sd_id128_get_machine, sd_id128_get_boot, sd_id128_get_invocation — Retrieve 128-bit IDs
#include <systemd/sd-id128.h>
int sd_id128_get_machine( | sd_id128_t *ret) ; |
int sd_id128_get_boot( | sd_id128_t *ret) ; |
int sd_id128_get_invocation( | sd_id128_t *ret) ; |
sd_id128_get_machine()
returns the
machine ID of the executing host. This reads and parses the
machine-id(5)
file. This function caches the machine ID internally to make
retrieving the machine ID a cheap operation.
sd_id128_get_boot()
returns the boot ID
of the executing kernel. This reads and parses the
/proc/sys/kernel/random/boot_id
file exposed
by the kernel. It is randomly generated early at boot and is
unique for every running kernel instance. See
random(4)
for more information. This function also internally caches the
returned ID to make this call a cheap operation.
sd_id128_get_invocation()
returns the invocation ID of the currently executed
service. In its current implementation, this reads and parses the $INVOCATION_ID
environment
variable that the service manager sets when activating a service, see
systemd.exec(5) for details. The
ID is cached internally. In future a different mechanism to determine the invocation ID may be added.
Note that sd_id128_get_boot()
and sd_id128_get_invocation()
always
return UUID v4 compatible IDs. sd_id128_get_machine()
will also return a UUID v4-compatible
ID on new installations but might not on older. It is possible to convert the machine ID into a UUID v4-compatible
one. For more information, see
machine-id(5).
For more information about the "sd_id128_t
"
type see
sd-id128(3).
The two calls return 0 on success (in which case
ret
is filled in), or a negative
errno-style error code.
The sd_id128_get_machine()
, sd_id128_get_boot()
and
sd_id128_get_invocation()
interfaces are available as a shared library, which can be compiled
and linked to with the "libsystemd
" pkg-config(1) file.