sd_seat_get_active, sd_seat_get_sessions, sd_seat_can_tty, sd_seat_can_graphical — Determine state of a specific seat
#include <systemd/sd-login.h>
int sd_seat_get_active( | const char *seat, |
| char **session, | |
uid_t *uid); |
int sd_seat_get_sessions( | const char *seat, |
| char ***ret_sessions, | |
| uid_t **ret_uids, | |
unsigned int *ret_n_uids); |
int sd_seat_can_tty( | const char *seat); |
int sd_seat_can_graphical( | const char *seat); |
sd_seat_get_active() may be used to
determine which session is currently active on a seat, if there is
any. Returns the session identifier and the user identifier of the
Unix user the session is belonging to. Either the session or the
user identifier parameter can be passed NULL,
in case only one of the parameters shall be queried. The returned
string needs to be freed with the libc
free(3)
call after use.
sd_seat_get_sessions() may be used to determine all sessions on the specified
seat. Returns two arrays, one (NULL terminated) with the session identifiers of the
sessions and one with the user identifiers of the Unix users the sessions belong to. An additional
parameter may be used to return the number of entries in the latter array. This value is the same as the
return value if the return value is nonnegative. The output parameters may be passed as
NULL in case these output values are not needed. The arrays and the strings
referenced by them need to be freed with the libc free(3) call after
use. Note that instead of an empty array NULL may be returned and should be
considered equivalent to an empty array.
sd_seat_can_tty() may be used to
determine whether a specific seat provides TTY functionality, i.e.
is useful as a text console.
sd_seat_can_graphical() may be used to
determine whether a specific seat provides graphics functionality,
i.e. is useful as a graphics display.
If the seat parameter of any of these
functions is passed as NULL, the operation is
executed for the seat of the session of the calling process, if
there is any.
On success, sd_seat_get_active() returns 0 or a positive integer. On success,
sd_seat_get_sessions() returns the number of entries in the session identifier
array. If the test succeeds,
sd_seat_can_tty() and sd_seat_can_graphical() return a positive
integer, if it fails 0. On failure, these calls return a negative errno-style error code.
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.