for APT2

Primary API (most commonly used)
AptCache — Access to the package cache.
AptPolicy — Package pinning.
AptSession — Easy high-level API for APT2 programs.
AptSystem — Dynamically loaded modules for system-specific parts.
Secondary API (parsers, utility functions)
AptConfiguration — Reading APT configuration files.
AptControlFile — Parsing files consisting of multiple RFC-822 sections.
AptSourcesList — Parse sources.list files and create AptSource objects.
Utility Functions — Various utility functions that do not fit elsewhere.
Internal API
Cache Format — Specification of the APT2 cache format
Cache Builder — Building caches
API Index

The Advanced Package Tool Library is a library to create package management solutions for UNIX-like systems. This reference manual explains the API and shows how to use it.