Using custom queries with the CodeQL CLI

You can customize your CodeQL analyses by writing your own queries to highlight specific vulnerabilities or errors.

This topic is specifically about writing queries to use with the database analyze command to produce interpreted results.

Other query-running commands

Queries run with database analyze have strict metadata requirements. You can also execute queries using the following plumbing-level subcommands:

  • database run-queries, which outputs non-interpreted results in an intermediate binary format called BQRS.
  • query run, which will output BQRS files, or print results tables directly to the command line. Viewing results directly in the command line may be useful for iterative query development using the CLI.

Queries run with these commands don’t have the same metadata requirements. However, to save human-readable data you have to process each BQRS results file using the bqrs decode plumbing subcommand. Therefore, for most use cases it’s easiest to use database analyze to directly generate interpreted results.

Writing a valid query

Before running a custom analysis you need to write a valid query, and save it in a file with a .ql extension. There is extensive documentation available to help you write queries. For more information, see “CodeQL queries” in the “Learning CodeQL help.”

Including query metadata

Query metadata is included at the top of each query file. It provides users with information about the query, and tells the CodeQL CLI how to process the query results.

When running queries with the database analyze command, you must include the following two properties to ensure that the results are interpreted correctly:

  • Query identifier (@id): a sequence of words composed of lowercase letters or digits, delimited by / or -, identifying and classifying the query.
  • Query type (@kind): identifies the query is an alert (@kind problem) or a path (@kind path-problem).

For more information about these metadata properties, see “Metadata for CodeQL queries” and the Query metadata style guide.

Note

Metadata requirements may differ if you want to use your query with other applications. For more information, see About CodeQL queries in the “Learning CodeQL help.”

Creating a custom QL pack

When writing your own queries, you should save them in a custom QL pack directory. QL packs provide a way of organizing the files used in CodeQL analysis. This directory must contain a file named qlpack.yml at the root. Your custom queries should be saved in the QL pack root, or its subdirectories.

For each QL pack, the qlpack.yml file includes information that tells CodeQL how to compile the queries, what libraries the pack depends on, and where to find query suite definitions. For more information about what to include in this file, see “About QL packs.”

Contributing to the CodeQL repository

If you would like to share your query with other CodeQL users, you can open a pull request in the CodeQL repository. For further information, see Contributing to CodeQL.

Further reading