UTMPX(5) File Formats Manual UTMPX(5)

utmpxuser accounting database

#include <utmpx.h>

In contrast to utmp and wtmp, the extended databases in utmpx and wtmpx reserve more space for logging hostnames, and also information on a process' ID, termination signal and exit status.

The ⟨utmpx.h⟩ header defines the structures and functions for logging user. Currently logged in users are tracked in /var/run/utmpx. The interface to the utmpx file is described in endutxent(3). The file is not automatically created if they do not exist; it must be created manually.

Traditionally, separate files would be used to store the running log of the logins and logouts (wtmpx), and the last login of each user (lastlogx). With the availability of the Apple system log facility asl(3), these separate files can be replace with log entries, which are automatically generated when utmpx entries are written. The API to access the logins and logouts is described in endutxent_wtmp(3) while the last login info is accessible with getlastlogx(3).

For compatibility, changes to utmpx are reflected in utmp(3) (in the utmp, wtmp and lastlog files), but not the other way around.

/var/run/utmpx
The utmpx file.

asl(3), endutxent(3), endutxent_wtmp(3), getlastlogx(3), utmp(5)

January 31, 2007 macOS 14.4