ast-grep is a powerful CLI tool that lets you search and modify code based on its structure rather than text patterns. Using abstract syntax tree matching, it works like grep but understands code syntax, allowing you to write patterns that look like ordinary code and match all structurally identical code regardless of formatting.

Key capabilities include:

Structural pattern matching - Write patterns as normal code with $VARIABLE wildcards to match any AST node
Multi-language support - Reuse the same patterns across JavaScript, TypeScript, Python, Java, Go, Rust and more
Bulk refactoring - Use the --rewrite flag to automatically transform matching code at scale
Interactive mode - Review and approve changes before applying them
YAML-based linting - Define custom lint rules in configuration files without coding
Project organization - Centralize rules in project configs and share across teams
CI integration - Plug into GitHub Actions to enforce patterns automatically
JSON export - Pipe matches to jq or other tools for custom processing
Performance - Built in Rust with tree-sitter parsing and multi-core support

Perfect for library authors migrating APIs, tech leads enforcing code standards, security researchers writing detection rules, or anyone automating repetitive code changes across large repositories.

Pip