lastlog is a program available on most Linux distributions. It formats and prints the contents of the last login log file, <code>/var/log/lastlog</code> (which is a usually a very sparse file), including the login name, port, and last login date and time. It is similar in functionality to the BSD program last, also included in Linux distributions; however, last parses a different binary database file (<code>/var/log/wtmp</code> and <code>/var/log/btmp</code>).
The file is updated by the <code>pam_lastlog.so</code> Pluggable Authentication Module. The module has been deprecated since 2023, and is announced to be removed in future releases of the pam-linux framework, due to the data structures inherently being affected by the Year 2038 problem.
Lastlog prints its output in column format with login-name, port, and last-login-time of each and every user on the system mentioned in that order. The users are sorted by default according to the order in <code>/etc/passwd</code> However, it can also be used to modify the records kept in <code>/var/log/lastlog</code>.