NAME

       sd_uid_get_state, sd_uid_is_on_seat, sd_uid_get_sessions, sd_uid_get_seats - Determine
       login state of a specific Unix user ID

SYNOPSIS

       #include <systemd/sd-login.h>

       int sd_uid_get_state(uid_t uid, char** state);

       int sd_uid_is_on_seat(uid_t uid, int require_active, const char* seat);

       int sd_uid_get_sessions(uid_t uid, int require_active, char*** sessions);

       int sd_uid_get_seats(uid_t uid, int require_active, char*** seats);

DESCRIPTION

       sd_uid_get_state() may be used to determine the login state of a specific Unix user
       identifier. The following states are currently known: offline (user not logged in at all),
       lingering (user not logged in, but some user services running), online (user logged in,
       but not active, i.e. has no session in the foreground), active (user logged in, and has at
       least one active session, i.e. one session in the foreground), closing (user not logged
       in, and not lingering, but some processes are still around). In the future additional
       states might be defined, client code should be written to be robust in regards to
       additional state strings being returned. The returned string needs to be freed with the
       libc free(3) call after use.

       sd_uid_is_on_seat() may be used to determine whether a specific user is logged in or
       active on a specific seat. Accepts a Unix user identifier and a seat identifier string as
       parameters. The require_active parameter is a boolean value. If non-zero (true) this
       function will test if the user is active (i.e. has a session that is in the foreground and
       accepting user input) on the specified seat, otherwise (false) only if the user is logged
       in (and possibly inactive) on the specified seat.

       sd_uid_get_sessions() may be used to determine the current sessions of the specified user.
       Accepts a Unix user identifier as parameter. The require_active parameter controls whether
       the returned list shall consist of only those sessions where the user is currently active
       (> 0), where the user is currently online but possibly inactive (= 0), or logged in at all
       but possibly closing the session (< 0). The call returns a NULL terminated string array of
       session identifiers in sessions which needs to be freed by the caller with the libc
       free(3) call after use, including all the strings referenced. If the string array
       parameter is passed as NULL the array will not be filled in, but the return code still
       indicates the number of current sessions. Note that instead of an empty array NULL may be
       returned and should be considered equivalent to an empty array.

       Similar, sd_uid_get_seats() may be used to determine the list of seats on which the user
       currently has sessions. Similar semantics apply, however note that the user may have
       multiple sessions on the same seat as well as sessions with no attached seat and hence the
       number of entries in the returned array may differ from the one returned by
       sd_uid_get_sessions().

RETURN VALUE

       On success sd_uid_get_state() returns 0 or a positive integer. If the test succeeds
       sd_uid_is_on_seat() returns a positive integer, if it fails 0.  sd_uid_get_sessions() and
       sd_uid_get_seats() return the number of entries in the returned arrays. On failure, these
       calls return a negative errno-style error code.

NOTES

       The sd_uid_get_state(), sd_uid_is_on_seat(), sd_uid_get_sessions(), and sd_uid_get_seats()
       interfaces are available as shared library, which can be compiled and linked to with the
       libsystemd-loginpkg-config(1) file.

SEE ALSO

       systemd(1), sd-login(3), sd_pid_get_owner_uid(3)