NAME

       sd_uid_get_state, sd_uid_is_on_seat, sd_uid_get_sessions, sd_uid_get_seats,
       sd_uid_get_display - 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);

       int sd_uid_get_display(uid_t uid, char **session);

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 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.

       Similarly, 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().

       sd_uid_get_display() returns the name of the "primary" session of a user. If the user has
       graphical sessions, it will be the oldest graphical session. Otherwise, it will be the
       oldest open session.

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.
       sd_uid_get_display() returns a non-negative code on success. On failure, these calls
       return a negative errno-style error code.

   Errors
       Returned errors may indicate the following problems:

       -ENODATA
           The given field is not specified for the described user.

       -ENXIO
           The specified seat is unknown.

       -EINVAL
           An input parameter was invalid (out of range, or NULL, where that is not accepted).
           This is also returned if the passed user ID is 0xFFFF or 0xFFFFFFFF, which are
           undefined on Linux.

       -ENOMEM
           Memory allocation failed.

NOTES

       These APIs are implemented as a shared library, which can be compiled and linked to with
       the libsystemd pkg-config(1) file.

SEE ALSO

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