Terminal Cheatsheet

── The model ────────────────────────────
terminal emulator: draws text, sends keystrokes
shell (bash/zsh): parses commands, runs programs
they're separate programs — either swaps out

pressing Enter:
  1. shell expands:  $VARS  *.glob  ~  $(cmd)
  2. finds program:  aliases -> builtins -> $PATH dirs
  3. fork + exec, wires up the 3 streams
  4. waits; exit code lands in $?

streams: 0=stdin 1=stdout 2=stderr
  cmd > f        stdout to file
  cmd 2> f       stderr to file
  cmd > f 2>&1   both
  cmd1 | cmd2    stdout -> next stdin
  cmd && next    only on success
environment: KEY=value copied parent -> child
  export makes a var inheritable; never flows back
startup files: ~/.bashrc / ~/.zshrc (PATH, aliases)
escape codes: ESC[32m = green; cursor moves; \r redraw
  vim/htop = raw mode + furious redrawing

# ── Keystrokes that matter ──────────────
# Ctrl+C  kill current program (SIGINT)
# Ctrl+Z  suspend (fg to resume, bg to background)
# Ctrl+D  end of input / close shell
# Ctrl+R  search command history
# Ctrl+A/E  start/end of line   Ctrl+W  delete word
# Tab     complete   Tab Tab  show options
# !!      last command    !$   its last argument

# ── Diagnosis one-liners ────────────────
type CMD               # alias? builtin? which file?
echo $PATH             # where commands are searched
echo $?                # did the last command succeed?
env | sort             # my environment
history | tail -20
stty sane              # fix a garbled terminal (+ Enter)

# ── Jobs ────────────────────────────────
long_task &            # start in background
jobs                   # list them
fg %1; bg %1           # foreground / background
nohup task &           # survives closing the terminal

# ── SSH & remote ────────────────────────
ssh user@host                  # remote shell
ssh-keygen -t ed25519          # make keys (once)
ssh-copy-id user@host          # passwordless login
ssh user@host 'df -h'          # one remote command
scp file user@host:/path/      # copy over ssh
rsync -av src/ user@host:dst/  # sync, resumable
tmux                           # persistent session
# Ctrl+B D to detach; tmux attach to resume