16.3. User Accounting Databases

The Filesystem Hierarchy Standard specifies two optional locations for user accounting databases used by the getutent(), getutent_r(), getutxent(), getutxid(), getutxline(), and pututxline() functions. These are /var/run/utmp and /var/run/wtmp.

The LSB does not specify the format or structure of these files, or even if they are files at all. They should be used only as "magic cookies" to the utmpname() function.