sd-login.h provides APIs to introspect and monitor seat, login
session and user status information on the local system.
See Multi-Seat on Linux for an introduction into multi-seat
support on Linux, the background for this set of APIs.
Note that these APIs only allow purely passive access and monitoring
of seats, sessions and users. To actively make changes to the seat
configuration, terminate login sessions, or switch session on a seat
you need to utilize the D-Bus API of systemd-logind, instead.
These functions synchronously access data in /proc, /sys/fs/cgroup
and /run. All of these are virtual file systems, hence the runtime
cost of the accesses is relatively cheap.
It is possible (and often a very good choice) to mix calls to the
synchronous interface of sd-login.h with the asynchronous D-Bus
interface of systemd-logind. However, if this is done you need to
think a bit about possible races since the stream of events from
D-Bus and from sd-login.h interfaces such as the login monitor are
asynchronous and not ordered against each other.
If the functions return string arrays, these are generally NULL
terminated and need to be freed by the caller with the libc free(3)
call after use, including the strings referenced therein. Similarly,
individual strings returned need to be freed, as well.
As a special exception, instead of an empty string array NULL may be
returned, which should be treated equivalent to an empty string
See sd_pid_get_session(3), sd_uid_get_state(3),
sd_session_is_active(3), sd_seat_get_active(3), sd_get_seats(3),
sd_login_monitor_new(3) for more information about the functions
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2017-03-13. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
systemd 233 SD-LOGIN(3)