sd_seat_get_active

systemd

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

Description

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.

Return Value

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.

Errors

Returned errors may indicate the following problems:

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

-ENXIO
The specified seat is unknown.

-EINVAL
An input parameter was invalid (out of range, or NULL, where that is not accepted).

-ENOMEM
Memory allocation failed.

History

sd_seat_can_tty() and sd_seat_can_graphical() were added in version 186.