused job in the foreground or in the background using fg or bg

    • The jobs command lists the unfinished jobs associated with the current terminal session.

      • use pgrep to find that out

    • refer to the last backgrounded job you can use the $! special parameter

    • the & suffix in a command will run the command in the background

    • To background an already running program you can do Ctrl-Z followed by bg.

      • SIGHUP
      • nohup (a wrapper to ignore SIGHUP), or use disown if the process has already been started

    • other signals here or typing man signal or kill -l.

• Terminal Multiplexers

  Terminal multiplexers like tmux allow you to multiplex terminal windows using panes and tabs so you can interact with multiple shell sessions.

  • keybindings: the form <C-b> x where that means (1) press Ctrl+b, (2) release Ctrl+b, and then (3) press x.
  • hierarchy of objects:
    • Sessions - an independent workspace with one or more windows
      • tmux starts a new session.
      • tmux new -s NAME starts it with that name.
      • tmux ls lists the current sessions
      • Within tmux typing <C-b> d detaches the current session
      • tmux a attaches the last session. You can use -t flag to specify which
    • Windows - tabs in editors or browsers, they are visually separate parts of the same session
      • <C-b> c Creates a new window. To close it you can just terminate the shells doing <C-d>
      • <C-b> N Go to the N th window. Note they are numbered
      • <C-b> p Goes to the previous window
      • <C-b> n Goes to the next window
      • <C-b> , Rename the current window
      • <C-b> w List current windows
    • Panes - Like vim splits, panes let you have multiple shells in the same visual display.
      • <C-b> " Split the current pane horizontally
      • <C-b> % Split the current pane vertically
      • <C-b> <direction> Move to the pane in the specified direction. Direction here means arrow keys.
      • <C-b> z Toggle zoom for the current pane
      • <C-b> [ Start scrollback. You can then press <space> to start a selection and <enter> to copy that selection.
      • <C-b> <space> Cycle through pane arrangements.
  • here is a quick tutorial on tmux and this has a more detailed explanation that covers the original screen command.

• Aliases

  • Aliases have many convenient features:

  • # Make shorthands for common flags
    alias ll="ls -lh"
    
    # Save a lot of typing for common commands
    alias gs="git status"
    alias gc="git commit"
    alias v="vim"
    
    # Save you from mistyping
    alias sl=ls
    
    # Overwrite existing commands for better defaults
    alias mv="mv -i"           # -i prompts before overwrite
    alias mkdir="mkdir -p"     # -p make parent dirs as needed
    alias df="df -h"           # -h prints human readable format
    
    # Alias can be composed
    alias la="ls -A"
    alias lla="la -l"
    
    # To ignore an alias run it prepended with \
    \ls
    # Or disable an alias altogether with unalias
    unalias la
    
    # To get an alias definition just call it with alias
    alias ll
    # Will print ll='ls -lh'
    

  • include it in shell startup files, like .bashrc or .zshrc,

• Dotfiles

  • For bash, editing your .bashrc or .bash_profile will work in most systems.

    • PATH environment, like export PATH="$PATH:/path/to/program/bin"

  • git - ~/.gitconfig

  • vim - ~/.vimrc and the ~/.vim folder

  • ssh - ~/.ssh/config

  • tmux - ~/.tmux.conf

  • in their own folder, under version control, and symlinked into place using a script

  • Portability

• Remote Machines

  • SSH is highly configurable so it is worth learning about it.

  • SSH Keys: ~/.ssh/id_rsa

    • Key generation: run ssh-keygen.

      • ssh-keygen -o -a 100 -t ed25519 -f ~/.ssh/id_ed25519
        

    • Key based authentication

      • ssh will look into .ssh/authorized_keys to determine which clients it should let in
      • ssh-copy-id

  • Copying files over SSH

    • ssh+tee
    • scp when copying large amounts of files/directories
    • rsync improves upon scp by detecting identical files in local and remote, and preventing copying them again.

  • Port Forwarding

    • SSH Configuration

    • alias my_server="ssh -i ~/.id_ed25519 --port 2222 -L 9999:localhost:8888 foobar@remote_server
      

      • a better alternative using ~/.ssh/config.
      • be thoughtful about sharing your SSH configuration.

• Shells & Frameworks

  • bash, zsh/ fish/
  • general frameworks are prezto or oh-my-zsh
  • zsh-syntax-highlighting or zsh-history-substring-search
  • One thing to note when using these frameworks is that they may slow down your shell

• Terminal Emulators

  • Font choice
  • Color Scheme
  • Keyboard shortcuts
  • Tab/Pane support
  • Scrollback configuration
  • Performance (some newer terminals like Alacritty or kitty offer GPU acceleration).