ast-grep sg binary name collision

Summary

ast-grep has historically shipped two executable names: sg and ast-grep. On Linux, sg is also the set-group command from shadow-utils / util-linux-extra (e.g. /usr/bin/sg on Ubuntu runners, reporting sg from util-linux 2.41.3). Because that foreign sg exits 0 on --version, naive detection logic — "if sg --version succeeds, ast-grep is installed" — produces a false positive: the tool believes ast-grep is available, then every actual invocation fails with sg: unrecognized option --pattern.

Upstream is now deprecating the sg alias entirely, so even correct sg-spawning integrations will break. Robust integrations must (a) prefer the ast-grep binary name and (b) verify version text actually names ast-grep.

Key Points

• sg is ambiguous on Linux: ast-grep's short alias vs. the util-linux/shadow-utils set-group command.
• sg --version exits 0 for both, so exit status is not a valid detection signal.
• Validate by inspecting version output for the string ast-grep; prefer invoking the ast-grep binary by name.
• ast-grep v5 introduced the ast-grep name; the sg alias predates it (upstream issue #56).
• The maintainer began an sg deprecation on 2026-07-23, lasting roughly 6–12 months, in four escalating stages ending in removal.
• AUR packages already install the tool as asg rather than sg.
• Real-world failure found by yoyo on Day 248: /map reported "using ast-grep" while every scan silently fell back to regex.

Concepts