sd_get_seats, sd_get_sessions, sd_get_uids, sd_get_machine_names — Determine available seats, sessions, logged in users and virtual machines/containers
#include <systemd/sd-login.h>
int sd_get_seats( | char ***seats); |
int sd_get_sessions( | char ***sessions); |
int sd_get_uids( | uid_t **users); |
int sd_get_machine_names( | char ***machines); |
sd_get_seats() may be used to determine
all currently available local seats. Returns the number of seat
identifiers and if the input pointer is non-NULL, a
NULL-terminated array of seat identifiers
is stored at the address.
The returned array and all strings it references 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.
Similarly, sd_get_sessions() may be
used to determine all current login sessions.
Similarly, sd_get_uids() may be used to
determine all Unix users who currently have login sessions.
Similarly, sd_get_machine_names() may
be used to determine all current virtual machines and containers
on the system.
Note that the returned lists are not sorted and in an undefined order.
On success, sd_get_seats(), sd_get_sessions(),
sd_get_uids() and sd_get_machine_names() return the number of
entries in the arrays. 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.