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);
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.
Note that sd_id128_get_boot() always returns a UUID v4 compatible ID. 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() and sd_id128_get_boot() interfaces are available as a shared library, which can be compiled and linked to with the "libsystemd" pkg-config(1) file.