nsh

Nsh is the name of several small, lightweight Unix-like shells. There is no single canonical nsh; different projects have independently used the name for their minimal command interpreters.

Origins and distribution: The best-known nsh implementations appeared in academic or hobbyist contexts during the late 1990s and early 2000s, often as teaching tools or components of small embedded systems. Some versions were included in minimal operating systems used in education or embedded devices.

Design and features: Typical nsh shells aim for small size and straightforward behavior. They provide a command-line interface, basic job control in some variants, command execution, redirection, pipes, simple scripting constructs, and variable substitution. They are usually written in C and emphasize portability and small memory usage. Some implementations offer minimal readline support for line editing, and can be used as an alternative to more feature-rich shells in constrained environments.

Usage and legacy: Because nsh refers to several independent projects, capabilities vary widely. In practice, nsh shells are used in teaching OS concepts, in embedded environments, or as part of experiments in shell design. They are generally not intended as a drop-in replacement for mainstream shells like sh, dash, bash, or zsh, which are more feature-rich and actively maintained.

See also: sh, dash, ash, busybox ash, plan 9 rc. Notes: The article intentionally keeps to general characteristics due to multiple unrelated projects sharing the name.