sd_seat_get_active - Man Page

#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​.

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

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