SD_UID_GET_STATE(3) sd_uid_get_state SD_UID_GET_STATE(3)
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
int sd_uid_get_state(uid_t pid, char** state);
int sd_uid_is_on_seat(uid_t pid, int require_active, const char* seat);
int sd_uid_get_sessions(uid_t pid, int require_active, char*** sessions);
int sd_uid_get_seats(uid_t pid, int require_active, char*** seats);
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), active (user logged in on an active seat). 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. 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. Acceptes a Unix user identifier as parameter.
The require_active boolean parameter controls whether the returned list shall consist of only those sessions where the user is currently
active (true) or where the user is currently logged in at all, possibly inactive (false). 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().
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.
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-login pkg-config(1) file.
systemd(1), sd-login(7), sd_pid_get_owner_uid(3)
Lennart Poettering <firstname.lastname@example.org>
systemd 10/07/2013 SD_UID_GET_STATE(3)