prehook

A prehook is a mechanism in software systems that runs before a specified operation to prepare, validate, or modify the upcoming action. It serves as a gatekeeper or preparatory step, allowing code to inspect inputs, ensure prerequisites, or apply changes before the main operation proceeds. The term is descriptive rather than standardized, and different tools may implement similar functionality under different names or with varying interfaces.

In version control, the concept is most commonly seen with pre-operation hooks. For example, a pre-commit hook in Git runs before a new commit is created. It can run checks such as linters, unit tests, or formatting validations, and may abort the commit by returning a nonzero exit status if conditions are not met. This helps enforce quality gates before changes enter the repository history.

Beyond version control, prehooks appear in package managers, build systems, and deployment pipelines. Systems may define preinstall or prepublish scripts (for example in npm) that run before the corresponding lifecycle step, ensuring the environment is correct or that prerequisites are satisfied. In continuous integration and deployment, prehooks can verify credentials, configuration, or dependencies before proceeding with builds or releases.

Implementation typically involves callbacks or scripts registered for a specific event. Prehooks can be synchronous or asynchronous and should be designed to be deterministic and, when possible, idempotent. They may modify inputs or environment, or simply abort the operation to prevent unintended outcomes. See also: hooks, pre- and post- operation processes.