/ziː ʃɛl/ or /zɛd ʃɛl/
n. "Extended UNIX shell blending Bourne compatibility with interactive superpowers like spelling correction and recursive globbing."
zsh, short for Z shell, extends the Bourne shell family as a highly customizable command-line interpreter for interactive use and scripting, featuring programmable tab completion, shared history across sessions, extended globbing, and themeable prompts via plugins like Oh My Zsh. Unlike bash's simpler autocomplete, zsh predicts commands/paths/options contextually (e.g., git st → git status), corrects typos automatically, and supports **/*.py recursive matching natively—making it macOS default since Catalina while powering frameworks like prezto and Oh My Zsh (200K+ GitHub stars).
Key characteristics of zsh include: Programmable Completion predicts full commands/flags/files from context (hundreds builtin, extensible via compinit); Shared History synchronizes ~/.zsh_history across tabs/sessions unlike bash's per-shell isolation; Extended Globbing with **/ recursion, (*.jpg|*.png) alternation, and qualifiers like **.py~test.py (exclude); Spelling Correction auto-fixes sl → ls with % confirmation; Themeable Prompts via prompt themes or Powerlevel10k (git status, execution time).
Conceptual example of zsh usage:
# Install Oh My Zsh + switch default shell
sh -c "$(curl -fsSL https://raw.github.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"
chsh -s /bin/zsh
# .zshrc excerpt with plugins
plugins=(git zsh-autosuggestions zsh-syntax-highlighting)
source $ZSH/oh-my-zsh.sh
# zsh globbing magic
ls **/*.py # recursive Python files
ls *.(jpg|png) # image files only
rm **/*~(*.md|README) # delete everything except markdown
Conceptually, zsh transforms the terminal from cryptic command prompter into intelligent assistant—anticipating keystrokes, healing typos, and globbing filesystems like regex wizardry, contrasting bash's raw POSIX simplicity. Pairs perfectly with tmux/nvim for dev workflows, where Oh My Zsh plugins (pip-like zplug) extend syntax highlighting/autosuggestions, though startup slightly slower than bash without optimizations. Master via zsh -x tracing or man zshoptions for 200+ toggles.