man/sd_id128_get_machine.3

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   2 .TH "SD_ID128_GET_MACHINE" "3" "" "systemd 219" "sd_id128_get_machine"
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   8 .\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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  22 .SH "NAME"
  23 sd_id128_get_machine, sd_id128_get_boot \- Retrieve 128\-bit IDs
  24 .SH "SYNOPSIS"
  25 .sp
  26 .ft B
  27 .nf
  28 #include <systemd/sd\-id128\&.h>
  29 .fi
  30 .ft
  31 .HP \w'int\ sd_id128_get_machine('u
  32 .BI "int sd_id128_get_machine(sd_id128_t\ *" "ret" ");"
  33 .HP \w'int\ sd_id128_get_boot('u
  34 .BI "int sd_id128_get_boot(sd_id128_t\ *" "ret" ");"
  35 .SH "DESCRIPTION"
  36 .PP
  37 \fBsd_id128_get_machine()\fR
  38 returns the machine ID of the executing host\&. This reads and parses the
  39 \fBmachine-id\fR(5)
  40 file\&. This function caches the machine ID internally to make retrieving the machine ID a cheap operation\&.
  41 .PP
  42 \fBsd_id128_get_boot()\fR
  43 returns the boot ID of the executing kernel\&. This reads and parses the
  44 /proc/sys/kernel/random/boot_id
  45 file exposed by the kernel\&. It is randomly generated early at boot and is unique for every running kernel instance\&. See
  46 \fBrandom\fR(4)
  47 for more information\&. This function also internally caches the returned ID to make this call a cheap operation\&.
  48 .PP
  49 Note that
  50 \fBsd_id128_get_boot()\fR
  51 always returns a UUID v4 compatible ID\&.
  52 \fBsd_id128_get_machine()\fR
  53 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
  54 \fBmachine-id\fR(5)\&.
  55 .PP
  56 For more information about the
  57 "sd_id128_t"
  58 type see
  59 \fBsd-id128\fR(3)\&.
  60 .SH "RETURN VALUE"
  61 .PP
  62 The two calls return 0 on success (in which case
  63 \fIret\fR
  64 is filled in), or a negative errno\-style error code\&.
  65 .SH "NOTES"
  66 .PP
  67 The
  68 \fBsd_id128_get_machine()\fR
  69 and
  70 \fBsd_id128_get_boot()\fR
  71 interfaces are available as a shared library, which can be compiled and linked to with the
  72 "libsystemd"\ \&\fBpkg-config\fR(1)
  73 file\&.
  74 .SH "SEE ALSO"
  75 .PP
  76 \fBsystemd\fR(1),
  77 \fBsd-id128\fR(3),
  78 \fBmachine-id\fR(5),
  79 \fBrandom\fR(4),
  80 \fBsd_id128_randomize\fR(3)