Two sets of application programming interfaces (API) enable user accounting data to be accessed by applications. The preferred set of programming interfaces for accessing and manipulating user accounting information is described on the getutxent(3C) man page. These interfaces are more capable and more portable than the older getutent(3C) routines.
Older applications can access the underlying accounting files directly. The files /var/adm/utmp and /var/adm/wtmp and the corresponding symbolic links /etc/utmp and /etc/wtmp are no longer supported. The format of the data that is contained in these files constrains the future evolution of the Solaris operating environment. Applications that use these files should be updated to use the documented and supported APIs.
Applications that are already using the getutent(3C) family of routines might be unaffected on small system configurations. However, in future releases these interfaces might return errors when you use them on very large system configurations. For this reason, use the getutxent(3C) routines for old code and new code instead of the getutent(3C) APIs.