Things you didn't know about GNU readline (2019)

Original Article ↗ Hacker News Discussion ↗

Readline usage and configuration

  • Many commenters only recently realized how configurable Readline is and express enthusiasm about customizing it system‑wide.
  • Common keybindings praised: history search (Ctrl‑r/Ctrl‑s), line killing (Ctrl‑u, Ctrl‑k), yanking (Ctrl‑y, Esc‑y), and last‑argument recall (Alt+.).
  • Several advise against rebinding core keys like Ctrl‑k, arguing that standard bindings transfer across many tools and machines.
  • Users share .inputrc tricks: showing current mode in the prompt, changing cursor shape per mode, and vi/emacs mode strings.

Vi vs Emacs modes and ergonomics

  • Vim users are often disappointed by set -o vi in shells; they prefer Readline/Emacs-style bindings in most places and Vim only in the editor.
  • Others say vi mode becomes usable if the prompt indicates mode and cursor shape changes.
  • There is light debate over whether Emacs-style keybindings contribute to RSI; anecdotes support both “no evidence” and “Vim helped my RSI”.

GPLv3 licensing concerns

  • Several participants worry that Readline’s GPLv3 license prevents its use in proprietary or embedded products and can “sneak in” via dependencies.
  • Others counter that this mainly matters for distributed, especially proprietary, software, not internal tools.
  • There is disagreement about whether giving GPL‑using binaries to contractors counts as distribution; some cite FSF guidance that it does.
  • Some companies reportedly ban GPLv3 code entirely; others happily ship GPLv3 and see it as enabling use of more libraries.

Alternatives and wrappers

  • rlwrap and socat readline are highlighted as ways to add Readline‑like editing and history to programs lacking it (e.g., sqlplus, Prolog REPLs, ed).
  • Non‑GPL alternatives such as libedit/tecla are mentioned; some shells (dash, busybox ash) can use libedit or provide partial Readline‑like features.
  • Windows tools like Clink and BusyBox ports are recommended for gaining a modern, Readline‑style shell experience.

Quality-of-life, bugs, and maintenance

  • Users describe how painful non‑Readline CLIs (old Oracle tools, psql --no-readline, early MS‑DOS) highlight how much Readline improves UX.
  • One commenter reports helping diagnose and fix an O(n²) performance bug in Readline when pasting long inputs.
  • There is concern that critical tools like Readline are maintained by very few unpaid individuals, raising sustainability and security worries, with calls for better funding.