'\" t
.TH "SD_ID128_GET_MACHINE" "3" "" "systemd 232" "sd_id128_get_machine"
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.SH "NAME"
sd_id128_get_machine, sd_id128_get_boot, sd_id128_get_invocation \- Retrieve 128\-bit IDs
.SH "SYNOPSIS"
.sp
.ft B
.nf
#include <systemd/sd\-id128\&.h>
.fi
.ft
.HP \w'int\ sd_id128_get_machine('u
.BI "int sd_id128_get_machine(sd_id128_t\ *" "ret" ");"
.HP \w'int\ sd_id128_get_boot('u
.BI "int sd_id128_get_boot(sd_id128_t\ *" "ret" ");"
.HP \w'int\ sd_id128_get_invocation('u
.BI "int sd_id128_get_invocation(sd_id128_t\ *" "ret" ");"
.SH "DESCRIPTION"
.PP
\fBsd_id128_get_machine()\fR
returns the machine ID of the executing host\&. This reads and parses the
\fBmachine-id\fR(5)
file\&. This function caches the machine ID internally to make retrieving the machine ID a cheap operation\&.
.PP
\fBsd_id128_get_boot()\fR
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
\fBrandom\fR(4)
for more information\&. This function also internally caches the returned ID to make this call a cheap operation\&.
.PP
\fBsd_id128_get_invocation()\fR
returns the invocation ID of the currently executed service\&. In its current implementation, this reads and parses the
\fI$INVOCATION_ID\fR
environment variable that the service manager sets when activating a service, see
\fBsystemd.exec\fR(5)
for details\&. The ID is cached internally\&. In future a different mechanism to determine the invocation ID may be added\&.
.PP
Note that
\fBsd_id128_get_boot()\fR
and
\fBsd_id128_get_invocation()\fR
always return UUID v4 compatible IDs\&.
\fBsd_id128_get_machine()\fR
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
\fBmachine-id\fR(5)\&.
.PP
For more information about the
"sd_id128_t"
type see
\fBsd-id128\fR(3)\&.
.SH "RETURN VALUE"
.PP
The two calls return 0 on success (in which case
\fIret\fR
is filled in), or a negative errno\-style error code\&.
.SH "NOTES"
.PP
The
\fBsd_id128_get_machine()\fR,
\fBsd_id128_get_boot()\fR
and
\fBsd_id128_get_invocation()\fR
interfaces are available as a shared library, which can be compiled and linked to with the
"libsystemd"\ \&\fBpkg-config\fR(1)
file\&.
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1),
\fBsd-id128\fR(3),
\fBmachine-id\fR(5),
\fBsystemd.exec\fR(5),
\fBsd_id128_randomize\fR(3),
\fBrandom\fR(4)