|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | HISTORY | SEE ALSO | COLOPHON |
|
|
|
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, sd_uid_get_display, sd_uid_get_login_time -
Determine login state of a specific Unix user ID
#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);
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.
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.
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.
sd_uid_get_display() was added in version 213.
sd_uid_get_login_time() was added in version 254.
systemd(1), sd-login(3), sd_pid_get_owner_uid(3)
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
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover 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 to
man-pages@man7.org
systemd 258~rc2 SD_UID_GET_STATE(3)
Pages that refer to this page: sd-login(3), org.freedesktop.login1(5), systemd.directives(7), systemd.index(7)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|