xsh

xsh is a fast and modular POSIX-like Unix shell written in modern C (C23 standard).

Building

Requirements

• C23 conforming compiler (gcc 14+ or clang 18+)
• Meson build system (1.3.0+)
• Ninja build tool
• GNU Readline
• GNU gettext (for translations)

Compilation

meson setup build
ninja -C build

Testing

meson test -C build --verbose

Installation

ninja -C build install

Documentation

• User Manual
• Man Page
• Example Configuration

Configuration

xsh loads configuration from ~/.xshrc upon startup.

Build-time options can be configured via meson configure:

meson setup build -Ddefault_histsize=2000 -Ddefault_completion_drivers="native,fish,bash,zsh"

Architecture

xsh is structured into modular components:

• Lexer: Tokenizer with streaming support, line continuation checks, and quoting awareness.
• Parser: Recursive-descent parser producing an Abstract Syntax Tree (AST) supporting pipes, logical operators, redirection chains, subshells, command groups, if/elif/else branching, while/until/for loops, case pattern matching, and function definitions.
• Line Editor: Readline integration with prompt formatting, multiline inputs, and completion hook dispatching.
• Completion Engine: Pluggable framework with native xsh completions, fish completions, bash completions, and zsh completions.
• Job Control: Process group management, foreground/background pipeline handling, and job status notifications.
• Builtins: Core POSIX and interactive utilities.
• Variables and Expansions: Parameter expansion, command substitution, arithmetic expansion, and wildcard pathname expansion.

Roadmap

• Basic command execution and argument parsing
• Input and output redirections (<, >, >>, 2>, 2>>, &>, &>>, 2>&1, 1>&2, <<)
• Pipeline execution (|)
• Logical chaining (&&, ||, ;, &)
• Subshells and command grouping ((...), { ...; })
• Conditional execution (if, then, elif, else, fi)
• Loops (while, until, for)
• Functions and local scope
• Arithmetic expansion ($((...)))
• Command substitution ($(...), `...`)
• Process substitution (<(...), >(...))
• Brace expansion ({a,b,c}, {1..10}, {01..05}, {a..z..2})
• ANSI-C quoting ($'...')
• Indexed arrays (arr=(...), ${arr[i]}, ${arr[@]}, ${arr[*]}, ${#arr[@]}, ${!arr[@]})
• Parameter expansion ($VAR, ${VAR})
• Wildcard pattern matching (globbing)
• Signal handling and job control (jobs, fg, bg, disown)
• Core builtins (cd, pwd, echo, printf, times, export, unset, exit, test, [, [[, break, continue, return, history, bind, source, ., builtins, help)
• Interactive line editing with GNU Readline
• History persistence and limit controls
• Configurable prompt strings (PS1)
• Command line hooks (precmd, chpwd, PROMPT_COMMAND)
• Modular completion architecture
  • Native xsh completion format (complete builtin)
  • Fish completion format support
  • Bash completion format support
  • Zsh completion format support
  • Configurable completion drivers and fallback paths in ~/.xshrc
• POSIX Compatibility
  • Pattern matching and branching (case ... in ... esac)
  • Parameter expansions (${#var}, ${var#pattern}, ${var##pattern}, ${var%pattern}, ${var%%pattern}, ${var:=default}, ${var:+alt}, ${var:?err})
  • Process and signal control (trap, kill, wait, exec, eval)
  • Input and parameter builtins (read, shift, getopts, umask, printf, times)
  • Shell introspection and modes (type, command, alias, unalias, set -e, set -u, set -x, set -f)
  • Resource limits builtin (ulimit)
• Automated test suite (meson test)
  • Basic commands, pipelines, and grouping tests
  • Redirections and heredocs tests
  • Control structures and pattern matching tests
  • Arithmetic, parameter, and string expansions tests
  • Brace expansion tests
  • ANSI-C quoting tests
  • Indexed arrays tests
  • Shell functions, scoping, and recursion tests
  • POSIX utilities, options, aliases, and types tests
  • Process resource limits tests
  • Command line hooks tests
  • Localization and translation tests
• Project documentation and manual
  • UNIX manual page (doc/xsh.1)
  • User manual guide (doc/manual.md)
  • Example configuration (examples/xshrc)
• Internationalization and localization (i18n / l10n)
  • GNU gettext integration via Meson
  • Russian translation catalog (po/ru.po)

License

GNU General Public License v3.0