Ubuntu Manpage: sd_uid_get_state, sd_uid_is_on_seat, sd_uid_get_sessions, sd_uid_get

Provided by: libsystemd-dev_256.5-2ubuntu3.1_amd64

NAME

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

       int sd_uid_get_login_time(uid_t uid, uint64_t *usec);

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.

sd_uid_get_login_time() may be used to determine the time the user's service manager has
been invoked, which is the time when the user's first active session, since which they
stayed logged in continuously, began. The usec is in microseconds since the epoch
(CLOCK_REALTIME). This call will fail with -ENXIO if the user is not currently logged in.

RETURN VALUE

       On success, sd_uid_get_state() and sd_uid_get_login_time() 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

       Functions described here are available as a shared library, which can be compiled against
       and linked to with the libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be not multi-thread-safe.
       This means that the code calling the functions described here must not call setenv(3) from
       a parallel thread. It is recommended to only do calls to setenv() from an early phase of
       the program when no other threads have been started.

HISTORY