apt - Advanced Package Tool
APT is a management system for software packages. It is still under development; the snazzy front ends are not yet available. In the meantime, please see apt-get(8).
apt returns zero on normal operation, decimal 100 on error.
This manpage isn't even started.
See the APT bug page, /usr/share/doc/debian/bug-reporting.txt or the bug(1)? command.