🧭 The Lineage — Which shell came first?
🕰️ 1. Thompson Shell (sh) — 1971
- The original shell for Version 1 UNIX.
- Very limited scripting.
🕰️ 2. Bourne Shell (sh) — 1979
- Developed by Stephen Bourne at Bell Labs for UNIX Version 7.
- Became the standard UNIX shell.
- Introduced proper scripting capabilities (if, for, case, etc.)
- This is what most POSIX-compatible shells are based on.
🧱 From Bourne Shell came…
| Shell | Year | Why it exists |
|---|---|---|
| Bash (Bourne Again Shell) | 1989 | GNU’s free/open alternative to Bourne shell; adds features like history, job control |
| KornShell (ksh) | 1980s | Combines sh and csh features, used in commercial UNIX |
| Zsh | Early 1990s | Powerful scripting + interactive features; loved by power users |
| Dash | Modern | Lightweight, fast — often used for scripts on Ubuntu for speed (replaces /bin/sh) |
| Fish | 2005 | ”Friendly Interactive SHell” — focused on user-friendliness, not POSIX scripting |
🔁 Why do multiple shells still exist?
Because each has tradeoffs:
| Shell | Best for |
|---|---|
bash | Default for most Linux distros; good balance |
zsh | Interactive users who want themes, plugins (with Oh My Zsh) |
sh/dash | Running simple, portable scripts |
fish | Beginners who want autocompletion & modern UX |
ksh | Legacy commercial UNIX systems (e.g., AIX, Solaris) |